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Deshpande RS, Langham MC, Lee H, Kamona N, Wehrli FW. Quantification of whole-organ individual and bilateral renal metabolic rate of oxygen. Magn Reson Med 2024; 91:2057-2073. [PMID: 38146669 PMCID: PMC10950521 DOI: 10.1002/mrm.29981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/21/2023] [Accepted: 12/01/2023] [Indexed: 12/27/2023]
Abstract
PURPOSE Renal metabolic rate of oxygen (rMRO2 ) is a potentially important biomarker of kidney function. The key parameters for rMRO2 quantification include blood flow rate (BFR) and venous oxygen saturation (SvO2 ) in a draining vessel. Previous approaches to quantify renal metabolism have focused on the single organ. Here, both kidneys are considered as one unit to quantify bilateral rMRO2 . A pulse sequence to facilitate bilateral rMRO2 quantification is introduced. METHODS To quantify bilateral rMRO2 , measurements of BFR and SvO2 are made along the inferior vena cava (IVC) at suprarenal and infrarenal locations. From the continuity equation, these four parameters can be related to derive an expression for bilateral rMRO2 . The recently reported K-MOTIVE pulse sequence was implemented at four locations: left kidney, right kidney, suprarenal IVC, and infrarenal IVC. A dual-band variant of K-MOTIVE (db-K-MOTIVE) was developed by incorporating simultaneous-multi-slice imaging principles. The sequence simultaneously measures BFR and SvO2 at suprarenal and infrarenal locations in a single pass of 21 s, yielding bilateral rMRO2 . RESULTS SvO2 and BFR are higher in suprarenal versus infrarenal IVC, and the renal veins are highly oxygenated (SvO2 >90%). Bilateral rMRO2 quantified in 10 healthy subjects (8 M, 30 ± 8 y) was found to be 291 ± 247 and 349 ± 300 (μmolO2 /min)/100 g, derived from K-MOTIVE and db-K-MOTIVE, respectively. In comparison, total rMRO2 from combining left and right was 329 ± 273 (μmolO2 /min)/100 g. CONCLUSION The present work demonstrates that bilateral rMRO2 quantification is feasible with fair reproducibility and physiological plausibility. The indirect method is a promising approach to compute bilateral rMRO2 when individual rMRO2 quantification is difficult.
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Affiliation(s)
- Rajiv S. Deshpande
- Laboratory for Structural Physiologic and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, PA, USA
| | - Michael C. Langham
- Laboratory for Structural Physiologic and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, PA, USA
| | - Hyunyeol Lee
- Laboratory for Structural Physiologic and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, PA, USA
- School of Electronic and Electrical Engineering, Kyungpook National University, Daegu, South Korea
| | - Nada Kamona
- Laboratory for Structural Physiologic and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, PA, USA
| | - Felix W. Wehrli
- Laboratory for Structural Physiologic and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, PA, USA
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Eirin A, Chade AR, Lerman LO. Kidney Intrinsic Mechanisms as Novel Targets in Renovascular Hypertension. Hypertension 2024; 81:206-217. [PMID: 37869904 PMCID: PMC10842320 DOI: 10.1161/hypertensionaha.123.21362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2023]
Abstract
Almost a hundred years have passed since obstruction of the renal artery has been recognized to raise blood pressure. By now chronic renovascular disease (RVD) due to renal artery stenosis is recognized as a major source of renovascular hypertension and renal disease. In some patients, RVD unaccompanied by noteworthy renal dysfunction or blood pressure elevation may be incidentally identified during peripheral angiography. Nevertheless, in others, RVD might present as a progressive disease associated with diffuse atherosclerosis, leading to loss of renal function, renovascular hypertension, hemodynamic compromise, and a magnified risk for cardiovascular morbidity and mortality. Atherosclerotic RVD leads to renal atrophy, inflammation, and hypoxia but represents a potentially treatable cause of chronic renal failure because until severe fibrosis sets in the ischemic kidney, it retains a robust potential for vascular and tubular regeneration. This remarkable recovery capacity of the kidney begs for early diagnosis and treatment. However, accumulating evidence from both animal studies and randomized clinical trials has convincingly established the inadequate efficacy of renal artery revascularization to fully restore renal function or blood pressure control and has illuminated the potential of therapies targeted to the ischemic renal parenchyma to instigate renal regeneration. Some of the injurious mechanisms identified as potential therapeutic targets included oxidative stress, microvascular disease, inflammation, mitochondrial injury, and cellular senescence. This review recapitulates the intrinsic mechanisms that orchestrate renal damage and recovery in RVD and can be harnessed to introduce remedial opportunities.
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Affiliation(s)
- Alfonso Eirin
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA
| | - Alejandro R. Chade
- Department of Medical Pharmacology and Physiology, University of Missouri-Columbia, MO
| | - Lilach O. Lerman
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA
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Aggarwal A, Das CJ, Sharma S. Recent advances in imaging techniques of renal masses. World J Radiol 2022; 14:137-150. [PMID: 35978979 PMCID: PMC9258310 DOI: 10.4329/wjr.v14.i6.137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/04/2022] [Accepted: 06/17/2022] [Indexed: 02/06/2023] Open
Abstract
Multiphasic multidetector computed tomography (CT) forms the mainstay for the characterization of renal masses whereas magnetic resonance imaging (MRI) acts as a problem-solving tool in some cases. However, a few of the renal masses remain indeterminate even after evaluation by conventional imaging methods. To overcome the deficiency in current imaging techniques, advanced imaging methods have been devised and are being tested. This review will cover the role of contrast-enhanced ultrasonography, shear wave elastography, dual-energy CT, perfusion CT, MR perfusion, diffusion-weighted MRI, blood oxygen level-dependent MRI, MR spectroscopy, positron emission tomography (PET)/prostate-specific membrane antigen-PET in the characterization of renal masses.
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Affiliation(s)
- Ankita Aggarwal
- Department of Radiology, Vardhman Mahavir Medical College& Safdarjung Hospital, Delhi 110029, India
| | - Chandan J Das
- Department of Radiodiagnosis and Interventional Radiology, All India Institute of Medical Sciences, Delhi 110029, India
| | - Sanjay Sharma
- Department of Radiology (RPC), All India Institute of Medical Sciences, New Delhi 110029, India
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Laursen JC, Søndergaard-Heinrich N, Haddock B, Rasmussen IKB, Hansen CS, Larsson HBW, Groop PH, Bjornstad P, Frimodt-Møller M, Andersen UB, Rossing P. Kidney oxygenation, perfusion and blood flow in people with and without type 1 diabetes. Clin Kidney J 2022; 15:2072-2080. [PMID: 36825032 PMCID: PMC9942445 DOI: 10.1093/ckj/sfac145] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Indexed: 11/12/2022] Open
Abstract
Background We used magnetic resonance imaging (MRI) to study kidney energetics in persons with and without type 1 diabetes (T1D). Methods In a cross-sectional study, 15 persons with T1D and albuminuria and 15 non-diabetic controls (CONs) underwent multiparametric MRI (3 Tesla Philips Scanner) to quantify renal cortical and medullary oxygenation (R2*, higher values correspond to higher deoxyhaemoglobin concentration), renal perfusion (arterial spin labelling) and renal artery blood flow (phase contrast). Analyses were adjusted for age, sex, systolic blood pressure, plasma haemoglobin, body mass index and estimated glomerular filtration rate (eGFR). Results Participants with T1D had a higher median (Q1; Q3) urine albumin creatinine ratio (UACR) than CONs [46 (21; 58) versus 4 (3; 6) mg/g; P < .0001] and a lower mean ± SD eGFR (73 ± 32 mL/min/1.73 m2 versus 88 ± 15 mL/min/1.73 m2; P = .12), although not significantly. Mean medullary R2* was lower in T1D (34 ± 6/s versus 38 ± 5/s; P < .01) corresponding to a higher oxygenation. R2* was not different in the cortex. Cortical perfusion was lower in T1D (163 ± 40 versus 224 ± 49 mL/100 g/min; P < .001). Renal artery blood flow was lower in T1D than in CONs (360 ± 130 versus 430 ± 113 mL/min; P = .05). In T1D, lower cortical oxygenation and renal artery blood flow were both associated with higher UACR and lower eGFR (P < .05). Conclusions Participants with T1D and albuminuria exhibited higher medullary oxygenation than CONs, despite lower cortical perfusion and renal artery blood flow. This might reflect perturbed kidney energetics leading to a higher setpoint of medullary oxygenation in T1D. Lower cortical oxygenation and renal artery blood flow were associated with higher UACR and lower eGFR in T1D.
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Affiliation(s)
| | - Niels Søndergaard-Heinrich
- Complications Research, Steno Diabetes Center Copenhagen, Copenhagen, Denmark
- Department of Clinical Medicine, the Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
| | - Bryan Haddock
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Ida Kirstine Bull Rasmussen
- Complications Research, Steno Diabetes Center Copenhagen, Copenhagen, Denmark
- Department of Clinical Medicine, the Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
| | | | - Henrik Bo Wiberg Larsson
- Department of Clinical Medicine, the Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Per-Henrik Groop
- FinnDiane Study Group, Folkhälsan Research Center, Helsinki, Finland
- Department of Nephrology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Department of Medicine, Central Clinical School, Monash University, Melbourne, Australia
| | - Petter Bjornstad
- Department of Medicine, Division of Renal Diseases and Hypertension, Department of Paediatrics, Section of Endocrinology, University of Colorado School of Medicine, CO, USA
| | | | | | - Peter Rossing
- Complications Research, Steno Diabetes Center Copenhagen, Copenhagen, Denmark
- Department of Clinical Medicine, the Faculty of Health and Medical Science, University of Copenhagen, Copenhagen, Denmark
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Zhao L, Li G, Meng F, Sun Z, Liu J. Cortical and medullary oxygenation evaluation of kidneys with renal artery stenosis by BOLD-MRI. PLoS One 2022; 17:e0264630. [PMID: 35271618 PMCID: PMC8912187 DOI: 10.1371/journal.pone.0264630] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 02/14/2022] [Indexed: 11/18/2022] Open
Abstract
Aim Blood oxygen level–dependent magnetic resonance imaging (BOLD-MRI) can measure deoxyhemoglobin content. This study aims to evaluate the capacity of BOLD-MRI, which is possible to evaluate the oxygenation state of kidneys with renal artery stenosis (RAS). Materials and methods We performed BOLD-MRI for 40 patients with RAS and for 30 healthy volunteers. We then performed post-scan processing and analysis of manually drawn regions of interest to determine R2* values (relaxation rates) for the renal cortex and medulla. We compared R2* values in patients with RAS with those in the control group, and also compared these values for subgroups with varying degrees of stenosis. Results Medulla R2* values were higher than cortex R2* values in the control group. There was no significant difference in R2* values for different segments (upper, middle, lower) of the kidneys. Both cortex and medulla R2* values in patients with RAS were significantly higher than corresponding R2* values in the control group (P < 0.05), and BOLD-MRI was more sensitive to changes in the R2* values in the medulla than in the cortex. Among different subgroups in the RAS group, the medulla R2* values were significantly higher in kidneys with severe stenosis than in those with no obvious obstruction, mild stenosis, or moderate stenosis (P < 0.05). Conclusion BOLD-MRI is an effective, noninvasive method for evaluating kidney oxygenation, which is important for proper treatment in RAS. It is sufficiently sensitive for detecting medulla ischemia and anoxia of the kidneys.
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Affiliation(s)
- Long Zhao
- Department of Radiology, Beijing Anzhen Hospital, Beijing, China
| | - Guoqi Li
- Energy conservation and environmental protection division, Aerospace HIWING Security Technology Engineering Co., Ltd, Beijing, China
| | - Fanyu Meng
- International Cooperation Office, Beijing Anzhen Hospital, Beijing, China
| | - Zhonghua Sun
- Discipline of Medical Radiation Science, Curtin Medical School, Curtin University, Perth, Australia
| | - Jiayi Liu
- Department of Radiology, Beijing Anzhen Hospital, Beijing, China
- * E-mail:
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Emergent players in renovascular disease. Clin Sci (Lond) 2022; 136:239-256. [PMID: 35129198 DOI: 10.1042/cs20210509] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 01/25/2022] [Accepted: 01/26/2022] [Indexed: 02/07/2023]
Abstract
Renovascular disease (RVD) remains a common etiology of secondary hypertension. Recent clinical trials revealed unsatisfactory therapeutic outcomes of renal revascularization, leading to extensive investigation to unravel key pathophysiological mechanisms underlying irreversible functional loss and structural damage in the chronically ischemic kidney. Research studies identified complex interactions among various players, including inflammation, fibrosis, mitochondrial injury, cellular senescence, and microvascular remodeling. This interplay resulted in a shift of our understanding of RVD from a mere hemodynamic disorder to a pro-inflammatory and pro-fibrotic pathology strongly influenced by systemic diseases like metabolic syndrome (MetS), hypertension, diabetes mellitus, and hyperlipidemia. Novel diagnostic approaches have been tested for early detection and follow-up of RVD progression, using new imaging techniques and biochemical markers of renal injury and dysfunction. Therapies targeting some of the pathological pathways governing the development of RVD have shown promising results in animal models, and a few have moved from bench to clinical research. This review summarizes evolving understanding in chronic ischemic kidney injury.
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Lee SK, Lee J, Jang S, Lee E, Jeon CY, Lim KS, Jin YB, Choi J. Quantification of renal T2 relaxation rate by use of blood oxygen level-dependent magnetic resonance imaging before and after furosemide administration in healthy Beagles. Am J Vet Res 2021; 82:880-889. [PMID: 34669496 DOI: 10.2460/ajvr.82.11.880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To assess the feasibility of blood oxygen level-dependent (BOLD) MRI for measurement of the renal T2* relaxation rate (R2*; proxy for renal oxygenation) before and after furosemide administration and to evaluate the reliability and repeatability of those measurements in healthy dogs. ANIMALS 8 healthy adult Beagles (4 males and 4 females). PROCEDURES Each dog was anesthetized and underwent BOLD MRI before (baseline) and 3 minutes after administration of furosemide (1 mg/kg, IV) twice, with a 1-week interval between scanning sessions. Mapping software was used to process MRI images and measure R2* and the difference in R2* (ΔR2*) before and after furosemide administration. The intraclass correlation coefficient was calculated to assess measurement reliability, and the coefficient of variation and Bland-Altman method were used to assess measurement repeatability. RESULTS Mean ± SD baseline R2* in the renal medulla (24.5 ± 3.8 seconds-1) was significantly greater than that in the renal cortex (20.6 ± 2.7 seconds-1). Mean R2* in the renal cortex (18.6 ± 2.6 seconds-1) and medulla (17.8 ± 1.5 seconds-1) decreased significantly after furosemide administration. Mean ΔR2* in the medulla (6.7 ± 2.4 seconds-1) was significantly greater than that in the renal cortex (2.1 ± 0.7 seconds-1). All R2* and ΔR2* values had good or excellent reliability and repeatability, except the cortical ΔR2*, which had poor repeatability. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that BOLD MRI, when performed before and after furosemide administration, was noninvasive and highly reliable and repeatable for dynamic evaluation of renal oxygenation in healthy dogs.
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Affiliation(s)
- Sang-Kwon Lee
- From the College of Veterinary Medicine, Kyungpook National University, Daegu 41566, South Korea
| | - Juryeong Lee
- the College of Veterinary Medicine and BK21 Plus Project Team, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Seolyn Jang
- the College of Veterinary Medicine and BK21 Plus Project Team, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Eunji Lee
- the College of Veterinary Medicine and BK21 Plus Project Team, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Chang-Yeop Jeon
- National Primate Research Center and Futuristic Animal Resource and Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju 28116, Republic of Korea
| | - Kyung-Seob Lim
- National Primate Research Center and Futuristic Animal Resource and Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju 28116, Republic of Korea
| | - Yeung Bae Jin
- the College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Republic of Korea
| | - Jihye Choi
- the Department of Veterinary Medical Imaging, College of Veterinary Medicine, Seoul National University, Seoul 08826, South Korea
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Laursen JC, Søndergaard-Heinrich N, de Melo JML, Haddock B, Rasmussen IKB, Safavimanesh F, Hansen CS, Størling J, Larsson HBW, Groop PH, Frimodt-Møller M, Andersen UB, Rossing P. Acute effects of dapagliflozin on renal oxygenation and perfusion in type 1 diabetes with albuminuria: A randomised, double-blind, placebo-controlled crossover trial. EClinicalMedicine 2021; 37:100895. [PMID: 34386735 PMCID: PMC8343250 DOI: 10.1016/j.eclinm.2021.100895] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 04/22/2021] [Accepted: 04/23/2021] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Inhibitors of the sodium-glucose cotransporter 2 (SGLT2) slow the progression of diabetic kidney disease, possibly by reducing the proximal tubule transport workload with subsequent improvement of renal oxygenation. We aimed to test this hypothesis in individuals with type 1 diabetes and albuminuria. METHODS A randomised, double-blind, placebo-controlled, crossover trial with a single 50 mg dose of the SGLT2 inhibitor dapagliflozin and placebo in random order, separated by a two-week washout period. Magnetic resonance imaging (MRI) was used to assess renal R2* (a low value corresponds to a high tissue oxygenation), renal perfusion (arterial spin labelling) and renal artery flow (phase contrast imaging) at baseline, three- and six hours from tablet ingestion. Exploratory outcomes, including baroreflex sensitivity, peripheral blood oxygen saturation, peripheral blood mononuclear cell mitochondrial oxygen consumption rate, and biomarkers of inflammation were evaluated at baseline and 12 h from medication. The study is registered in the EU Clinical Trials Register (EudraCT 2019-004,557-92), on ClinicalTrials.gov (NCT04193566), and is completed. FINDINGS Between February 3, 2020 and October 23, 2020, 31 individuals were screened, and 19 eligible individuals were randomised. Three dropped out before receiving any of the interventions and one dropped out after receiving only placebo. We included 15 individuals (33% female) in the per-protocol analysis with a mean age of 58 (SD 14) years, median urinary albumin creatinine ratio of 46 [IQR 21-58] mg/g and an eGFR of 73 (32) ml/min/1·73m2. The mean changes in renal cortical R2* from baseline to six hours were for dapagliflozin -1·1 (SD 0·7) s-1 and for placebo +1·3 (0·7) s-1, resulting in a difference between interventions of -2·3 s-1 [95% CI -4·0 to -0·6]; p = 0·012. No between-intervention differences were found in any other MRI outcomes, physiological parameters or exploratory outcomes. There were no adverse events. INTERPRETATION A single dose of 50 mg dapagliflozin acutely improved renal cortical R2* without changing renal perfusion or blood flow. This suggests improved renal cortical oxygenation due to a reduced tubular transport workload in the proximal tubules. Such improved oxygenation may in part explain the long-term beneficial renal effects seen with SGLT2 inhibitors, but it remains to be determined whether the observed effects can be achieved with lower doses, with chronic treatment and if they occur in type 2 diabetes as well.
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Affiliation(s)
| | | | | | - Bryan Haddock
- Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Copenhagen University Hospital, Denmark
| | | | | | | | | | - Henrik Bo Wiberg Larsson
- Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Copenhagen University Hospital, Denmark
| | - Per-Henrik Groop
- Folkhälsan Research Center, Helsinki, Finland
- Department of Nephrology, University of Helsinki and Helsinki University Hospital, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Finland
- Department of Medicine, Central Clinical School, Monash University, Melbourne, Australia
| | | | - Ulrik Bjørn Andersen
- Steno Diabetes Center Copenhagen, Denmark
- University of Copenhagen, Denmark
- Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Copenhagen University Hospital, Denmark
- Folkhälsan Research Center, Helsinki, Finland
- Department of Nephrology, University of Helsinki and Helsinki University Hospital, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Finland
- Department of Medicine, Central Clinical School, Monash University, Melbourne, Australia
| | - Peter Rossing
- Steno Diabetes Center Copenhagen, Denmark
- University of Copenhagen, Denmark
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Jiang K, Ferguson CM, Lerman LO. Noninvasive assessment of renal fibrosis by magnetic resonance imaging and ultrasound techniques. Transl Res 2019; 209:105-120. [PMID: 31082371 PMCID: PMC6553637 DOI: 10.1016/j.trsl.2019.02.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/12/2019] [Accepted: 02/20/2019] [Indexed: 02/06/2023]
Abstract
Renal fibrosis is a useful biomarker for diagnosis and guidance of therapeutic interventions of chronic kidney disease (CKD), a worldwide disease that affects more than 10% of the population and is one of the major causes of death. Currently, tissue biopsy is the gold standard for assessment of renal fibrosis. However, it is invasive, and prone to sampling error and observer variability, and may also result in complications. Recent advances in diagnostic imaging techniques, including magnetic resonance imaging (MRI) and ultrasonography, have shown promise for noninvasive assessment of renal fibrosis. These imaging techniques measure renal fibrosis by evaluating its impacts on the functional, mechanical, and molecular properties of the kidney, such as water mobility by diffusion MRI, tissue hypoxia by blood oxygenation level dependent MRI, renal stiffness by MR and ultrasound elastography, and macromolecule content by magnetization transfer imaging. Other MR techniques, such as T1/T2 mapping and susceptibility-weighted imaging have also been explored for measuring renal fibrosis. Promising findings have been reported in both preclinical and clinical studies using these techniques. Nevertheless, limited specificity, sensitivity, and practicality in these techniques may hinder their immediate application in clinical routine. In this review, we will introduce methodologies of these techniques, outline their applications in fibrosis imaging, and discuss their limitations and pitfalls.
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Affiliation(s)
- Kai Jiang
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
| | | | - Lilach O Lerman
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota.
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Li H, Cao W, Zhang X, Sun B, Jiang S, Li J, Liu C, Yin W, Wu Y, Liu T, Yao D, Luo C. BOLD-fMRI reveals the association between renal oxygenation and functional connectivity in the aging brain. Neuroimage 2019; 186:510-517. [DOI: 10.1016/j.neuroimage.2018.11.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 11/19/2018] [Accepted: 11/20/2018] [Indexed: 01/23/2023] Open
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11
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Lal H, Mohamed E, Soni N, Yadav P, Jain M, Bhadauria D, Kaul A, Prasad N, Gupta A, Sharma RK. Role of Blood Oxygen Level-dependent MRI in Differentiation of Acute Renal Allograft Dysfunction. Indian J Nephrol 2019; 28:441-447. [PMID: 30647498 PMCID: PMC6309386 DOI: 10.4103/ijn.ijn_43_18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Early graft dysfunction after renal transplantation manifests as acute rejection (AR) or acute tubular necrosis (ATN). Blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging is a noninvasive method of assessing tissue oxygenation, which may be useful for predicting acute allograft dysfunction. This was a prospective study involving 40 patients scheduled for renal transplantation from August 2012 to August 2014. In addition, 15 healthy donors were also enrolled in this study. All recipients underwent BOLD MR imaging (MRI) and R2* mapping 10–20 days after transplant, and additionally within 48 h of biopsy if there was any evidence of graft dysfunction. The healthy donors underwent BOLD MRI 1–2 days before surgery. The biopsies were grouped into AR, ATN, and no evidence of AR or ATN. The mean medullary R2*, cortical R2*, corticomedullary gradient, and medullary: cortical R2* ratio were compared between groups using one-way analysis of variance. Spearman's correlation and multinomial linear regression were applied to determine the influence factors of R2* value. Overall, nine patients had graft dysfunction. Six were reported as AR, two as ATN, and one as no evidence of ATN or rejection. The mean medullary and cortical R2* were significantly higher in ATN group compared with AR and normal group, whereas the mean medullary and cortical R2* of AR group were significantly lower than normal group. The corticomedullary gradient of AR group was significantly lower compared with ATN and normal group. Medullary R2*:cortical R2* ratio was significantly lower in AR group compared with normal group. No significant difference was noted between the 15 donors and patients with normal graft function. R2* values on BOLD MRI are significantly decreased in AR allografts and increased in an early stage of ATN allografts, suggesting that BOLD MRI can become a valuable tool for discriminating between AR and ATN.
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Affiliation(s)
- Hira Lal
- Department of Radiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Ezaz Mohamed
- Department of Radiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Neelam Soni
- Department of Radiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Priyank Yadav
- Department of Urology and Renal Transplantation, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Manoj Jain
- Department of Pathology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Dharmendra Bhadauria
- Department of Nephrology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Anupma Kaul
- Department of Nephrology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Narayan Prasad
- Department of Nephrology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - Amit Gupta
- Department of Nephrology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
| | - R K Sharma
- Department of Nephrology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
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Haddock BT, Francis ST, Larsson HB, Andersen UB. Assessment of Perfusion and Oxygenation of the Human Renal Cortex and Medulla by Quantitative MRI during Handgrip Exercise. J Am Soc Nephrol 2018; 29:2510-2517. [PMID: 30206141 PMCID: PMC6171273 DOI: 10.1681/asn.2018030272] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 08/08/2018] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Renal flow abnormalities are believed to play a central role in the pathogenesis of nephropathy and in primary and secondary hypertension, but are difficult to measure in humans. Handgrip exercise is known to reduce renal arterial flow (RAF) by means of increased renal sympathetic nerve activity. METHODS To monitor medullary and cortical oxygenation under handgrip exercise-reduced perfusion, we used contrast- and radiation-free magnetic resonance imaging (MRI) to measure regional changes in renal perfusion and blood oxygenation in ten healthy normotensive individuals during handgrip exercise. We used phase-contrast MRI to measure RAF, arterial spin labeling to measure perfusion, and both changes in transverse relaxation time (T2*) and dynamic blood oxygenation level-dependent imaging to measure blood oxygenation. RESULTS Handgrip exercise induced a significant decrease in RAF. In the renal medulla, this was accompanied by an increase of oxygenation (reflected by an increase in T2*) despite a significant drop in medullary perfusion; the renal cortex showed a significant decrease in both perfusion and oxygenation. We also found a significant correlation (R2=0.8) between resting systolic BP and the decrease in RAF during handgrip exercise. CONCLUSIONS Renal MRI measurements in response to handgrip exercise were consistent with a sympathetically mediated decrease in RAF. In the renal medulla, oxygenation increased despite a reduction in perfusion, which we interpreted as the result of decreased GFR and a subsequently reduced reabsorptive workload. Our results further indicate that the renal flow response's sensitivity to sympathetic activation is correlated with resting BP, even within a normotensive range.
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Affiliation(s)
- Bryan Thomas Haddock
- Department of Clinical Physiology, Nuclear Medicine and Positron Emission Tomography, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark; and
| | - Susan T. Francis
- Sir Peter Mansfield Imaging Centre School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - Henrik B.W. Larsson
- Department of Clinical Physiology, Nuclear Medicine and Positron Emission Tomography, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark; and
| | - Ulrik B. Andersen
- Department of Clinical Physiology, Nuclear Medicine and Positron Emission Tomography, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark; and
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13
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Gondalia R, Vernuccio F, Marin D, Bashir MR. The role of MR imaging in the assessment of renal allograft vasculature. Abdom Radiol (NY) 2018; 43:2589-2596. [PMID: 29700591 DOI: 10.1007/s00261-018-1611-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Renal allograft dysfunction after transplantation is a relatively common occurrence with various potential etiologies. Vascular etiologies are of particular importance as early surgical or minimally invasive intervention can, in some cases, salvage the graft. Diagnosis of vascular pathology resulting in allograft dysfunction requires a thorough workup, of which imaging is a key component. Generally, ultrasound is the first-line imaging modality. More recently, MRI has been shown to be an effective and safe modality for diagnosis of vascular pathology after renal transplantation, particularly for diagnosis of transplant renal artery stenosis. This review will summarize imaging modalities that are most commonly used in evaluating vascular pathology after renal transplantation, with a focus on the various contrast- and non-contrast-enhanced MR techniques described in the literature and used at our institution. Of particular interest is the relatively recent utilization of the non-gadolinium containing iron-based contrast agent, ferumoxytol, in time-resolved contrast-enhanced MR angiography.
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Affiliation(s)
- Raj Gondalia
- Department of Radiology, Duke University Medical Center, Box 3808 Erwin Road, Durham, NC, 27710, USA.
| | - Federica Vernuccio
- Department of Radiology, Duke University Medical Center, Box 3808 Erwin Road, Durham, NC, 27710, USA
- Section of Radiology -Di.Bi.Med, University Hospital "Paolo Giaccone", 90129, Palermo, Italy
| | - Daniele Marin
- Department of Radiology, Duke University Medical Center, Box 3808 Erwin Road, Durham, NC, 27710, USA
| | - Mustafa R Bashir
- Department of Radiology, Duke University Medical Center, Box 3808 Erwin Road, Durham, NC, 27710, USA
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14
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Taffel MT, Nikolaidis P, Beland MD, Blaufox MD, Dogra VS, Goldfarb S, Gore JL, Harvin HJ, Heilbrun ME, Heller MT, Khatri G, Preminger GM, Purysko AS, Smith AD, Wang ZJ, Weinfeld RM, Wong-You-Cheong JJ, Remer EM, Lockhart ME. ACR Appropriateness Criteria ® Renal Transplant Dysfunction. J Am Coll Radiol 2018; 14:S272-S281. [PMID: 28473084 DOI: 10.1016/j.jacr.2017.02.034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 02/20/2017] [Accepted: 02/21/2017] [Indexed: 02/06/2023]
Abstract
Renal transplantation is the treatment of choice in patients with end-stage renal disease because the 5-year survival rates range from 72% to 99%. Although graft survival has improved secondary to the introduction of newer immunosuppression drugs and the advancements in surgical technique, various complications still occur. Ultrasound is the first-line imaging modality for the evaluation of renal transplants in the immediate postoperative period and for long-term follow-up. In addition to depicting many of the potential complications of renal transplantation, ultrasound can also guide therapeutic interventions. Nuclear medicine studies, CT, and MRI are often helpful as complementary examinations for specific indications. Angiography remains the reference standard for vascular complications and is utilized to guide nonsurgical intervention. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.
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Affiliation(s)
| | - Myles T Taffel
- Principal Author, George Washington University Hospital, Washington, District of Columbia.
| | - Paul Nikolaidis
- Panel Vice-chair, Northwestern University, Chicago, Illinois
| | | | - M Donald Blaufox
- Albert Einstein College of Medicine, Bronx, New York; Society of Nuclear Medicine and Molecular Imaging
| | - Vikram S Dogra
- University of Rochester Medical Center, Rochester, New York
| | - Stanley Goldfarb
- University of Pennsylvania School of Medicine, Philadelphia; Pennsylvania, American Society of Nephrology
| | - John L Gore
- University of Washington, Seattle, Washington; American Urological Association
| | | | | | | | | | - Glenn M Preminger
- Duke University Medical Center, Durham, North Carolina; American Urological Association
| | | | - Andrew D Smith
- The University of Mississippi Medical Center, Jackson, Mississippi
| | - Zhen J Wang
- University of California San Francisco School of Medicine, San Francisco, California
| | - Robert M Weinfeld
- Oakland University William Beaumont School of Medicine, Troy, Michigan
| | | | | | - Mark E Lockhart
- Panel Chair, University of Alabama at Birmingham, Birmingham, Alabama
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15
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Hall ME, Jordan JH, Juncos LA, Hundley WG, Hall JE. BOLD magnetic resonance imaging in nephrology. Int J Nephrol Renovasc Dis 2018; 11:103-112. [PMID: 29559807 PMCID: PMC5856054 DOI: 10.2147/ijnrd.s112299] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Magnetic resonance (MR) imaging, a non-invasive modality that provides anatomic and physiologic information, is increasingly used for diagnosis of pathophysiologic conditions and for understanding renal physiology in humans. Although functional MR imaging methods were pioneered to investigate the brain, they also offer powerful techniques for investigation of other organ systems such as the kidneys. However, imaging the kidneys provides unique challenges due to potential complications from contrast agents. Therefore, development of non-contrast techniques to study kidney anatomy and physiology is important. Blood oxygen level-dependent (BOLD) MR is a non-contrast imaging technique that provides functional information related to renal tissue oxygenation in various pathophysiologic conditions. Here we discuss technical considerations, clinical uses and future directions for use of BOLD MR as well as complementary MR techniques to better understand renal pathophysiology. Our intent is to summarize kidney BOLD MR applications for the clinician rather than focusing on the complex physical challenges that functional MR imaging encompasses; however, we briefly discuss some of those issues.
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Affiliation(s)
- Michael E Hall
- Department of Medicine, University of Mississippi Medical Center, Jackson, MS, USA.,Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS, USA
| | - Jennifer H Jordan
- Department of Internal Medicine, Section on Cardiovascular Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Luis A Juncos
- Department of Medicine, University of Mississippi Medical Center, Jackson, MS, USA.,Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS, USA
| | - W Gregory Hundley
- Department of Internal Medicine, Section on Cardiovascular Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - John E Hall
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS, USA
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16
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Chen F, Li S, Sun D. Methods of Blood Oxygen Level-Dependent Magnetic Resonance Imaging Analysis for Evaluating Renal Oxygenation. Kidney Blood Press Res 2018. [PMID: 29539614 DOI: 10.1159/000488072] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently been utilized as a noninvasive tool for evaluating renal oxygenation. Several methods have been proposed for analyzing BOLD images. Regional ROI selection is the earliest and most widely used method for BOLD analysis. In the last 20 years, many investigators have used this method to evaluate cortical and medullary oxygenation in patients with ischemic nephropathy, hypertensive nephropathy, diabetic nephropathy, chronic kidney disease (CKD), acute kidney injury and renal allograft rejection. However, clinical trials of BOLD MRI using regional ROI selection revealed that it was difficult to distinguish the renal cortico-medullary zones with this method, and that it was susceptible to observer variability. To overcome these deficiencies, several new methods were proposed for analyzing BOLD images, including the compartmental approach, fractional hypoxia method, concentric objects (CO) method and twelve-layer concentric objects (TLCO) method. The compartmental approach provides an algorithm to judge whether the pixel belongs to the cortex or medulla. Fractional kidney hypoxia, measured by using BOLD MRI, was negatively correlated with renal blood flow, tissue perfusion and glomerular filtration rate (GFR) in patients with atherosclerotic renal artery stenosis. The CO method divides the renal parenchyma into six or twelve layers of thickness in each coronal slice of BOLD images and provides a R2* radial profile curve. The slope of the R2* curve associated positively with eGFR in CKD patients. Indeed, each method invariably has advantages and disadvantages, and there is generally no consensus method so far. Undoubtedly, analytic approaches for BOLD MRI with better reproducibility would assist clinicians in monitoring the degree of kidney hypoxia and thus facilitating timely reversal of tissue hypoxia.
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Affiliation(s)
- Fen Chen
- Department of Nephrology, Xuzhou Medical University, Xuzhou, China
| | - Shulin Li
- Department of Nephrology, Xuzhou Medical University, Xuzhou, China.,Department of Nephrology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
| | - Dong Sun
- Department of Nephrology, Xuzhou Medical University, Xuzhou, China.,Department of Nephrology, Affiliated Hospital of Xuzhou Medical University, Xuzhou, China
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17
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Abstract
Renovascular disease (RVD), which is prevalent in the elderly, significantly increases cardiovascular risk and can progressively deteriorate renal function. The loss of renal function in patients with RVD is associated with a progressive dysfunction, damage, and loss of renal microvessels, which can be combined with decreased renal bioavailability of vascular endothelial growth factor (VEGF) and a defective vascular repair and proliferation. This association has been the impetus for recent efforts that have focused on developing methods to stop the progression of renal injury by protecting the renal microvasculature. This mini-review focuses on recent studies supporting potential applications of VEGF therapy for the kidney and discusses underlying mechanisms of renoprotection.
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Affiliation(s)
- Erika Guise
- Department of Physiology and Biophysics, University of Mississippi Medical Center , Jackson, Mississippi
| | - Alejandro R Chade
- Department of Physiology and Biophysics, University of Mississippi Medical Center , Jackson, Mississippi.,Department of Medicine, University of Mississippi Medical Center , Jackson, Mississippi.,Department of Radiology, University of Mississippi Medical Center , Jackson, Mississippi
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18
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Cai W, Li Y, Liu F, Luo J. Quantitative evaluation of graded hindlimb ischemia based on pharmacokinetic modelling and hemodynamic analysis of indocyanine green. Physiol Meas 2018; 39:015009. [PMID: 29231185 DOI: 10.1088/1361-6579/aaa108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Accurate evaluation of the degree of hindlimb ischemia is challenging but essential for the diagnosis and treatment of peripheral vascular insufficiency. The aim of the study is to apply a multiparametric method for the quantitative estimation of mouse models with different degrees of hindlimb ischemia based on a dynamic fluorescence imaging-based strategy. APPROACH An adjustable hydraulic occluder was placed around the thigh root of one hindlimb to induce six different degrees of hindlimb ischemia. Five parameters were extracted to quantitatively evaluate the degree of ischemia, including perfusion rate (PR) and perfusion vascular density (PVD) from a mathematical model of indocyanine green (ICG) pharmacokinetics, rising time (T rise), blood flow index (BFI) and mean fluorescence intensity (MFI) from time-series analysis of ICG hemodynamics. MAIN RESULTS The results showed that the normalized PR and BFI decreased while the normalized T rise increased progressively with the degree of ischemia. The normalized PVD and MFI first increased and then decreased with the degree of ischemia. High correlation was observed between the degree of ischemia and the arterial oxygen saturation which was measured by an oximeter. SIGNIFICANCE The results of this work demonstrated that PR, BFI and T rise can be used for the quantitative and comprehensive evaluation of graded hindlimb ischemia.
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Affiliation(s)
- Wenjuan Cai
- Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, People's Republic of China
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19
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Eirin A, Woollard JR, Ferguson CM, Jordan KL, Tang H, Textor SC, Lerman A, Lerman LO. The metabolic syndrome induces early changes in the swine renal medullary mitochondria. Transl Res 2017; 184:45-56.e9. [PMID: 28363084 PMCID: PMC5429873 DOI: 10.1016/j.trsl.2017.03.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 02/20/2017] [Accepted: 03/03/2017] [Indexed: 12/31/2022]
Abstract
The metabolic syndrome (MetS) is associated with nutrient surplus and kidney hyperfiltration, accelerating chronic renal failure. Mitochondria can be overwhelmed by substrate excess, leading to inefficient energy production and thereby tissue hypoxia. Mitochondrial dysfunction is emerging as an important determinant of renal damage, but whether it contributes to MetS-induced renal injury remains unknown. We hypothesized that early MetS induces kidney mitochondrial abnormalities and dysfunction, which would be notable in the vulnerable renal medulla. Pigs were studied after 16 weeks of diet-induced MetS, MetS treated for the last 4 weeks with the mitochondria-targeted peptide elamipretide (0.1 mg/kg SC q.d), and Lean controls (n = 7 each). Single-kidney renal blood flow, glomerular filtration rate, and oxygenation were measured in-vivo, whereas cortical and medullary mitochondrial structure and function and renal injurious pathways were studied ex-vivo. Blood pressure was slightly elevated in MetS pigs, and their renal blood flow and glomerular filtration rate were elevated. Blood oxygen level-dependent magnetic resonance imaging demonstrated that this was associated with medullary hypoxia, whereas cortical oxygenation remained intact. MetS decreased renal content of the inner mitochondrial membrane cardiolipin, particularly the tetra-linoleoyl (C18:2) cardiolipin species, and altered mitochondrial morphology and function, particularly in the medullary thick ascending limb. MetS also increased renal cytochrome-c-induced apoptosis, oxidative stress, and tubular injury. Chronic mitoprotection restored mitochondrial structure, ATP synthesis, and antioxidant defenses and decreased mitochondrial oxidative stress, medullary hypoxia, and renal injury. These findings implicate medullary mitochondrial damage in renal injury in experimental MetS, and position the mitochondria as a therapeutic target.
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Affiliation(s)
- Alfonso Eirin
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minn
| | - John R Woollard
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minn
| | | | - Kyra L Jordan
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minn
| | - Hui Tang
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minn
| | - Stephen C Textor
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minn
| | - Amir Lerman
- Cardiovascular Diseases, Mayo Clinic, Rochester, Minn
| | - Lilach O Lerman
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minn; Cardiovascular Diseases, Mayo Clinic, Rochester, Minn.
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20
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Abstract
BACKGROUND We hypothesized that nicotinamide adenosine diphosphate oxidase 2 (Nox2) plays an important role in cyclosporine A (CsA)-induced chronic hypoxia. METHODS We tested this hypothesis in Fisher 344 rats, C57BL/6 J wild type and Nox2-/- mice, and in liver transplant recipients with chronic CsA nephrotoxicity. We used noninvasive molecular imaging (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging) and molecular diagnostic tools to assess intrarenal oxygenation and perfusion, and the molecular phenotype of CsA nephrotoxicity. RESULTS We observed that chemical and genetic inhibition of Nox2 in rats and mice resulted in the prevention of CsA-induced hypoxia independent of regional perfusion (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging, pimonidazole, HIF-1α). Nicotinamide adenosine diphosphate oxidase 2 knockout was also associated with decreased oxidative stress (Nox2, HIF-1α, hydrogen peroxide, hydroxynonenal), and fibrogenesis (α-smooth muscle actin, picrosirius red, trichrome, vimentin). The molecular signature of chronic CsA nephrotoxicity using transcriptomic analyses demonstrated significant changes in 40 genes involved in injury repair, metabolism, and oxidative stress in Nox2-/- mice. Immunohistochemical analyses of kidney biopsies from liver transplant recipients with chronic CsA nephrotoxicity showed significantly greater Nox2, α-smooth muscle actin and picrosirius levels compared with controls. CONCLUSIONS These studies suggest that Nox2 is a modulator of CsA-induced hypoxia upstream of HIF-1α and define the molecular characteristics that could be used for the diagnosis and monitoring of chronic calcineurin inhibitor nephrotoxicity.
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21
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Karanikola E, Karaolanis G, Galyfos G, Barbaressos E, Palla V, Filis K. Endovascular Management of Atherosclerotic Renal Artery Stenosis: Post-Cardiovascular Outcomes in Renal Atherosclerotic Lesions Era Winner or False Alarm? Vasc Specialist Int 2017; 33:1-15. [PMID: 28377906 PMCID: PMC5374954 DOI: 10.5758/vsi.2017.33.1.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 01/10/2017] [Accepted: 01/10/2017] [Indexed: 12/25/2022] Open
Abstract
Renal artery stenosis (RAS) is frequently associated with severe comorbidities such as reduced renal perfusion, hypertension, and end-stage renal failure. In approximately 90% of patients, renal artery atherosclerosis is the main cause for RAS, and it is associated with an increased risk for fatal and non-fatal cardiovascular and renal complications. Endovascular management of atherosclerotic RAS (ARAS) has been recently evaluated by several randomized controlled trials that failed to demonstrate benefit of stenting. Furthermore, the Cardiovascular Outcomes in Renal Atherosclerotic Lesions study did not demonstrate any benefit over the revascularization approach. In this review, we summarized the available data from retrospective, prospective and randomized trials on ARAS to provide clinicians with sufficient data in order to produce useful conclusions for everyday clinical practice.
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Affiliation(s)
- Evridiki Karanikola
- Division of Vascular Surgery, 1st Department of Propaedeutic Surgery, University of Athens Medical School, Hippocration General Hospital, Athens, Greece
| | - Georgios Karaolanis
- Vascular Surgery Unit, 1st Department of Surgery, University of Athens Medical School, Laikon General Hospital, Athens, Greece
| | - George Galyfos
- Division of Vascular Surgery, 1st Department of Propaedeutic Surgery, University of Athens Medical School, Hippocration General Hospital, Athens, Greece
| | - Emmanuel Barbaressos
- Division of Vascular Surgery, 1st Department of Propaedeutic Surgery, University of Athens Medical School, Hippocration General Hospital, Athens, Greece
| | - Viktoria Palla
- Vascular Surgery Unit, 1st Department of Surgery, University of Athens Medical School, Laikon General Hospital, Athens, Greece
| | - Konstantinos Filis
- Division of Vascular Surgery, 1st Department of Propaedeutic Surgery, University of Athens Medical School, Hippocration General Hospital, Athens, Greece
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22
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Pruijm M, Milani B, Burnier M. Blood Oxygenation Level-Dependent MRI to Assess Renal Oxygenation in Renal Diseases: Progresses and Challenges. Front Physiol 2017; 7:667. [PMID: 28105019 PMCID: PMC5214762 DOI: 10.3389/fphys.2016.00667] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 12/19/2016] [Indexed: 11/13/2022] Open
Abstract
BOLD-MRI (blood oxygenation-level dependent magnetic resonance imaging) allows non-invasive measurement of renal tissue oxygenation in humans, without the need for contrast products. BOLD-MRI uses the fact that magnetic properties of hemoglobin depend of its oxygenated state:: the higher local deoxyhemoglobin, the higher the so called apparent relaxation rate R2* (sec-1), and the lower local tissue oxygen content. Several factors other than deoxyhemoglobin (such as hydration status, dietary sodium intake, and susceptibility effects) influence the BOLD signal, and need to be taken into account when interpreting results. The last 5 years have witnessed important improvements in the standardization of these factors, and the appearance of new, highly reproducible analysis techniques of BOLD-images, that are reviewed in this article. Using these new BOLD-MRI analysis techniques, it has recently been shown that persons suffering from chronic kidney diseases (CKD) have lower cortical oxygenation than normotensive controls, thus confirming the chronic hypoxia hypothesis. The acute alterations in R2* after the administration of furosemide are smaller in CKD, and represent an estimate of the oxygen-dependent tubular transport of sodium. BOLD-MRI-alone or in combination with other functional MRI methods- can be used to monitor the renal effects of drugs, and is increasingly used in the preclinical setting. The near future will tell whether or not BOLD-MRI represents a new tool to predict renal function decline an adverse renal outcome.
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Affiliation(s)
- Menno Pruijm
- Service of Nephrology and Hypertension, Department of Medicine, Centre Hospitalier Universitaire Vaudois Lausanne, Switzerland
| | - Bastien Milani
- Service of Nephrology and Hypertension, Department of Medicine, Centre Hospitalier Universitaire Vaudois Lausanne, Switzerland
| | - Michel Burnier
- Service of Nephrology and Hypertension, Department of Medicine, Centre Hospitalier Universitaire Vaudois Lausanne, Switzerland
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23
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Deux JF, Audard V, Brugières P, Habibi A, Manea EM, Guillaud-Danis C, Godeau B, Galactéros F, Stehlé T, Lang P, Grimbert P, Audureau E, Rahmouni A, Bartolucci P. Magnetic Resonance Imaging Assessment of Kidney Oxygenation and Perfusion During Sickle Cell Vaso-occlusive Crises. Am J Kidney Dis 2017; 69:51-59. [DOI: 10.1053/j.ajkd.2016.07.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 07/18/2016] [Indexed: 12/25/2022]
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24
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Fournier T, Sens F, Rouvière O, Millon A, Juillard L. [Management of atherosclerotic renal-artery stenosis in 2016]. Nephrol Ther 2016; 13:1-8. [PMID: 27887845 DOI: 10.1016/j.nephro.2016.07.450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 07/09/2016] [Accepted: 07/11/2016] [Indexed: 11/26/2022]
Abstract
Endovascular revascularization as treatment of atherosclerotic renal-artery stenosis (aRAS) is controversial since 3 large and multicentric randomised trials (CORAL, ASTRAL, STAR) failed to prove the superiority of percutaneous transluminal renal-artery stenting (PTRAS) over medical treatment only (MT). However, considering the multiple bias of these trials, among which questionable inclusion criterias, these results must be extrapolated in clinical practice with caution. New pathophysiological data have been helping to understand why restoring blood flow does not necessarily lead to kidney function improvement. Today, the diagnostic approach must in one hand confirm the artery stenosis and on the other hand assess its severity and impact on the kidney. Therapeutic options still lie on the American guidelines published in 2006, since no study data can be reasonably used in everyday practice. However, particular sub-groups of patients who could benefit from revascularisation have been identified through recent cohort studies. Further prospective studies are needed in order to confirm the superiority of PTRAS in these populations. Meanwhile, multidisciplinary approach should be promoted, in order to provide the best treatment for each patient.
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Affiliation(s)
- Thomas Fournier
- Service de néphrologie, hôpital Édouard-Herriot, hospices civils de Lyon, 5, place d'Arsonval, 69003 Lyon, France; Université Lyon 1, 43, boulevard du 11-novembre-1918, 69622 Villeurbanne cedex, France.
| | - Florence Sens
- Service de néphrologie, hôpital Édouard-Herriot, hospices civils de Lyon, 5, place d'Arsonval, 69003 Lyon, France; Université Lyon 1, 43, boulevard du 11-novembre-1918, 69622 Villeurbanne cedex, France; Pôle IMER, site Lacassagne, hospices civils de Lyon, 5, place d'Arsonval, 69003 Lyon, France
| | - Olivier Rouvière
- Université Lyon 1, 43, boulevard du 11-novembre-1918, 69622 Villeurbanne cedex, France; Service d'imagerie vasculaire et urinaire, hôpital Édouard-Herriot, hospices civils de Lyon, 5, place d'Arsonval, 69003 Lyon, France
| | - Antoine Millon
- Université Lyon 1, 43, boulevard du 11-novembre-1918, 69622 Villeurbanne cedex, France; Service de chirurgie vasculaire, hôpital Édouard-Herriot, hospices civils de Lyon, 5, place d'Arsonval, 69003 Lyon, France
| | - Laurent Juillard
- Service de néphrologie, hôpital Édouard-Herriot, hospices civils de Lyon, 5, place d'Arsonval, 69003 Lyon, France; Université Lyon 1, 43, boulevard du 11-novembre-1918, 69622 Villeurbanne cedex, France; OPeRa, Carmen, université Lyon 1, 11, avenue Jean-Capelle, 69621 Villeurbanne cedex, France
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25
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Wang C, Zhao K, Zhang R, Jiang L, Wang R, Zhang X, Wang H, Jin L, Zhang J, Wang X, Fang J. Evaluation of renal oxygenation change under the influence of carbogen breathing using a dynamic R 2 , R 2 ' and R 2 * quantification approach. NMR IN BIOMEDICINE 2016; 29:1601-1607. [PMID: 27670144 DOI: 10.1002/nbm.3625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 08/03/2016] [Accepted: 08/22/2016] [Indexed: 06/06/2023]
Abstract
The purpose of this study is to demonstrate the feasibility of dynamic renal R2 /R2 '/R2 * measurements based on a method, denoted psMASE-ME, in which a periodic 180° pulse-shifting multi-echo asymmetric spin echo (psMASE) sequence, combined with a moving estimation (ME) strategy, is adopted. Following approval by the institutional animal care and use committee, a block design of respiratory challenge with interleaved air and carbogen (97% O2 , 3% CO2 ) breathing was employed in nine rabbits. Parametrical R2 /R2 '/R2 * maps were computed and average R2 /R2 '/R2 * values were measured in regions of interest in the renal medulla and cortex. Bland-Altman plots showed good agreement between the proposed method and reference standards of multi-echo spin echo and multi-echo gradient echo sequences. Renal R2 , R2 ' and R2 * decreased significantly from 16.2 ± 4.4 s-1 , 9.8 ± 5.2 s-1 and 25.9 ± 5.0 s-1 to 14.9 ± 4.4 s-1 (p < 0.05), 8.5 ± 4.1 s-1 (p < 0.05) and 23.4 ± 4.8 s-1 (p < 0.05) in the cortex when switching the gas mixture from room air to carbogen. In the renal medulla, R2 , R2 ' and R2 * also decreased significantly from 12.9 ± 4.7 s-1 , 15.1 ± 5.8 s-1 and 27.9 ± 5.3 s-1 to 11.8 ± 4.5 s-1 (p < 0.05), 14.2 ± 4.2 s-1 (p < 0.05) and 25.8 ± 5.1 s-1 (p < 0.05). No statistically significant differences in relative R2 , R2 ' and R2 * changes were observed between the cortex and medulla (p = 0.72 for R2 , p = 0.39 for R2 ' and p = 0.61 for R2 *). The psMASE-ME method for dynamic renal R2 /R2 '/R2 * measurements, together with the respiratory challenge, has potential use in the evaluation of renal oxygenation in many renal diseases.
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Affiliation(s)
- Chengyan Wang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Kai Zhao
- Department of Radiology, Peking University First Hospital, Beijing, China
| | - Rui Zhang
- College of Engineering, Peking University, Beijing, China
| | - Li Jiang
- Philips Healthcare, Suzhou, Jiangsu, China
| | - Rui Wang
- Department of Radiology, Peking University First Hospital, Beijing, China
| | - Xiaodong Zhang
- Department of Radiology, Peking University First Hospital, Beijing, China
| | - He Wang
- Philips Healthcare, Suzhou, Jiangsu, China
| | - Lixin Jin
- Philips Healthcare, Suzhou, Jiangsu, China
| | - Jue Zhang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
- College of Engineering, Peking University, Beijing, China.
| | - Xiaoying Wang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
- Department of Radiology, Peking University First Hospital, Beijing, China.
| | - Jing Fang
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- College of Engineering, Peking University, Beijing, China
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Saad A, Herrmann SM, Textor SC. Chronic renal ischemia in humans: can cell therapy repair the kidney in occlusive renovascular disease? Physiology (Bethesda) 2016; 30:175-82. [PMID: 25933818 DOI: 10.1152/physiol.00065.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Occlusive renovascular disease caused by atherosclerotic renal artery stenosis (ARAS) elicits complex biological responses that eventually lead to loss of kidney function. Recent studies indicate a complex interplay of oxidative stress, endothelial dysfunction, and activation of fibrogenic and inflammatory cytokines as a result of atherosclerosis, hypoxia, and renal hypoperfusion in this disorder. Human studies emphasize the limits of the kidney adaptation to reduced blood flow, eventually leading to renal hypoxia with activation of inflammatory and fibrogenic pathways. Several randomized prospective clinical trials show that stent revascularization alone in patients with atherosclerotic renal artery stenosis provides little additional benefit to medical therapy once these processes have developed and solidified. Experimental data now support developing adjunctive cell-based measures to support angiogenesis and anti-inflammatory renal repair mechanisms. These data encourage the study of endothelial progenitor cells and/or mesenchymal stem/stromal cells for the repair of damaged kidney tissue.
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Affiliation(s)
- Ahmed Saad
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Sandra M Herrmann
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Stephen C Textor
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
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27
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Zhou HY, Chen TW, Zhang XM. Functional Magnetic Resonance Imaging in Acute Kidney Injury: Present Status. BIOMED RESEARCH INTERNATIONAL 2016; 2016:2027370. [PMID: 26925411 PMCID: PMC4746277 DOI: 10.1155/2016/2027370] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 01/05/2016] [Accepted: 01/06/2016] [Indexed: 12/27/2022]
Abstract
Acute kidney injury (AKI) is a common complication of hospitalization that is characterized by a sudden loss of renal excretory function and associated with the subsequent development of chronic kidney disease, poor prognosis, and increased mortality. Although the pathophysiology of renal functional impairment in the setting of AKI remains poorly understood, previous studies have identified changes in renal hemodynamics, perfusion, and oxygenation as key factors in the development and progression of AKI. The early assessment of these changes remains a challenge. Many established approaches are not applicable to humans because of their invasiveness. Functional renal magnetic resonance (MR) imaging offers an alternative assessment tool that could be used to evaluate renal morphology and function noninvasively and simultaneously. Thus, the purpose of this review is to illustrate the principle, application, and role of the techniques of functional renal MR imaging, including blood oxygen level-dependent imaging, arterial spin labeling, and diffusion-weighted MR imaging, in the management of AKI. The use of gadolinium in MR imaging may exacerbate renal impairment and cause nephrogenic systemic fibrosis. Therefore, dynamic contrast-enhanced MR imaging will not be discussed in this paper.
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Affiliation(s)
- Hai Ying Zhou
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, 63 Wenhua Road, Shunqing District, Nanchong, Sichuan 637000, China
| | - Tian Wu Chen
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, 63 Wenhua Road, Shunqing District, Nanchong, Sichuan 637000, China
| | - Xiao Ming Zhang
- Sichuan Key Laboratory of Medical Imaging, Department of Radiology, Affiliated Hospital of North Sichuan Medical College, 63 Wenhua Road, Shunqing District, Nanchong, Sichuan 637000, China
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28
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Wang C, Zhang R, Wang R, Jiang L, Zhang X, Wang H, Zhao K, Jin L, Zhang J, Wang X, Fang J. Noninvasive measurement of renal oxygen extraction fraction under the influence of respiratory challenge. J Magn Reson Imaging 2016; 44:230-7. [PMID: 26800848 DOI: 10.1002/jmri.25163] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/04/2016] [Indexed: 12/12/2022] Open
Affiliation(s)
- Chengyan Wang
- Academy for Advanced Interdisciplinary Studies; Peking University; Beijing PR China
| | - Rui Zhang
- College of Engineering; Peking University; Beijing PR China
| | - Rui Wang
- Department of Radiology; Peking University First Hospital; Beijing PR China
| | - Li Jiang
- Philips Healthcare; Suzhou Jiangsu PR China
| | - Xiaodong Zhang
- Department of Radiology; Peking University First Hospital; Beijing PR China
| | - He Wang
- Philips Healthcare; Suzhou Jiangsu PR China
| | - Kai Zhao
- Department of Radiology; Peking University First Hospital; Beijing PR China
| | - Lixin Jin
- Philips Healthcare; Suzhou Jiangsu PR China
| | - Jue Zhang
- Academy for Advanced Interdisciplinary Studies; Peking University; Beijing PR China
- College of Engineering; Peking University; Beijing PR China
| | - Xiaoying Wang
- Academy for Advanced Interdisciplinary Studies; Peking University; Beijing PR China
- Department of Radiology; Peking University First Hospital; Beijing PR China
| | - Jing Fang
- Academy for Advanced Interdisciplinary Studies; Peking University; Beijing PR China
- College of Engineering; Peking University; Beijing PR China
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Humphreys BD, Cantaluppi V, Portilla D, Singbartl K, Yang L, Rosner MH, Kellum JA, Ronco C. Targeting Endogenous Repair Pathways after AKI. J Am Soc Nephrol 2015; 27:990-8. [PMID: 26582401 DOI: 10.1681/asn.2015030286] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
AKI remains a highly prevalent disease associated with poor short- and long-term outcomes and high costs. Although significant advances in our understanding of repair after AKI have been made over the last 5 years, this knowledge has not yet been translated into new AKI therapies. A consensus conference held by the Acute Dialysis Quality Initiative was convened in April of 2014 and reviewed new evidence on successful kidney repair to identify the most promising pathways that could be translated into new treatments. In this paper, we provide a summary of current knowledge regarding successful kidney repair and offer a framework for conceptualizing the therapeutic targeting that may facilitate this process. We outline gaps in knowledge and suggest a research agenda to more efficiently bring new discoveries regarding repair after AKI to the clinic.
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Affiliation(s)
- Benjamin D Humphreys
- Renal Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri;
| | - Vincenzo Cantaluppi
- Nephrology, Dialysis and Kidney Transplantation Unit, Department of Medical Sciences, University of Torino, Azienda Ospedaliera Città della Salute e della Scienza 'Molinette,' Turin, Italy
| | - Didier Portilla
- Division of Nephrology, Center for Immunity, Inflammation and Regenerative Medicine, University of Virginia Health System, Charlottesville, Virginia
| | - Kai Singbartl
- Center for Critical Care Nephrology and Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Li Yang
- Renal Division, Peking University First Hospital, Beijing, China; and
| | - Mitchell H Rosner
- Division of Nephrology, Center for Immunity, Inflammation and Regenerative Medicine, University of Virginia Health System, Charlottesville, Virginia
| | - John A Kellum
- Center for Critical Care Nephrology and Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Claudio Ronco
- Department of Nephrology Dialysis and Transplantation, San Bortolo Hospital and the International Renal Research Institute, Vicenza, Italy
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30
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Wang YT, Li YC, Yin LL, Pu H, Chen JY. Functional assessment of transplanted kidneys with magnetic resonance imaging. World J Radiol 2015; 7:343-349. [PMID: 26516431 PMCID: PMC4620115 DOI: 10.4329/wjr.v7.i10.343] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/17/2015] [Accepted: 09/08/2015] [Indexed: 02/06/2023] Open
Abstract
Kidney transplantation has emerged as the treatment of choice for many patients with end-stage renal disease, which is a significant cause of morbidity and mortality. Given the shortage of clinically available donor kidneys and the significant incidence of allograft dysfunction, a noninvasive and accurate assessment of the allograft renal function is critical for postoperative management. Prompt diagnosis of graft dysfunction facilitates clinical intervention of kidneys with salvageable function. New advances in magnetic resonance imaging (MRI) technology have enabled the calculation of various renal parameters that were previously not feasible to measure noninvasively. Diffusion-weighted imaging provides information on renal diffusion and perfusion simultaneously, with quantification by the apparent diffusion coefficient, the decrease of which reflects renal function impairment. Diffusion-tensor imaging accounts for the directionality of molecular motion and measures fractional anisotropy of the kidneys. Blood oxygen level-dependent MR evaluates intrarenal oxygen bioavailability, generating the parameter of R2* (reflecting the concentration of deoxyhemoglobin). A decrease in R2* could happen during acute rejection. MR nephro-urography/renography demonstrates structural data depicting urinary tract obstructions and functional data regarding the glomerular filtration and blood flow. MR angiography details the transplant vasculature and is particularly suitable for detecting vascular complications, with good correlation with digital subtraction angiography. Other functional MRI technologies, such as arterial spin labeling and MR spectroscopy, are showing additional promise. This review highlights MRI as a comprehensive modality to diagnose a variety of etiologies of graft dysfunction, including prerenal (e.g., renal vasculature), renal (intrinsic causes) and postrenal (e.g., obstruction of the collecting system) etiologies.
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31
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Xie L, Layton AT, Wang N, Larson PEZ, Zhang JL, Lee VS, Liu C, Johnson GA. Dynamic contrast-enhanced quantitative susceptibility mapping with ultrashort echo time MRI for evaluating renal function. Am J Physiol Renal Physiol 2015; 310:F174-82. [PMID: 26447222 DOI: 10.1152/ajprenal.00351.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 10/06/2015] [Indexed: 12/30/2022] Open
Abstract
Dynamic contrast-enhanced (DCE) MRI can provide key insight into renal function. DCE MRI is typically achieved through an injection of a gadolinium (Gd)-based contrast agent, which has desirable T1 quenching and tracer kinetics. However, significant T2* blooming effects and signal voids can arise when Gd becomes very concentrated, especially in the renal medulla and pelvis. One MRI sequence designed to alleviate T2* effects is the ultrashort echo time (UTE) sequence. In the present study, we observed T2* blooming in the inner medulla of the mouse kidney, despite using UTE at an echo time of 20 microseconds and a low dose of 0.03 mmol/kg Gd. We applied quantitative susceptibility mapping (QSM) and resolved the signal void into a positive susceptibility signal. The susceptibility values [in parts per million (ppm)] were converted into molar concentrations of Gd using a calibration curve. We determined the concentrating mechanism (referred to as the concentrating index) as a ratio of maximum Gd concentration in the inner medulla to the renal artery. The concentrating index was assessed longitudinally over a 17-wk course (3, 5, 7, 9, 13, 17 wk of age). We conclude that the UTE-based DCE method is limited in resolving extreme T2* content caused by the kidney's strong concentrating mechanism. QSM was able to resolve and confirm the source of the blooming effect to be the large positive susceptibility of concentrated Gd. UTE with QSM can complement traditional magnitude UTE and offer a powerful tool to study renal pathophysiology.
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Affiliation(s)
- Luke Xie
- Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Durham, North Carolina; Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, Utah
| | - Anita T Layton
- Department of Mathematics, Duke University, Durham, North Carolina
| | - Nian Wang
- Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina
| | - Peder E Z Larson
- Department of Radiology and Biomedical Engineering, University of California, San Francisco, California; and
| | - Jeff L Zhang
- Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, Utah
| | - Vivian S Lee
- Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, Salt Lake City, Utah
| | - Chunlei Liu
- Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Durham, North Carolina; Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina
| | - G Allan Johnson
- Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Durham, North Carolina
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Zhang R, Wang Y, Chen F, Wang Q, Wang Z, Chen Y, Xiao W. Noninvasive evaluation of renal oxygenation in primary nephrotic syndrome with blood oxygen level dependent magnetic resonance imaging: Initial experience. J Int Med Res 2015; 43:356-63. [PMID: 25947644 DOI: 10.1177/0300060515579117] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 03/05/2015] [Indexed: 01/30/2023] Open
Abstract
OBJECTIVES To use blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) to evaluate renal oxygenation in patients with primary nephrotic syndrome (PNS), and test the hypothesis that renal tissue oxygenation correlates with renal function, tubulointerstitial alterations and treatment response. METHODS Patients with untreated first-onset PNS and healthy control subjects underwent BOLD MRI. Blood and urine samples were obtained on the day of MRI, and patients underwent renal biopsy the day after MRI. Renal tubulointerstitial damage scores (TIDS) were determined using Katafuchi criteria. All patients received corticosteroids within 7 days after MRI and were followed up for 12 months. RESULTS Medullary R2* values were significantly lower in patients with PNS (n = 20) than controls (n = 18). Medullary R2* values were negatively correlated with estimated glomerular filtration rates and positively correlated with TIDS in patients with PNS. There were no significant differences in medullary or cortical R2* values when patients were classified according to treatment response. CONCLUSIONS The medullary oxygen concentration was higher in patients with PNS than in control subjects. BOLD MRI was a useful noninvasive method for the evaluation of renal function and tubulointerstitial impairment.
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Affiliation(s)
- Rui Zhang
- Department of Radiology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yao Wang
- Department of Ultrasonography, The Second Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Feng Chen
- Department of Radiology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Qidong Wang
- Department of Radiology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Zhaoming Wang
- Department of Pathology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yilun Chen
- Kidney Disease Centre, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Wenbo Xiao
- Department of Radiology, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
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Detailing the relation between renal T2* and renal tissue pO2 using an integrated approach of parametric magnetic resonance imaging and invasive physiological measurements. Invest Radiol 2015; 49:547-60. [PMID: 24651661 DOI: 10.1097/rli.0000000000000054] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES This study was designed to detail the relation between renal T2* and renal tissue pO2 using an integrated approach that combines parametric magnetic resonance imaging (MRI) and quantitative physiological measurements (MR-PHYSIOL). MATERIALS AND METHODS Experiments were performed in 21 male Wistar rats. In vivo modulation of renal hemodynamics and oxygenation was achieved by brief periods of aortic occlusion, hypoxia, and hyperoxia. Renal perfusion pressure (RPP), renal blood flow (RBF), local cortical and medullary tissue pO2, and blood flux were simultaneously recorded together with T2*, T2 mapping, and magnetic resonance-based kidney size measurements (MR-PHYSIOL). Magnetic resonance imaging was carried out on a 9.4-T small-animal magnetic resonance system. Relative changes in the invasive quantitative parameters were correlated with relative changes in the parameters derived from MRI using Spearman analysis and Pearson analysis. RESULTS Changes in T2* qualitatively reflected tissue pO2 changes induced by the interventions. T2* versus pO2 Spearman rank correlations were significant for all interventions, yet quantitative translation of T2*/pO2 correlations obtained for one intervention to another intervention proved not appropriate. The closest T2*/pO2 correlation was found for hypoxia and recovery. The interlayer comparison revealed closest T2*/pO2 correlations for the outer medulla and showed that extrapolation of results obtained for one renal layer to other renal layers must be made with due caution. For T2* to RBF relation, significant Spearman correlations were deduced for all renal layers and for all interventions. T2*/RBF correlations for the cortex and outer medulla were even superior to those between T2* and tissue pO2. The closest T2*/RBF correlation occurred during hypoxia and recovery. Close correlations were observed between T2* and kidney size during hypoxia and recovery and for occlusion and recovery. In both cases, kidney size correlated well with renal vascular conductance, as did renal vascular conductance with T2*. Our findings indicate that changes in T2* qualitatively mirror changes in renal tissue pO2 but are also associated with confounding factors including vascular volume fraction and tubular volume fraction. CONCLUSIONS Our results demonstrate that MR-PHYSIOL is instrumental to detail the link between renal tissue pO2 and T2* in vivo. Unravelling the link between regional renal T2* and tissue pO2, including the role of the T2* confounding parameters vascular and tubular volume fraction and oxy-hemoglobin dissociation curve, requires further research. These explorations are essential before the quantitative capabilities of parametric MRI can be translated from experimental research to improved clinical understanding of hemodynamics/oxygenation in kidney disorders.
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Niendorf T, Pohlmann A, Arakelyan K, Flemming B, Cantow K, Hentschel J, Grosenick D, Ladwig M, Reimann H, Klix S, Waiczies S, Seeliger E. How bold is blood oxygenation level-dependent (BOLD) magnetic resonance imaging of the kidney? Opportunities, challenges and future directions. Acta Physiol (Oxf) 2015; 213:19-38. [PMID: 25204811 DOI: 10.1111/apha.12393] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/04/2014] [Accepted: 09/04/2014] [Indexed: 12/11/2022]
Abstract
Renal tissue hypoperfusion and hypoxia are key elements in the pathophysiology of acute kidney injury and its progression to chronic kidney disease. Yet, in vivo assessment of renal haemodynamics and tissue oxygenation remains a challenge. Many of the established approaches are invasive, hence not applicable in humans. Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) offers an alternative. BOLD-MRI is non-invasive and indicative of renal tissue oxygenation. Nonetheless, recent (pre-) clinical studies revived the question as to how bold renal BOLD-MRI really is. This review aimed to deliver some answers. It is designed to inspire the renal physiology, nephrology and imaging communities to foster explorations into the assessment of renal oxygenation and haemodynamics by exploiting the powers of MRI. For this purpose, the specifics of renal oxygenation and perfusion are outlined. The fundamentals of BOLD-MRI are summarized. The link between tissue oxygenation and the oxygenation-sensitive MR biomarker T2∗ is outlined. The merits and limitations of renal BOLD-MRI in animal and human studies are surveyed together with their clinical implications. Explorations into detailing the relation between renal T2∗ and renal tissue partial pressure of oxygen (pO2 ) are discussed with a focus on factors confounding the T2∗ vs. tissue pO2 relation. Multi-modality in vivo approaches suitable for detailing the role of the confounding factors that govern T2∗ are considered. A schematic approach describing the link between renal perfusion, oxygenation, tissue compartments and renal T2∗ is proposed. Future directions of MRI assessment of renal oxygenation and perfusion are explored.
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Affiliation(s)
- T. Niendorf
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - A. Pohlmann
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - K. Arakelyan
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - B. Flemming
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - K. Cantow
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - J. Hentschel
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - D. Grosenick
- Physikalisch-Technische Bundesanstalt (PTB); Berlin Germany
| | - M. Ladwig
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
| | - H. Reimann
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - S. Klix
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - S. Waiczies
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin Germany
| | - E. Seeliger
- Institute of Physiology and Center for Cardiovascular Research (CCR); Charité - Universitätsmedizin Berlin; Berlin Germany
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Zheng Z, Shi H, Ma H, Li F, Zhang J, Zhang Y. Renal Oxygenation Characteristics in Healthy Native Kidneys: Assessment with Blood Oxygen Level-Dependent Magnetic Resonance Imaging. Nephron Clin Pract 2014; 128:47-54. [PMID: 25471091 DOI: 10.1159/000366448] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 08/04/2014] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE To explore the characteristics of blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) in healthy native kidneys. METHODS Seventy-nine patients without chronic kidney disease underwent BOLD-MRI with T2* spoiled gradient recalled echo sequences. BOLD images were analyzed using R2*map software to produce an R2* pseudo-color map. Cortical and medullary R2* values were analyzed in both kidneys and in both sexes. Different regional R2* values in the cortex and medulla were also analyzed. Physiological indices including age, height, weight, body mass index, body surface area, and estimated glomerular filtration rate (eGFR) were recorded. Correlations between R2* value and physiological indices were determined. RESULTS Renal cortical R2* values were lower than values in the medulla (p < 0.001). Female and male cortical R2* values were also lower than the corresponding values in the medulla (p < 0.001). Renal medullary R2* values in the lower renal pole were lower than values in the middle and upper poles (p = 0.001). Age was positively correlated with R2* values in the medulla (r = 0.32, p = 0.004). eGFR was negatively correlated with both cortical R2* values (r = -0.26, p = 0.02) and medullary R2* values (r = -0.29, p = 0.009). CONCLUSIONS BOLD-MRI can directly visualize renal oxygenation. There was variation in the oxygenation of different regions of the kidney. Renal cortical and medullary oxygenation in healthy kidneys decreased with patient age. eGFR also decreased with patient age.
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Affiliation(s)
- Zhenfeng Zheng
- Department of Nephrology, General Hospital of Tianjin Medical University, Tianjin, PR China
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Neugarten J, Golestaneh L. Blood oxygenation level-dependent MRI for assessment of renal oxygenation. Int J Nephrol Renovasc Dis 2014; 7:421-35. [PMID: 25473304 PMCID: PMC4247132 DOI: 10.2147/ijnrd.s42924] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently emerged as an important noninvasive technique to assess intrarenal oxygenation under physiologic and pathophysiologic conditions. Although this tool represents a major addition to our armamentarium of methodologies to investigate the role of hypoxia in the pathogenesis of acute kidney injury and progressive chronic kidney disease, numerous technical limitations confound interpretation of data derived from this approach. BOLD MRI has been utilized to assess intrarenal oxygenation in numerous experimental models of kidney disease and in human subjects with diabetic and nondiabetic chronic kidney disease, acute kidney injury, renal allograft rejection, contrast-associated nephropathy, and obstructive uropathy. However, confidence in conclusions based on data derived from BOLD MRI measurements will require continuing advances and technical refinements in the use of this technique.
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Affiliation(s)
- Joel Neugarten
- Renal Division, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Ladan Golestaneh
- Renal Division, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY, USA
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Prigent A, Chaumet-Riffaud P. Clinical problems in renovascular disease and the role of nuclear medicine. Semin Nucl Med 2014; 44:110-22. [PMID: 24484748 DOI: 10.1053/j.semnuclmed.2013.10.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Although renovascular disease remains defined as a stenosis of the main renal artery or its proximal branches (renal artery stenosis [RAS]), its clinical overview has changed dramatically over the last 15-20 years and its management is more controversial than ever before. The clinical problems, not only diagnosis and treatment but also the relative contribution of different pathophysiological mechanisms involved in the progression of kidney disease, have shifted dramatically. This presentation aims to emphasize the paradigm change revisiting the (recent) past focused on renovascular hypertension (RVH) to the current context of preservation or recovery of threatened renal function in patients with progressive atherosclerotic renovascular disease until its last stage of irreversible "ischemic nephropathy." In the past, the foreground was occupied by RVH, a very rare disease, where the activation of the renin-angiotensin-aldosterone system (RAAS) was supposed to play the major, if not only, role in RVH issues. The retrospective RVH diagnosis was established either on the improvement or, more rarely, on the cure of hypertension after revascularization by, most often, a percutaneous transluminal renal angioplasty with or without a stent placement. At this time, captoptril radionuclide renography was an efficient diagnostic tool, because it was a functional (angiotensin-converting enzyme inhibition), noninvasive test aiming to evidence both the RAAS activation and the lateralization (or asymmetry) of renin secretion by the kidney affected by a "hemodynamically significant" RAS. At present, even if captoptril radionuclide renography could be looked upon as the most efficient (and cost effective in selected high-risk patients) noninvasive, functional test to predict the improvement of hypertension after RAS correction, its clinical usefulness is questioned as the randomized, prospective trials failed to demonstrate any significant benefits (either on blood pressure control or on renal function protection) of the revascularization over current antihypertensive therapy. Today many patients with RVH remain undetected for years because they are treated successfully and at low expense with these new blockers of RAAS. In addition to its well-known role in hemodynamics, angiotensin II promotes activations of profibrogenic and inflammatory factors and cells and stimulates reactive oxygen species generation. The "atherosclerotic milieu" itself plays a role in the loss of renal microvessels and defective angiogenesis. After an "adaptative" phase, ischemia eventually develops and induces hypoxia, the substratum of ischemic nephropathy. Because blood oxygen level-dependent MRI may provide an index of oxygen content in vivo, it may be useful to predict renal function outcome after percutaneous transluminal renal angioplasty. New PET tracers, dedicated to assess RAAS receptors, inflammatory cell infiltrates, angiogenesis, and apoptose, would be tested in this context of atherosclerotic renovascular disease.
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Affiliation(s)
- Alain Prigent
- Service de Biophysique et Médecine Nucléaire, AP-HP Hôpitaux Universitaires Paris-Sud Bicêtre, Paris, France.
| | - Philippe Chaumet-Riffaud
- Service de Biophysique et Médecine Nucléaire, AP-HP Hôpitaux Universitaires Paris-Sud Bicêtre, Paris, France; IR4M UMR8081 CNRS, Université Paris-Sud, Orsay, France
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38
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Alderson HV, Ritchie JP, Kalra PA. Revascularization as a treatment to improve renal function. Int J Nephrol Renovasc Dis 2014; 7:89-99. [PMID: 24600242 PMCID: PMC3933706 DOI: 10.2147/ijnrd.s35633] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
An aging atherosclerosis-prone population has led to an increase in the prevalence of atherosclerotic renovascular disease (ARVD). Medical management of this disease, as with other atherosclerotic conditions, has improved over the past decade. Despite the widespread availability of endovascular revascularization procedures, there is inconsistent evidence of benefit in ARVD and no clear consensus of opinion as to the best way to select suitable patients for revascularization. Several published randomized controlled trials have attempted to provide clearer evidence for best practice in ARVD, but they have done so with varying clarity and success. In this review, we provide an overview of ARVD and its effect on renal function. We present the currently available evidence for best practice in the management of patients with ARVD with a particular focus on revascularization as a treatment to improve renal function. We provide a brief overview of the evidence for revascularization in other causes of renal artery stenosis.
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Affiliation(s)
- Helen V Alderson
- The University of Manchester, Manchester Academic Health Sciences Centre, Vascular Research Group, Department of Renal Medicine, Salford Royal NHS Foundation Trust, Salford, UK
| | - James P Ritchie
- The University of Manchester, Manchester Academic Health Sciences Centre, Vascular Research Group, Department of Renal Medicine, Salford Royal NHS Foundation Trust, Salford, UK
| | - Philip A Kalra
- The University of Manchester, Manchester Academic Health Sciences Centre, Vascular Research Group, Department of Renal Medicine, Salford Royal NHS Foundation Trust, Salford, UK
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39
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Lal H, Helavar RV, Gamanagatti S, Jain S, Kumar R. Imaging in renal transplant: Review. INDIAN JOURNAL OF TRANSPLANTATION 2014. [DOI: 10.1016/j.ijt.2014.01.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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40
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Evans RG, Harrop GK, Ngo JP, Ow CPC, O'Connor PM. Basal renal O2 consumption and the efficiency of O2 utilization for Na+ reabsorption. Am J Physiol Renal Physiol 2014; 306:F551-60. [PMID: 24431201 DOI: 10.1152/ajprenal.00473.2013] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We examined how the presence of a fixed level of basal renal O2 consumption (Vo2(basal); O2 used for processes independent of Na(+) transport) confounds the utility of the ratio of Na(+) reabsorption (TNa(+)) to total renal Vo2 (Vo2(total)) as an index of the efficiency of O2 utilization for TNa(+). We performed a systematic review and additional experiments in anesthetized rabbits to obtain the best possible estimate of the fractional contribution of Vo2(basal) to Vo2(total) under physiological conditions (basal percent renal Vo2). Estimates of basal percent renal Vo2 from 24 studies varied from 0% to 81.5%. Basal percent renal Vo2 varied with the fractional excretion of Na(+) (FENa(+)) in the 14 studies in which FENa(+) was measured under control conditions. Linear regression analysis predicted a basal percent renal Vo2 of 12.7-16.5% when FENa(+) = 1% (r(2) = 0.48, P = 0.001). Experimentally induced changes in TNa(+) altered TNa(+)/Vo2(total) in a manner consistent with theoretical predictions. We conclude that, because Vo2(basal) represents a significant proportion of Vo2(total), TNa(+)/Vo2(total) can change markedly when TNa(+) itself changes. Therefore, caution should be taken when TNa(+)/Vo2(total) is interpreted as a measure of the efficiency of O2 utilization for TNa(+), particularly under experimental conditions where TNa(+) or Vo2(total) changes.
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Affiliation(s)
- Roger G Evans
- Dept. of Physiology, PO Box 13F, Monash Univ., Victoria 3800, Australia.
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41
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Ebrahimi B, Textor SC, Lerman LO. Renal relevant radiology: renal functional magnetic resonance imaging. Clin J Am Soc Nephrol 2013; 9:395-405. [PMID: 24370767 DOI: 10.2215/cjn.02900313] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Because of its noninvasive nature and provision of quantitative measures of a wide variety of physiologic parameters, functional magnetic resonance imaging (MRI) shows great potential for research and clinical applications. Over the past decade, application of functional MRI extended beyond detection of cerebral activity, and techniques for abdominal functional MRI evolved. Assessment of renal perfusion, glomerular filtration, interstitial diffusion, and parenchymal oxygenation turned this modality into an essential research and potentially diagnostic tool. Variations in many renal physiologic markers can be detected using functional MRI before morphologic changes become evident in anatomic magnetic resonance images. Moreover, the framework of functional MRI opened a window of opportunity to develop novel pathophysiologic markers. This article reviews applications of some well validated functional MRI techniques, including perfusion, diffusion-weighted imaging, and blood oxygen level-dependent MRI, as well as some emerging new techniques such as magnetic resonance elastography, which might evolve into clinically useful tools.
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Affiliation(s)
- Behzad Ebrahimi
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
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42
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Eirin A, Lerman LO. Darkness at the end of the tunnel: poststenotic kidney injury. Physiology (Bethesda) 2013; 28:245-53. [PMID: 23817799 DOI: 10.1152/physiol.00010.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal artery stenosis remains an important contributor to renal failure in the elderly population, but uncertainty continues to surround the mechanisms underlying progressive renal dysfunction. Here, we present the current understanding of the pathogenic mechanisms responsible for renal injury in these patients, with emphasis on those involved in disease progression.
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Affiliation(s)
- Alfonso Eirin
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
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43
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Charlton JR, Beeman SC, Bennett KM. MRI-detectable nanoparticles: the potential role in the diagnosis of and therapy for chronic kidney disease. Adv Chronic Kidney Dis 2013; 20:479-87. [PMID: 24206600 DOI: 10.1053/j.ackd.2013.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 05/23/2013] [Accepted: 06/03/2013] [Indexed: 12/30/2022]
Abstract
Chronic kidney disease (CKD) is a common, deadly, and expensive threat to public health. Patients susceptible to the development of CKD are difficult to identify because there are few noninvasive clinical techniques and markers to assess early kidney dysfunction. Noninvasive imaging techniques are being developed to quantitatively measure kidney morphology and function in preclinical research and in clinical trials. Magnetic resonance imaging (MRI) techniques in particular have the potential to provide structural and functional information in the kidney. Novel molecular imaging techniques, using targeted magnetic nanoparticles that exploit the characteristics of the endogenous protein, ferritin, have been developed in conjunction with MRI to count every perfused glomerulus in the kidney and measure their individual volumes. This technique could open the door to the possibility of prospectively assessing and eventually reducing a patient's risk for progression to CKD. This review highlights the potential clinical benefits of early detection in patients predisposed to CKD and discusses technologic and regulatory hurdles to the translation of these molecular MRI techniques to provide early diagnosis of CKD.
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44
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Ebrahimi B, Crane JA, Knudsen BE, Macura SI, Grande JP, Lerman LO. Evolution of cardiac and renal impairment detected by high-field cardiovascular magnetic resonance in mice with renal artery stenosis. J Cardiovasc Magn Reson 2013; 15:98. [PMID: 24160179 PMCID: PMC3874758 DOI: 10.1186/1532-429x-15-98] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 10/16/2013] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND Renal artery stenosis (RAS) promotes hypertension and cardiac dysfunction. The 2-kidney, 1-clip mouse model in many ways resembles RAS in humans and is amenable for genetic manipulation, but difficult to evaluate noninvasively. We hypothesized that cardiovascular magnetic resonance (CMR) is capable of detecting progressive cardiac and renal dysfunction in mice with RAS and monitoring the progression of the disease longitudinally. METHODS RAS was induced at baseline in eighteen mice by constricting the renal artery. Nine additional animals served as normal controls. CMR scans (16.4 T) were performed in all mice one week before and 2 and 4 weeks after baseline. Renal volumes and hemodynamics were assessed using 3D fast imaging with steady-state precession and arterial spin labelling, and cardiac function using CMR cine. Renal hypoxia was investigated using blood oxygen-level dependent (BOLD) MR. RESULTS Two weeks after surgery, mean arterial pressure was elevated in RAS mice. The stenotic kidney (STK) showed atrophy, while the contra-lateral kidney (CLK) showed hypertrophy. Renal blood flow (RBF) and cortical oxygenation level declined in the STK but remained unchanged in CLK. Moreover, cardiac end-diastolic and stroke volumes decreased and myocardial mass increased. At 4 weeks, STK RBF remained declined and the STK cortex and medulla showed development of hypoxia. Additionally, BOLD detected a mild hypoxia in CLK cortex. Cardiac end-diastolic and stroke volumes remained reduced and left ventricular hypertrophy worsened. Left ventricular filling velocities (E/A) indicated progression of cardiac dysfunction towards restrictive filling. CONCLUSIONS CMR detected longitudinal progression of cardiac and renal dysfunction in 2K, 1C mice. These observations support the use of high-field CMR to obtain useful information regarding chronic cardiac and renal dysfunction in small animals.
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MESH Headings
- Animals
- Arterial Pressure
- Atrophy
- Cardio-Renal Syndrome/diagnosis
- Cardio-Renal Syndrome/etiology
- Cardio-Renal Syndrome/physiopathology
- Disease Models, Animal
- Disease Progression
- Heart Rate
- Hypertension, Renovascular/diagnosis
- Hypertension, Renovascular/etiology
- Hypertension, Renovascular/physiopathology
- Hypertrophy
- Hypertrophy, Left Ventricular/diagnosis
- Hypertrophy, Left Ventricular/etiology
- Hypertrophy, Left Ventricular/physiopathology
- Kidney/blood supply
- Kidney/pathology
- Magnetic Resonance Imaging, Cine
- Male
- Mice
- Mice, 129 Strain
- Predictive Value of Tests
- Renal Artery Obstruction/complications
- Renal Artery Obstruction/diagnosis
- Renal Artery Obstruction/physiopathology
- Renal Circulation
- Time Factors
- Ventricular Dysfunction, Left/diagnosis
- Ventricular Dysfunction, Left/etiology
- Ventricular Dysfunction, Left/physiopathology
- Ventricular Function, Left
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Affiliation(s)
- Behzad Ebrahimi
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA
| | - John A Crane
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA
| | - Bruce E Knudsen
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
| | - Slobodan I Macura
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota, USA
| | - Joseph P Grande
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA
| | - Lilach O Lerman
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA
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Liss P, Cox EF, Eckerbom P, Francis ST. Imaging of intrarenal haemodynamics and oxygen metabolism. Clin Exp Pharmacol Physiol 2013; 40:158-67. [PMID: 23252679 DOI: 10.1111/1440-1681.12042] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 12/07/2012] [Accepted: 12/12/2012] [Indexed: 01/07/2023]
Abstract
The interruption of blood flow results in impaired oxygenation and metabolism. This can lead to electrophysiological changes, functional impairment and symptoms in quick succession. Quantitative measures of organ perfusion, perfusion reserve and tissue oxygenation are crucial to assess normal tissue metabolism and function. Magnetic resonance imaging (MRI) provides a number of quantitative methods to assess physiology in the kidney. Blood oxygenation level-dependent (BOLD) MRI provides a method for the assessment of oxygenation. Blood flow to the kidney can be assessed using phase contrast MRI. Dynamic contrast-enhanced MRI and arterial spin labelling (ASL) provide methods to assess tissue perfusion, ASL using the magnetization of endogenous water protons and thus providing a non-invasive method to assess perfusion. The application of diffusion-weighted MRI allows molecular motion in the kidney to be measured. Novel techniques can also be used to assess oxygenation in the renal arteries and veins and, combined with flow measures, provide an estimation of oxygen metabolism. Magnetic resonance imaging provides a synergy of non-invasive techniques to study renal function and the demand for these techniques is likely to be driven by the incentive to avoid the use of contrast media, to avoid radiation and to avoid complications with intervention procedures.
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Affiliation(s)
- Per Liss
- Department of Radiology, Center for Medical Imaging, Uppsala University Hospital, Uppsala University, Uppsala, Sweden
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46
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Sattur S, Prasad H, Bedi U, Kaluski E, Stapleton DD. Renal artery stenosis - an update. Postgrad Med 2013; 125:43-50. [PMID: 24113662 DOI: 10.3810/pgm.2013.09.2700] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Renal artery stenosis (RAS) is a common form of peripheral arterial disease. The most common cause of RAS is atherosclerosis. It is predominantly unilateral. The pathophysiologic mechanism stems from renal underperfusion resulting in the activation of the renin- angiotensin-aldosterone pathway. Even though the majority of patients with RAS are asymptomatic, it can clinically present with hypertension, nephropathy and congestive heart failure. This progressive disease can lead to resistant hypertension and end stage kidney failure. Screening patients for RAS with either Doppler ultrasonography, computed tomographic angiography, or magnetic resonance angiography is preferred. Adequate blood pressure control, goal-directed lipid-lowering therapy, smoking cessation, and other preventive measures form the foundation of management of patients with RAS. Catheter-based percutaneous revascularization with angioplasty and stenting showed modest clinical benefit for patients in small retrospective studies, but data from randomized clinical trials failed to confirm these beneficial results. The current ongoing Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial may provide more concrete data regarding the role of stenting in RAS. Surgical revascularization is considered only if catheter-based revascularization is unsuitable or unsuccessful. The American College of Cardiology/American Heart Association guidelines on evaluation and management of patients with RAS provide the framework for determining individualized assessment and treatment plans for patients with RAS.
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Hu L, Chen J, Yang X, Senpan A, Allen JS, Yanaba N, Caruthers SD, Lanza GM, Hammerman MR, Wickline SA. Assessing intrarenal nonperfusion and vascular leakage in acute kidney injury with multinuclear (1) H/(19) F MRI and perfluorocarbon nanoparticles. Magn Reson Med 2013; 71:2186-96. [PMID: 23929727 DOI: 10.1002/mrm.24851] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 05/20/2013] [Accepted: 06/02/2013] [Indexed: 01/19/2023]
Abstract
PURPOSE We sought to develop a unique sensor-reporter approach for functional kidney imaging that employs circulating perfluorocarbon nanoparticles and multinuclear (1) H/(19) F MRI. METHODS (19) F spin density weighted and T1 weighted images were used to generate quantitative functional mappings of both healthy and ischemia-reperfusion (acute kidney injury) injured mouse kidneys. (1) H blood-oxygenation-level-dependent (BOLD) MRI was also employed as a supplementary approach to facilitate the comprehensive analysis of renal circulation and its pathological changes in acute kidney injury. RESULTS Heterogeneous blood volume distributions and intrarenal oxygenation gradients were confirmed in healthy kidneys by (19) F MRI. In a mouse model of acute kidney injury, (19) F MRI, in conjunction with blood-oxygenation-level-dependent MRI, sensitively delineated renal vascular damage and recovery. In the cortico-medullary junction region, we observed 25% lower (19) F signal (P < 0.05) and 70% longer (1) H T2* (P < 0.01) in injured kidneys compared with contralateral kidneys at 24 h after initial ischemia-reperfusion injury. We also detected 71% higher (19) F signal (P < 0.01) and 40% lower (1) H T2* (P < 0.05) in the renal medulla region of injured kidneys compared with contralateral uninjured kidneys. CONCLUSION Integrated (1) H/(19) F MRI using perfluorocarbon nanoparticles provides a multiparametric readout of regional perfusion defects in acutely injured kidneys.
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Affiliation(s)
- Lingzhi Hu
- Department of Physics, Washington University in St. Louis, St. Louis, Missouri, USA
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48
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Blockade of the renin-angiotensin system in hypertensive patients with atherosclerotic renal artery stenosis. Curr Hypertens Rep 2013; 15:497-505. [PMID: 23897422 DOI: 10.1007/s11906-013-0376-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Renin angiotensin system (RAS) blockers are generally considered as contraindicated when an atheromatous renal artery stenosis (ARAS) is diagnosed. The main reason is the fear of inducing renal ischemia and, hence, accelerating renal fibrosis and the progression towards end stage renal disease, albeit RAS blocker have been shown to be highly effective in controlling blood pressure. Part of the solution came by the development of the revascularization. There is now growing evidence showing no superiority of angioplasty over medical treatment on cardiovascular events and mortality, renal function and blood pressure control. Hence, RAS blockers resurfaced based on their proven beneficial effects on blood pressure control and cardiovascular prevention in high risk atherosclerotic patients. Thus, RAS blockers belong today to the standard treatment of hypertensive patients with ARAS. However they were not systematically prescribed in trials focusing on ARAS. The ongoing CORAL trial will give us further information on the place of this class of antihypertensive drugs in patients with ARAS.
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49
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Okusa MD, Jaber BL, Doran P, Duranteau J, Yang L, Murray PT, Mehta RL, Ince C. Physiological biomarkers of acute kidney injury: a conceptual approach to improving outcomes. CONTRIBUTIONS TO NEPHROLOGY 2013; 182:65-81. [PMID: 23689656 DOI: 10.1159/000349967] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The past 5-10 years have brought significant advances in the identification and validation of novel biochemical biomarkers in the prevention and treatment of acute kidney injury (AKI). These biochemical biomarkers remain research tools but we anticipate that soon they will be employed in clinical practice. A Consensus Conference held by the Acute Dialysis Quality Initiative (ADQI) recently reviewed the evidence, and identified gaps and a research agenda. Furthermore, at this meeting was the birth of an initiative to comprehensively identify new opportunities to characterize the physiological changes during the course of AKI based upon a conceptual framework for the detection and monitoring of renal ischemia-reperfusion injury. This framework includes a transition from monitoring physiological biomarkers of adequate renal perfusion, to pathophysiologic biomarkers of renal hypoperfusion, and finally biomarkers of kidney cell structural injury/damage. Techniques to measure physiological changes in AKI include several physiological variables that might be used in an interactive way to supplement clinical information and biochemical damage biomarkers in the diagnosis and management of AKI. This review summarizes the spectrum of physiological parameters and potential new physiological methods that enable identification of high-risk patients for AKI, facilitate early diagnosis, and differential diagnosis to guide therapeutic management and prognostication. Finally, we propose a research agenda for the next 5 years to facilitate the development and validation of physiological biomarkers in AKI.
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Affiliation(s)
- Mark D Okusa
- Division of Nephrology and Center for Immunity, Inflammation and Regenerative Medicine, University of Virginia, Charlottesville, Va., USA.
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50
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Pohlmann A, Cantow K, Hentschel J, Arakelyan K, Ladwig M, Flemming B, Hoff U, Persson PB, Seeliger E, Niendorf T. Linking non-invasive parametric MRI with invasive physiological measurements (MR-PHYSIOL): towards a hybrid and integrated approach for investigation of acute kidney injury in rats. Acta Physiol (Oxf) 2013; 207:673-89. [PMID: 23336404 DOI: 10.1111/apha.12065] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 12/17/2012] [Accepted: 01/16/2013] [Indexed: 01/11/2023]
Abstract
Acute kidney injury of various origins shares a common link in the pathophysiological chain of events: imbalance between renal medullary oxygen delivery and oxygen demand. For in vivo assessment of kidney haemodynamics and oxygenation in animals, quantitative but invasive physiological methods are established. A very limited number of studies attempted to link these invasive methods with parametric Magnetic Resonance Imaging (MRI) of the kidney. Moreover, the validity of parametric MRI (pMRI) as a surrogate marker for renal tissue perfusion and renal oxygenation has not been systematically examined yet. For this reason, we set out to combine invasive techniques and non-invasive MRI in an integrated hybrid setup (MR-PHYSIOL) with the ultimate goal to calibrate, monitor and interpret parametric MR and physiological parameters by means of standardized interventions. Here we present a first report on the current status of this multi-modality approach. For this purpose, we first highlight key characteristics of renal perfusion and oxygenation. Second, concepts for in vivo characterization of renal perfusion and oxygenation are surveyed together with the capabilities of MRI for probing blood oxygenation-dependent tissue stages. Practical concerns evoked by the use of strong magnetic fields in MRI and interferences between MRI and invasive physiological probes are discussed. Technical solutions that balance the needs of in vivo physiological measurements together with the constraints dictated by small bore MR scanners are presented. An early implementation of the integrated MR-PHYSIOL approach is demonstrated including brief interventions of hypoxia and hyperoxia.
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Affiliation(s)
- A. Pohlmann
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin; Germany
| | - K. Cantow
- Institute of Physiology; Charité - Universitätsmedizin Berlin; Campus Mitte, and Center for Cardiovascular Research; Berlin; Germany
| | - J. Hentschel
- Berlin Ultrahigh Field Facility (B.U.F.F.); Max Delbrück Center for Molecular Medicine; Berlin; Germany
| | | | - M. Ladwig
- Institute of Physiology; Charité - Universitätsmedizin Berlin; Campus Mitte, and Center for Cardiovascular Research; Berlin; Germany
| | - B. Flemming
- Institute of Physiology; Charité - Universitätsmedizin Berlin; Campus Mitte, and Center for Cardiovascular Research; Berlin; Germany
| | - U. Hoff
- Nephrology and Intensive Care Medicine; Charité - Universitätsmedizin Berlin; Campus Virchow-Klinikum, and Center for Cardiovascular Research; Berlin; Germany
| | - P. B. Persson
- Institute of Physiology; Charité - Universitätsmedizin Berlin; Campus Mitte, and Center for Cardiovascular Research; Berlin; Germany
| | - E. Seeliger
- Institute of Physiology; Charité - Universitätsmedizin Berlin; Campus Mitte, and Center for Cardiovascular Research; Berlin; Germany
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