Increased Renal Arterial Resistance Predicts the Course of Renal Function in Type 2 Diabetes With Microalbuminuria

Diabetes and Renal Complications: An Overview on Pathophysiology, Biomarkers and Therapeutic Interventions

Diabetic kidney disease (DKD) is a major microvascular complication of both type 1 and type 2 diabetes. DKD is characterised by injury to both glomerular and tubular compartments, leading to kidney dysfunction over time. It is one of the most common causes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Persistent high blood glucose levels can damage the small blood vessels in the kidneys, impairing their ability to filter waste and fluids from the blood effectively. Other factors like high blood pressure (hypertension), genetics, and lifestyle habits can also contribute to the development and progression of DKD. The key features of renal complications of diabetes include morphological and functional alterations to renal glomeruli and tubules leading to mesangial expansion, glomerulosclerosis, homogenous thickening of the glomerular basement membrane (GBM), albuminuria, tubulointerstitial fibrosis and progressive decline in renal function. In advanced stages, DKD may require treatments such as dialysis or kidney transplant to sustain life. Therefore, early detection and proactive management of diabetes and its complications are crucial in preventing DKD and preserving kidney function.

Association of Preoperative Renal-Resistive Index With Long-term Renal and Cardiovascular Outcomes After Cardiac Surgery

OBJECTIVE

To investigate the association of elevated preoperative renal-resistive index (RRI) with persistent renal dysfunction, major adverse kidney events (MAKE), and major adverse cardiovascular events (MACE) after cardiac surgery.

DESIGN

Observational cohort study.

SETTING

University hospital.

PARTICIPANTS

Ninety-six adult patients undergoing cardiac surgery.

INTERVENTIONS

RRI measurement the day before surgery.

MEASUREMENTS AND MAIN RESULTS

Fifty-eight patients (60%) had elevated RRI ≥0.70. Five years after surgery, persistent renal dysfunction (sustained decline in estimated glomerular filtration rate ≥25%) had occurred in 25 patients (26%), MAKE (persistent renal dysfunction, renal replacement therapy, or death) in 34 (35%), and MACE (myocardial infarction, unstable angina, decompensated heart failure, stroke, or cardiovascular death) in 28 (29%). RRI was higher in patients who developed persistent renal dysfunction (median, 0.78 [IQR, 0.74-0.82] v 0.70 [0.66-0.77], p = 0.001), MAKE (0.77 [0.72-0.81] v 0.68 [0.65-0.76], p = 0.002), and MACE (0.77 [0.72-0.81] v 0.70 [0.66-0.77], p = 0.006). Patients with elevated RRI had a significantly higher cumulative incidence of all long-term outcomes. After adjustment for baseline renal function and heart failure, elevated RRI was associated with persistent renal dysfunction (hazard ratio [HR], 5.82 [95% CI, 1.71-19.9]), MAKE (HR, 4.21 [1.59-11.1]), and MACE (HR, 2.81 [1.03-7.65]).

CONCLUSIONS

Elevated preoperative RRI is associated with persistent renal dysfunction, MAKE, and MACE after cardiac surgery. Preoperative RRI may be used for long-term risk assessment in patients undergoing cardiac surgery.

Association of renal resistive indices with kidney disease progression and mortality

BACKGROUND

Renal resistive indices (RRI) have been shown to predict the progression of kidney disease. This study aims to evaluate the association of RRI with mortality and dialysis initiation after adjustment to therapeutic and life style interventions.

METHODS

This is a retrospective study that included all chronic kidney disease patients followed for at least two years in three nephrology clinics between 2006 and 2019 and who had a RRI level in their files. Kaplan Meier and log rank test compared the survival of patients with normal versus high RRI. Cox regression analysis evaluated the association between RRI and death or dialysis initiation after adjustment to treatments and life style modifications.

RESULTS

A total of 192 patients were analyzed: 68 had RRI < 0.7 and 124 had RRI ≥ 0.7. Their mean age was 66.5 ± 13.1 years at first visit, 78.1% were males. There was a negative correlation between baseline eGFR and RRI (p < 0.001; Spearman correlation coefficient = -0.521). The survival was significantly better in patients with RRI < 0.7 with a Log Rank test < 0.001. The univariate cox regression analysis showed a significant association between RRI and mortality (HR = 1.08; 95%CI: 1.04-1.11; p < 0.001) that remained significant after adjustment to cardiovascular risk factors and interventions such as salt reduction, blood pressure control, statins and RAAS inhibitors (HR = 1.04; 95%CI: 1.00-1.08; p = 0.036). Cox regression analysis showed a significant association between RRI and dialysis initiation (HR = 1.06; 95%CI 1.01-1.10; p = 0.011).

CONCLUSION

Our study revealed that patients with an elevated RRI ≥ 0.7 are at a higher risk of mortality after adjustment to medications and lifestyle modifications. RRI can, according to this study, be considered as an independent prognostic factor in CKD patients.

Research on the correlation between the renal resistive index, renal microvessel density, and fibrosis

BACKGROUND

This study was designed to investigate the relationship between the renal resistive index (RRI), renal microvessel density (RMD), and fibrosis in patients with chronic kidney disease (CKD).

METHODS

A total of 73 CKD patients were included in the study. Prior to kidney biopsy, we recorded the RRI of the interlobar artery and the estimated glomerular filtration rate (eGFR). Immunohistochemical analysis was performed to assess CD34 expression, and Masson staining was used to evaluate histopathological specimens for RMD and the degree of fibrosis. The percentage of the positive area (PPA) was recorded. Subsequently, we investigated the correlation between RRI, RMD, and kidney fibrosis.

RESULTS

RMD (CD34 PPA-total and CD34 PPA-peritubular capillary) showed a slight increase in early CKD stages (1-2) and gradually declined from CKD stages 2 to 5. No correlation was observed between the RRI and RMD or between the RRI and fibrosis across CKD stages 1 to 5. However, across CKD stages 2 to 5, RRI negatively correlated with CD34 PPA-glomerulus (r = -0.353, p = 0.022), but no correlation was found with CD34 PPA-total, CD34 PPA-peritubular capillary, or kidney fibrosis. eGFR showed a positive correlation with RMD (CD34 PPA-total, CD34 PPA-peritubular capillary, and CD34 PPA-glomerulus) across CKD stages 2 to 5, while no correlation was found from CKD stages 1 to 5.

CONCLUSION

There was no correlation between RRI and RMD or between RRI and fibrosis across CKD stages 1 to 5 (RRI ≤ 0.7).

Blood pressure and vascular determinants of glomerular filtration rate decline in diabetic kidney disease

Objective

In patients with type 2 diabetes and diabetic kidney disease (DKD), explore the relationship between estimated glomerular filtration rate decline (eGFR-d) and simultaneously assessed vascular risk markers including office, ambulatory or central blood pressure, pulse pressure, carotid-femoral pulse wave velocity (PWV), carotid intima-media thickness (IMT) and renal resistive indexes (RRI).

Research design and methods

At baseline, vascular risk markers were measured in addition to the routine clinical workup. The eGFR-d was based on 2000-2019 creatinine values. Parameters were compared by eGFR-d quartiles. Regression models of eGFR-d and vascular markers were assessed.

Results

In total, 135 patients were included. Mean age was 63.8 ± 10.8y, baseline eGFR 60.2 ± 26.4 ml/min/1.73 m2 and urine albumin-creatinine ratio (ACR) 49 ± 108 mg/mmol. Mean eGFR-d was based on 43 ± 39 creatinine values within a time span of 7.0 ± 1.9y. The average yearly eGFR decline was -1.8 ± 3.0 ml/min/1.73 m2 ranging from -5.8 ± 2.3 in the first quartile to +1.4 ± 1.7 in the fourth quartile. Mean 24 h systolic (SBP) and diastolic (DBP) blood pressure were 126 ± 17 and 74 ± 9 mmHg. Mean PWV was 11.8 ± 2.8 m/s, RRI 0.76 ± 0.07 and IMT 0.77 ± 0.21 mm. SBP and pulse pressure correlated with eGFR-d but not DBP. 24 h SBP stood out as a stronger predictor of eGFR-d than office or central SBP. PWV and RRI correlated with eGFR decline in univariate, but not multivariate regression models including 24 SBP and ACR.

Conclusions

In this study, eGFR decline was highly variable in patients with type 2 diabetes and DKD. Twenty-four hour SBP provided an added value to the routine measurement of ACR in predicting eGFR decline, whereas PWV and RRI did not.

Current Insights into the Significance of the Renal Resistive Index in Kidney and Cardiovascular Disease

Initially, the renal resistive index (RRI) was investigated with the aim of improving diagnosis in kidney diseases, but this goal was not met. Recently, many papers have highlighted the prognostic significance of the RRI in chronic kidney disease: specifically, in estimating the revascularization success of renal artery stenoses or the evolution of the graft and the recipients in renal transplantation. Moreover, the RRI has become significant in the prediction of acute kidney injury in critically ill patients. Studies in renal pathology have revealed correlations of this index with parameters of systemic circulation. The theoretical and experimental premises of this connection were then reconsidered, and studies analyzing the link between RRI and arterial stiffness, central and peripheral pressure, and left ventricular flow were conducted with this purpose. Many data currently indicate that RRI is influenced more by pulse pressure and vascular compliance than by renal vascular resistance-assuming that RRI reflects the complex interplay between systemic circulation and renal microcirculation and should be considered a marker of systemic cardiovascular risk beyond its prognostic relevance for kidney disease. In this review, we overview the clinical research that reveals the implications of RRI in renal and cardiovascular disease.

Discoveries from the study of longstanding type 1 diabetes

Award programmes that acknowledge the remarkable accomplishments of long-term survivors with type 1 diabetes have naturally evolved into research programmes to determine the factors associated with survivorship and resistance to chronic complications. In this review, we present an overview of the methodological sources of selection bias inherent in survivorship research (selection of those with early-onset diabetes, incidence-prevalence bias and bias from losses to follow-up in cohort studies) and the breadth and depth of literature focusing on this special study population. We focus on the learnings from the study of longstanding type 1 diabetes on discoveries about the natural history of insulin production loss and microvascular complications, and mechanisms associated with them that may in future offer therapeutic targets. We detail descriptive findings about the prevalence of preserved insulin production and resistance to complications, and the putative mechanisms associated with such resistance. To date, findings imply that the following mechanisms exist: strategies to maintain or recover beta cells and their function; activation of specific glycolytic enzymes such as pyruvate kinase M2; modification of AGE production and processing; novel mechanisms for modification of renin-angiotensin-aldosterone system activation, in particular those that may normalise afferent rather than efferent renal arteriolar resistance; and activation and modification of processes such as retinol binding and DNA damage checkpoint proteins. Among the many clinical and public health insights, research into this special study population has identified putative mechanisms that may in future serve as therapeutic targets, knowledge that likely could not have been gained without studying long-term survivors.

Associations of Renal Augmented Velocity Index with Arterial Stiffness, Carotid Intima-Media Thickness and Blood Pressure, in Comparison with Renal Resistive Index

The augmented velocity index (Avi) is a new Doppler index associated with arterial stiffness. We examined associations of renal Avi with blood pressure (BP), aortic stiffness and carotid intima-media thickness (IMT), and compared its performance with that of resistive index (RI). One hundred forty-seven volunteers were recruited. Renal Avi had significant positive correlations with systolic BP (r = 0.37, p < 0.001), diastolic BP (r = 0.2, p = 0.016), mean arterial pressure (r = 0.29, p < 0.001), pulse pressure (r = 0.31, p < 0.001), carotid-femoral pulse wave velocity (r = 0.49, p < 0.001) and carotid IMT (r = 0.23, p = 0.005). RI correlated positively with pulse pressure (r = 0.3, p < 0.001) only. After adjustments for co-variables, the associations remained similar. Patients with abnormal BP values (≥130/80 mm Hg), IMT and aortic stiffness (≥1 standard deviation of mean value) had higher Avi than those with normal values, but not RI. In conclusion, renal Avi had stronger associations with BP, arterial stiffness and carotid IMT than RI in apparently healthy volunteers, and was significantly increased in abnormal patients.

Investigation of the relationship between sensorineural hearing loss and associated comorbidities in patients with chronic kidney disease: A nationwide, population-based cohort study

Hearing impairment was observed in patients with chronic kidney disease (CKD). Our purpose was to investigate the relationship between sensorineural hearing loss (SNHL) and associated comorbidities in the CKD population. We conducted a retrospective, population-based study to examine the risk of developing SNHL in patients with CKD. Population-based data from 2000–2010 from the Longitudinal Health Insurance Database of the Taiwan National Health Insurance Research Database was used in this study. The population sample comprised 185,430 patients who were diagnosed with CKD, and 556,290 without CKD to determine SNHL risk factors. Cox proportional hazard regression analysis demonstrated the CKD group had a significantly increased risk of SNHL compared with the non-CKD group [adjusted hazard ratio (HR), 3.42; 95% confidence interval (CI), 3.01–3.90, p < 0.001]. In the CKD group, the risk of SNHL (adjusted HR, 5.92) was higher among patients undergoing hemodialysis than among those not undergoing hemodialysis (adjusted HR, 1.40). Furthermore, subgroup analysis revealed an increased risk of SNHL in patients with CKD and comorbidities, including heart failure (adjusted HR, 7.48), liver cirrhosis (adjusted HR, 4.12), type 2 diabetes mellitus (adjusted HR, 3.98), hypertension (adjusted HR, 3.67), and chronic obstructive pulmonary disease (adjusted HR, 3.45). CKD is an independent risk of developing SNHL. Additionally, hemodialysis for uremia can increase the risk of SNHL. Cardiovascular, lung, liver, and metabolic comorbidities in CKD patients may further aggravate the risk of SNHL by inter-organ crosstalk. We should pay attention to SNHL in this high-risk population.

Measuring the Interaction Between the Macro- and Micro-Vasculature

Structural and functional dysfunction in both the macro- and microvasculature are a feature of essential hypertension. In a healthy cardiovascular system, the elastic properties of the large arteries ensure that pulsations in pressure and flow generated by cyclic left ventricular contraction are dampened, so that less pulsatile pressure and flow are delivered at the microvascular level. However, in response to aging, hypertension, and other disease states, arterial stiffening limits the buffering capacity of the elastic arteries, thus exposing the microvasculature to increased pulsatile stress. This is thought to be particularly pertinent to high flow/low resistance organs such as the brain and kidney, which may be sensitive to excess pressure and flow pulsatility, damaging capillary networks, and resulting in target organ damage. In this review, we describe the clinical relevance of the pulsatile interaction between the macro- and microvasculature and summarize current methods for measuring the transmission of pulsatility between the two sites.

Renal intraparenchymal resistive index: the ultrasonographic answer to many clinical questions

The use of renal resistive indices (RRIs) for the study of renal microcirculation has in the past been proposed for the identification of renal organ damage or even to specifically identify injury to some areas of the renal parenchyma. Nevertheless, according to the most recent evidences from literature this organ-based conception of RRIs has been proven to be partial and unable to explain the RRIs variations in clinical settings of sepsis or combined organ failure of primitively extrarenal origin or, more generally, the deep connection between RRIs and hemodynamic factors such as compliance and pulsatility of the large vessels. The aim of this review is to explain the physiopathological basis of RRIs determination and the most common interpretative errors in their analysis. Moreover, through a comprehensive vision of these Doppler indices, the traditional and emerging clinical application fields for RRIs are discussed.

Evaluation of Split Renal Function for Children with Kidney Diseases by Renal and Vascular Color Ultrasonography

Renal dynamic imaging and radionuclide renography use radioactivity to evaluate split renal function. We aimed to investigate the use of renal vascular color Doppler ultrasonography for evaluation of split renal function in children. Thirty-five children with unilateral kidney diseases were enrolled. For patients with unilateral renal tumor, peak systolic velocity (V_max = 113.04 ± 13.59 cm/s) and resistance index (RI = 0.73 ± 0.02) were higher on abnormal compared with normal sides (V_max = 86.03 ± 6.49 cm/s, RI = 0.62 ± 0.01), and blood perfusion was good, indicating compensatory enhancement in split renal function. For unilateral renal cyst, V_max (58.20 ± 7.38 cm/s) was lower on the abnormal compared with the normal (87.71 ± 14.83 cm/s) size, and perfusion was poor. For unilateral hydronephrosis and renal atrophy, the parameters were similar to those of renal cyst, suggesting a weakening of renal function. For unilateral renal agenesis, V_max (106.07 ± 13.07 cm/s) and RI (0.71 ± 0.05) were higher, and perfusion was good. Renal vascular color Doppler ultrasonography was superior in the evaluation of split renal function in children, without being invasive or radioactive.

Renal resistive index in hypertensive patients

Spectral Doppler ultrasonography provides the evaluation of renal resistive index (RRI), a noninvasive and reproducible measure to investigate arterial compliance and/or resistance. RRI seems to possess an important role in the evaluation of diverse cases of secondary hypertension. In essential hypertension, RRI is associated with subclinical markers of target organ damage and reflects renal disease progression beyond albuminuria and creatinine clearance. Also, RRI can estimate cardiovascular and renal risk. The evaluation of RRI may also help the therapeutic decisions. Given its simple assessment, RRI emerges as a simple method and a "multifunctional" tool that could help on the cardiovascular risk evaluation of the hypertensive patient.

Should renal color Doppler ultrasonography be a routine test in newly diagnosed hypertensive patient?

: European Society of Hypertension/European Society of Cardiology guidelines recommend calculation of estimated glomerular filtration rate and evaluation of urinary albumin excretion rate as routine tests in the initial evaluation and during the follow-up of all hypertensive patients. However, from a clinical point of view, renal ultrasound - a noninvasive, readily available and cheap imaging modality - could contribute to the better evaluation of a hypertensive patient by identifying common causes of secondary hypertension (HTN) originating from the kidney and more recently by detecting renal injury in severe or long-standing essential HTN by measuring renal resistive indexes. The purpose of this review is to summarize the actual evidence which could support a larger use of renal ultrasound in the work-up of patients with newly diagnosed HTN.

Dapagliflozin acutely improves endothelial dysfunction, reduces aortic stiffness and renal resistive index in type 2 diabetic patients: a pilot study

Background

Sodium-glucose cotransporter-2 inhibitors reduce blood pressure (BP) and renal and cardiovascular events in patients with type 2 diabetes through not fully elucidated mechanisms. Aim of this study was to investigate whether dapagliflozin is able to acutely modify systemic and renal vascular function, as well as putative mechanisms.

Methods

Neuro-hormonal and vascular variables, together with 24 h diuresis, urinary sodium, glucose, isoprostanes and free-water clearance were assessed before and after a 2-day treatment with dapagliflozin 10 mg QD in sixteen type 2 diabetic patients; data were compared with those obtained in ten patients treated with hydrochlorothiazide 12.5 mg QD. Brachial artery endothelium-dependent and independent vasodilation (by flow-mediated dilation) and pulse wave velocity were assessed. Renal resistive index was obtained at rest and after glyceryl trinitrate administration. Differences were analysed by repeated measures ANOVA, considering treatment as between factor and time as within factor; Bonferroni post hoc comparison test was also used.

Results

Dapagliflozin decreased systolic BP and induced an increase in 24 h diuresis to a similar extent of hydrochlorothiazide; 24 h urinary glucose and serum magnesium were also increased. 24 h urinary sodium and fasting blood glucose were unchanged. Oxidative stress was reduced, as by a decline in urinary isoprostanes. Flow-mediated dilation was significantly increased (2.8 ± 2.2 to 4.0 ± 2.1%, p < 0.05), and pulse-wave-velocity was reduced (10.1 ± 1.6 to 8.9 ± 1.6 m/s, p < 0.05), even after correction for mean BP. Renal resistive index was reduced (0.62 ± 0.04 to 0.59 ± 0.05, p < 0.05). These vascular modifications were not observed in hydrochlorothiazide-treated individuals.

Conclusions

An acute treatment with dapagliflozin significantly improves systemic endothelial function, arterial stiffness and renal resistive index; this effect is independent of changes in BP and occurs in the presence of stable natriuresis, suggesting a fast, direct beneficial effect on the vasculature, possibly mediated by oxidative stress reduction.

Increased renal resistive index in type 2 diabetes: Clinical relevance, mechanisms and future directions

Type 2 diabetes is a global health challenge. In type 2 diabetes both microvascular (nephropathy, retinopathy, neuropathy) and macrovascular complications arise. In kidney, renal pathological changes leading to diabetic nephropathy are mainly secondary to atherosclerosis of the intra and extra renal arteries together with microangiopathy of the glomerular capillaries, afferent arterioles and efferent arterioles. Renal resistive index (RRI) is defined as a ratio of the difference between maximum and minimum (end-diastolic) flow velocity to maximum flow velocity derived from the Doppler measurements of main renal and intrarenal (segmental/interlobar) arteries. Renal resistive index is tightly related to renal arteriolosclerosis, and represents an integrated index of arterial compliance, pulsatility and downstream microvascular impedance. In meantime, growing suggest that RRI has also been closely related with atherosclerosis. Most studies performed in type 2 diabetes showed RRI is increased in type 2 diabetes. In this review, we summarize the data regarding RRI with regard to performed studies, pathogenesis and prognosis, especially focusing on type 2 diabetes (T2D). We also review the data regarding the development of metabolic syndrome (MetS) and RRI.

Hemodynamics as Measured With Color Doppler Sonography in Early-Stage Obesity-Related Nephropathy in Children

OBJECTIVES

We retrospectively studied hemodynamic changes in the interlobar artery to assess the clinical value of color Doppler sonography for detecting preclinical obesity-related nephropathy.

METHODS

Color Doppler renal sonography was performed in 52 children with obesity-related nephropathy and 51 control children with simple obesity. The interlobar artery resistive index (RI) was measured and compared with clinical data and laboratory indicators.

RESULTS

The left RI (mean ± SD, 0.65 ± 0.05 versus 0.60 ± 0.08; t = 3.85), right RI (0.64 ± 0.03 versus 0.59 ± 0.02; t = 10.00), and mean RI (0.64 ± 0.05 versus 0.59 ± 0.06; t = 5.00) revealed large statistically significant increases in the obesity-related nephropathy group (all P < .01). In the obesity-related nephropathy group, a positive correlation was found between the mean RI and 24-hour urine trace albumin (r = 0.47; P < .01), triglycerides (r = 0.98; P < .01), and body mass index (r = 0.28; P < .05). The 24-hour urine trace albumin and triglycerides were higher in the obesity-related nephropathy group than the control group (P < .05). In the control group, a mild positive correlation was also found between the mean RI and body mass index (r = 0.24; P < .05).

CONCLUSIONS

Color Doppler sonography successfully indicated renal hemodynamic changes and has diagnostic value for early-stage obesity-related nephropathy.

Comparison between the effects of hydrochlorothiazide and indapamide on the kidney in hypertensive patients inadequately controlled with losartan

The aim of the study is to compare the effects of hydrochlorothiazide and indapamide on the kidney in patients with hypertension inadequately controlled with losartan. A total of 140 patients who met the criteria and inadequately controlled with losartan 50 mg per day for 2 weeks were randomized in two groups and administered either hydrochlorothiazide 12.5 mg per day (n=70) or indapamide (sustained release) 1.5 mg per day (n=70) in combination with losartan 50 mg per day. Office blood pressure (BP) were collected at baseline and upon each follow-up visit. Creatinine, urine albumin-creatinine ratio (ACR), urine neutrophil gelatinase-associated lipocalin (NGAL) and renal resistive index (RRI) were also collected at baseline and at the 24-week follow-up. None of the baseline characteristics was statistically significantly different between the two groups. After excluding those patients with office BP uncontrolled, 46 patients in the hydrochlorothiazide group (45.7% males, 58.8±10.8 years) and 44 patients in the indapamide group (38.4% males, 61.5±10.9 years) were analysed. There were insignificant changes in creatinine and significant decreases in ACR, NGAL and RRI compared to baseline levels in the two groups. The decrease in ACR (3.8 (0, 28.7) vs 4.2 (0.4, 64.8) mg g^-1, P=0.485) was not significantly different between the two groups, while the decrease in NGAL (16.07±7.07 vs 28.77±7.64 ng ml^-1, P<0.001) and RRI (0.04±0.02 vs 0.07±0.04, P<0.001) was more significant in the indapamide group than in the hydrochlorothiazide group. In conclusion, indapamide is superior to hydrochlorothiazide to improve renal tubular injury and renal haemodynamics in combination with losartan in hypertensive patients with controlled BP.

Phosphodiesterase-5 inhibition preserves renal hemodynamics and function in mice with diabetic kidney disease by modulating miR-22 and BMP7

Diabetic Nephropathy (DN) is the leading cause of end-stage renal disease. Preclinical and experimental studies show that PDE5 inhibitors (PDE5is) exert protective effects in DN improving perivascular inflammation. Using a mouse model of diabetic kidney injury we investigated the protective proprieties of PDE5is on renal hemodynamics and the molecular mechanisms involved. PDE5i treatment prevented the development of DN-related hypertension (P < 0.001), the increase of urine albumin creatinine ratio (P < 0.01), the fall in glomerular filtration rate (P < 0.001), and improved renal resistive index (P < 0.001) and kidney microcirculation. Moreover PDE5i attenuated the rise of nephropathy biomarkers, soluble urokinase-type plasminogen activator receptor, suPAR and neutrophil gelatinase-associated lipocalin, NGAL. In treated animals, blood vessel perfusion was improved and vascular leakage reduced, suggesting preserved renal endothelium integrity, as confirmed by higher capillary density, number of CD31⁺ cells and pericyte coverage. Analysis of the mechanisms involved revealed the induction of bone morphogenetic protein-7 (BMP7) expression, a critical regulator of angiogenesis and kidney homeostasis, through a PDE5i-dependent downregulation of miR-22. In conclusion PDE5i slows the progression of DN in mice, improving hemodynamic parameters and vessel integrity. Regulation of miR-22/BMP7, an unknown mechanism of PDE5is in nephrovascular protection, might represent a novel therapeutic option for treatment of diabetic complications.

Advances in the non-invasive assessment of vascular dysfunction in metabolic syndrome and diabetes: Focus on endothelium, carotid mechanics and renal vessels

AIM

The present paper is a selective review on the methodology and clinical significance of techniques to assess specifically endothelial function, carotid mechanics and renal vascular function, particularly in the light of vascular dysfunction in metabolic syndrome and type 2 diabetes.

DATA SYNTHESIS

Endothelial dysfunction appears to be earlier detectable in the microcirculation of patients with altered glucose metabolism, while it attains significance in the macrocirculation at more advanced disease stages. Smooth muscle cell dysfunction is now increasingly recognized to play a role both in the development of endothelial dysfunction and abnormal arterial distensibility. Furthermore, impaired glucose metabolism affects carotid mechanics through medial calcification, structural changes in extracellular matrix due to advanced glycation and modification of the collagen/elastin material stiffness. The assessment of renal vascular function by dynamic ultrasound or magnetic resonance imaging has recently emerged as an appealing target for identifying subtle vascular alterations responsible for the development of diabetic nephropathy.

CONCLUSIONS

Vascular dysfunction represents a major mechanism for the development of cardiovascular disease in patients with abnormal glucose metabolism. Hence, the currently available non-invasive techniques to assess early structural and vascular abnormalities merit recommendation in this population, although their predictive value and sensitivity to monitor treatment-induced changes have not yet been established and are still under investigation.

Assessment of renal perfusion with contrast-enhanced ultrasound: Preliminary results in early diabetic nephropathies

OBJECTIVE

We performed a prospective study to evaluate the value of contrast-enhanced ultrasound (CEUS) in quantitative evaluation of renal cortex perfusion in patients suspected of early diabetic nephropathies (DN), with the estimated GFR (MDRD equation) as the gold standard.

METHODS

The study protocol was approved by the hospital review board; each patient gave written informed consent. Our study included 46 cases (21 males and 25 females, mean age 55.6 ± 4.14 years) of clinical confirmed early DN patients. After intravenous bolus injection of 1 ml sulfur hexafluoride microbubbles of ultrasound contrast agent, real time CEUS of renal cortex was performed successively using a 2-5 MHz convex probe. Time-intensity curves (TICs) and quantitative indexes were created with Qlab software. Receiver operating characteristic (ROC) curves were used to predict the diagnostic criteria of CEUS quantitative indexes, and their diagnostic efficiencies were compared with resistance index (RI) and peak systolic velocity (PSV) of renal segmental arteries by chi square test. Our control group included forty-five healthy volunteers. Difference was considered statistically significant with P <  0.05.

RESULTS

Changes of area under curve (AUC), derived peak intensity (DPI) were statistically significant (P <  0.05). DPI less than 12 and AUC greater than 1400 had high utility in DN, with 71.7% and 67.3% sensitivity, 77.8% and 80.0% specificity. These results were significantly better than those obtained with RI and PSV which had no significant difference in early stage of DN (P > 0.05).

CONCLUSIONS

CEUS might be helpful to improve early diagnosis of DN by quantitative analyses. AUC and DPI might be valuable quantitative indexes.

A pilot trial to examine the association between circulating endothelial cell levels and vascular injury in patients with diabetes and chronic kidney disease

Objective

While albuminuria is a marker for progressive chronic kidney disease (CKD) in patients with type 2 diabetes (T2DM), both albuminuric and normoalbuminuric patients appear prone to vascular injury. This pilot study examines the association between circulating endothelial cell (CEC) levels and vascular injury in patients with T2DM and CKD.

Methods

In this cross-sectional study, eligible adult patients had T2DM, and stage 3 CKD (estimated glomerular filtration rate between 30 and 60 mL/min/1.73m ²). CEC levels were tested by Janssen Diagnostics, LLC using an immuno-magnetic bead-based assay. CEC levels were compared to levels in a previously tested normal population. Correlations between CEC levels and other vascular injury markers (urine albumin, von-Willebrand factor antigen, hs-CRP, uric acid) were performed.

Results

Patients included 40 adults of which nineteen were normoalbuminuric.  Mean CEC levels (38.7, SD 38.1 cells) were significantly higher than the normal population (M = 21±18 cells, p<0.001; N = 249), including in the normoalbuminuric subgroup (M = 42.9±42.5 cells, p<0.001). CEC levels were significantly correlated with uric acid levels (r=0.33, p=0.039).

Conclusions

CEC levels in patients with T2DM and CKD, both albuminuric and normoalbuminuric, are significantly higher than a normal population, suggesting the presence of vascular injury in both groups. Future studies are needed to evaluate the role of CECs as a biomarker to predict outcomes in normoalbuminuric patients with CKD.

External Validation of the Kidney Failure Risk Equation and Re-Calibration with Addition of Ultrasound Parameters

BACKGROUND AND OBJECTIVES

Progression of CKD toward ESRD is heterogeneous. The Kidney Failure Risk Equation (KFRE) was developed to identify CKD patients at high risk of ESRD. We aimed to externally validate KFRE and to test whether the addition of predefined Duplex ultrasound markers - renal resistive index (RRI) or difference of resistive indices in spleen and kidney (DI-RISK) - improved ESRD prediction.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The prospective Cardiovascular and Renal Outcome in CKD 2-4 Patients-The Fourth Homburg evaluation (CARE FOR HOMe) study recruits CKD stage G2-G4 patients referred to a tertiary referral center for nephrologic care. Four hundred three CARE FOR HOMe participants enrolled between 2008 and 2012 had available RRI measurements at study inclusion; they were subsequently followed for a mean of 4.4±1.6 years. This subcohort was used to validate KFRE and to assess the added value of the ultrasound markers (new models KFRE+RRI and KFRE+DI-RISK). Model performance was assessed by log-likelihood ratio test, c-statistic, integrated discrimination improvement metrics (for study participants without subsequent ESRD [IDI No ESRD] and for patients with ESRD [IDI ESRD]), and calibration plots. If either new model improved on KFRE, we determined to validate it in an independent cohort of 162 CKD patients.

RESULTS

KFRE predicted ESRD in CARE FOR HOMe participants with a c-statistic of 0.91 (95% confidence interval, 0.83 to 0.99). Adding RRI improved the KFRE model (P<0.001), and the KFRE+RRI model was well calibrated; however, the c-statistic (0.91 [0.83-1.00]) was similar, and overall sensitivity (IDI No ESRD=0.05 [0.00-0.10]) or overall specificity (IDI ESRD=0.00 [0.00-0.01]) did not improve. Adding DI-RISK did not improve the KRFE model. In the external validation cohort, we confirmed that the KFRE+RRI model did not outperform KFRE.

CONCLUSIONS

Routine Duplex examinations among CKD patients did not improve risk prediction for progression to ESRD beyond a validated equation.

Renal Ultrasound (and Doppler Sonography) in Hypertension: An Update

Ultrasound (US) allows the non-invasive evaluation of morphological changes of kidney structure (by means of B-Mode) and patterns of renal and extrarenal vascularization (by means of color-Doppler and contrast-enhanced US). In hypertensive subjects it offers a relevant contribution to the diagnosis of early renal damage, acute or chronic nephropathies and nephrovascular disease. However, morphological changes are often detected late and non-specific and in recent years evidence has increased regarding the clinical relevance of renal resistive index (RRI) for the study of vascular and renal parenchymal renal abnormalities. RRI is measured by Doppler sonography in an intrarenal artery, as the difference between the peak systolic and end-diastolic blood velocities divided by the peak systolic velocity. At first RRI was proved to be a marker of renal disease onset and progression; later the influence of systemic vascular properties on RRI was shown and authors claimed its use as an independent predictor of cardiovascular risk rather than of renal damage. Indeed, renal vascular resistance is only one of several renal (vascular compliance, interstitial and venous pressure), and extrarenal (heart rate, pulse pressure) determinants that concur to determine RRI individual values but not the most important one. The clinical relevance of RRI measurement as a surrogate endpoint of specific renal damage or/and as surrogate endpoint of atherosclerotic diffuse vascular damage is still debated.To summarize, from the literature: (a) In hypertensives with normal renal function and no albuminuria, especially in younger people, RRI is an early marker of renal damage that is especially useful when hypertension and diabetes concur in the same subjects. In these subjects RRI could improve current clinical scores used to stratify early renal damage. In older subjects RRI increases in accordance with the increase in systemic vascular stiffness and, because of this close relationship, RRI is also a marker of systemic atherosclerotic burden and the role of renal determinants can weaken. The clinical relevance was not specifically investigated. (b) In transplant kidney and in chronic renal disease high (>0.80) RRI values can independently predict renal failure. The recent claim that systemic (pulse pressure) rather than renal hemodynamic determinants sustain this predictive role of RRI, does not significantly reduce this predictive role of RRI. (c) Doppler ultrasound allows diagnosis and grading of renal stenosis in both fibromuscolar dysplastic and atherosclerotic diseases. Moreover, by RRI assay Doppler ultrasound can indirectly measure the hemodynamic impact of renal artery stenosis on the homolateral kidney, by virtue of the stenosis-related decrease in pulse pressure. However, in elderly subjects with atherosclerotic renal artery stenosis coexisting renal diseases can independently increase RRI by the augmentation in renal vascular stiffness and tubulo-interstitial pressure and hidden changes due to renal artery stenosis.

The internist and the renal resistive index: truths and doubts

The renal resistive index (RRI) is measured by Doppler sonography in an intrarenal artery, and is the difference between the peak systolic and end-diastolic blood velocities divided by the peak systolic velocity. The RRI is used for the study of vascular and renal parenchymal renal abnormalities, but growing evidence indicates that it is also a dynamic marker of systemic vascular properties. Renal vascular resistance is only one of several renal (vascular compliance, interstitial and venous pressure), and extrarenal (heart rate, aortic stiffness, pulse pressure) determinants that combine to determine the RRI values, and not the most important one. RRI cannot always be considered a specific marker of renal disease. To summarize from the literature: (1) hydronephrosis, abdominal hypertension, renal vein thrombosis and acute kidney injury are all associated with an acute increase in interstitial and venous pressure that determine RRI values. In all these conditions, RRI is a reliable marker of the severity of renal damage. (2) The hemodynamic impact of renal artery stenosis can be assayed by the RRI decrease in the homolateral kidney by virtue of decreasing pulse pressure. However, renal diseases that often coexist, increase renal vascular stiffness and hide the hemodynamic effect of renal stenosis. (3) In transplant kidney and in chronic renal disease, high RRI values (>0.80) can independently predict renal and clinical outcomes, but systemic (pulse pressure) rather than renal hemodynamic determinants sustain the predictive role of RRI. (4) Higher RRI detects target renal organ damage in hypertension and diabetes when renal function is still preserved, as a marker of systemic atherosclerotic burden. Is this the fact? We attempt to answer.

Diabetes increases renovascular impedance in patients with liver cirrhosis

Renal failure is a common complication of cirrhosis and is associated with poor prognosis. Several reports have demonstrated the clinical utility of renal resistive indices in the assessment of renal function in cirrhosis patients. It is unknown whether the occurrence of diabetes affects renal haemodynamic indices in patients with cirrhosis. Therefore, the aim of our study was to compare renal Doppler indices in cirrhotic patients with and without type 2 diabetes mellitus (T2DM) and in diabetics without cirrhosis, and to relate the Doppler parameters to albuminuria. We evaluated 89 consecutive patients with normal renal functioning, including 37 with cirrhosis and T2DM (CD-Group), 41 with cirrhosis without diabetes (C-Group) and 11 with diabetes without cirrhosis (D-Group). The kidney pulsatility index (PI) and resistance index (RI) were measured by Doppler ultrasound. Renal function was expressed as the estimated glomerular filtration rate (eGFR) using the modification of diet in renal disease (MDRD) formula. Microalbuminuria (µAlb) was also evaluated. No significant differences were observed with respect to age, the Child-Pugh class or the serum creatinine level. The eGFR was mildly reduced in the CD-Group compared with the C-Group and D-Group, and µAlb was present in 24.4 % of the patients in the CD-Group and in 9 % of those in the D-Group. The PI and RI were significantly increased in the CD-Group and D-Group compared with the C-Group. Both the PI and RI were significantly associated with µAlb independent of age and Child-Pugh class. The novel finding of this study was that T2DM potentially impairs renal haemodynamics in patients with cirrhosis.

Renoprotective effects of berberine as adjuvant therapy for hypertensive patients with type 2 diabetes mellitus: Evaluation via biochemical markers and color Doppler ultrasonography

Diabetes and hypertension are complex and serious diseases that may ultimately lead to renal complications. Adequate control of blood glucose and blood pressure contributes to decreased renal risks, but may not be sufficient for certain patients. The current study was undertaken to investigate the renoprotective effects of berberine as an adjuvant therapy to standard hypotensive and hypoglycemic treatment in hypertensive patients with type 2 diabetes mellitus (T2DM). In this 2-year clinical study, 69 hypertensive patients with T2DM, whose blood pressure and fasting plasma glucose (FPG) were adequately controlled by hypotensive and oral hypoglycemic agents prior to the study, were enrolled and randomly assigned into control (33 cases) and add-on (36 cases) groups. Berberine was orally administrated to the patients in the add-on group concomitantly with standard hypotensive and hypoglycemic treatment. Baseline characteristics, including the levels of FPG, glycated hemoglobin, systolic blood pressure, diastolic blood pressure, serum creatinine, urinary albumin-to-creatine ratio (UACR), urinary osteopontin and kidney injury molecule-1 (KIM-1) were determined. Furthermore, the oxidative stress markers malondialdehyde, urinary 8-hydroxy-2'-deoxyguanosine, superoxide dismutase, glutathione peroxidase and total-antioxidant capacity, and the inflammatory parameters vascular adhesion molecule-1, C-reactive protein and high molecular weight-adiponectin were evaluated. In addition, ultrasonographic parameters, including peak systolic velocity, end diastolic velocity and renal arterial resistance index were determined. After treatment, it was observed that the control and add-on treatments were able to adequately control blood pressure and blood glucose. Patients in the add-on group exhibited significant reductions in renal damage biochemical markers (UACR, urinary osteopontin and KIM-1) and improved renal hemodynamics, in addition to reduced inflammation and oxidative stress. The present results suggest that berberine is beneficial for hypertensive patients with T2DM as add-on therapy to standard hypotensive and hypoglycemic agents.

Renal resistive index and mortality in chronic kidney disease

Renal resistive index (RRI) measured by Doppler ultrasonography is associated with cardiovascular events and mortality in hypertensive, diabetic, and elderly patients. We studied the factors associated with high RRI (≥0.70) and its associations with mortality in chronic kidney disease patients without renal artery stenosis. We included 1962 patients with an estimated glomerular filtration rate of 15 to 59 mL/min per 1.73 m(2) who also had RRI measured (January 1, 2005, to October 2011) from an existing chronic kidney disease registry. Participants with renal artery stenosis (60%-99% or renal artery occlusion) were excluded. Multivariable logistic regression model was used to study factors associated with high RRI (≥0.70), and its association with mortality was studied using Kaplan-Meier plots and Cox proportional hazards model. Hypertension was prevalent in >90% of the patients. In the multivariable logistic regression, older age, female sex, diabetes mellitus, coronary artery disease, peripheral vascular disease, higher systolic blood pressure, and the use of β blockers were associated with higher odds of having RRI≥0.70. During a median follow-up of 2.2 years, 428 patients died. After adjusting for covariates, RRI≥0.70 was associated with increased mortality (adjusted hazard ratio, 1.29; 95% confidence interval, 1.02-1.65; P<0.05). This association was more pronounced among younger patients and those with stage 3 chronic kidney disease. Noncardiovascular/non-malignancy-related deaths were higher in those with RRI≥0.70. RRI≥0.70 is associated with higher mortality in hypertensive chronic kidney disease patients without clinically significant renal artery stenosis after accounting for other significant risk factors. Its evaluation may allow early identification of those who are at risk thereby potentially preventing or delaying adverse outcomes.

Predictive value of dynamic renal resistive index (DRIN) for renal outcome in type 2 diabetes and essential hypertension: a prospective study

BACKGROUND

Hypertension (EH) and type 2 diabetes (T2DM) are major causes of chronic kidney disease (CKD) and identification of predictors of CKD onset is advisable. We aimed to assess whether dynamic renal resistive index (DRIN), as well as other markers of systemic vascular damage, are able to predict albuminuria onset and estimated glomerular filtration rate (eGFR) decline in patients with T2DM or EH.

METHODS

In this prospective observational cohort study, 27 T2DM and 43 EH patients, free of CKD at baseline, were followed-up for 4.1 ± 0.6 years. Resistive Index (RI), endothelium-dependent (FMD) and independent vasodilation in the brachial artery (after glyceryl trinitrate - GTN - 25 μg s.l.), carotid-femoral Pulse Wave Velocity (PWV), Augmentation Index (AIx), DRIN (%RI change after GTN 25 μg s.l.) were evaluated.

RESULTS

Patients developing microalbuminuria were older, more frequently T2DM, with higher UACR at baseline, and showed higher DRIN (-2.8 ± 6.7 vs -10.6 ± 6.4 %, p = 0.01) and PWV (9.9 ± 1.3 vs 7.9 ± 1.5 m/s, p = 0.004) at baseline. The best predictors of microalbuminuria onset were DRIN > -5.16 % in T2DM (sensitivity 0.83, specificity 0.80) and PWV > 8.6 m/s in EH (sensitivity 0.96, specificity 1.00). Individuals whose eGFR declined (n = 27) had higher eGFR at baseline, but similar vascular characteristics; however in EH showing eGFR decline, baseline DRIN and PWV were higher. PWV showed a steeper progression during follow-up in patients developing albuminuria (Visit-outcome interaction: p = 0.01), while DRIN was early compromised but no further impaired (Visit-outcome interaction: p = 0.04).

CONCLUSIONS

PWV and DRIN are able to predict microalbuminuria onset in newly diagnosed EH and T2DM. DRIN is early compromised in T2DM patients developing microalbuminuria.

Ultrasound Doppler renal resistive index: a useful tool for the management of the hypertensive patient

The Doppler-derived renal resistive index has been used for years in a variety of clinical settings such as the assessment of chronic renal allograft rejection, detection and management of renal artery stenosis, evaluation of progression risk in chronic kidney disease, differential diagnosis in acute and chronic obstructive renal disease, and more recently as a predictor of renal and global outcome in the critically ill patient. More recently, evidence has been accumulating showing that an increased renal resistive index not only reflects changes in intrarenal perfusion but is also related to systemic hemodynamics and the presence of subclinical atherosclerosis, and may thus provide useful prognostic information in patients with primary hypertension. On the basis of these results, the evaluation of renal resistive index has been proposed in the assessment and management of patients with primary hypertension to complement other signs of renal abnormalities.

Markers of and risk factors for the development and progression of diabetic kidney disease

Diabetic kidney disease (DKD) occurs in 25%-40% of patients with diabetes. Given the dual problems of a significant risk of progression from DKD to end-stage renal disease (ESRD) and increased cardiovascular morbidity and mortality, it is important to identify patients at risk of DKD and ESRD and initiate protective renal and cardiovascular therapies. The importance of preventive therapy is emphasized further by worldwide increases in the incidence of diabetes. This review summarizes the evidence regarding the prognostic value and benefits of targeting established and novel risk markers for DKD development and progression. Family history of DKD, smoking history, and glycemic, blood pressure, and plasma lipid level control are established factors for identifying people at greatest risk of DKD development and progression. Absolute albumin excretion rate (AER) and glomerular filtration rate (GFR) measurements also are important, although AER categorization generally lacks the necessary specificity and sensitivity, and estimates of declining GFR are compromised by methodological limitations for GFRs in the normal-to-high range. Emerging risk markers for progressive loss of kidney function include markers of oxidation and inflammation, profibrotic cytokines, uric acid, advanced glycation end products, functional and structural markers of vascular dysfunction, kidney structural changes, and tubular biomarkers. Among these, the most promising are serum uric acid and soluble tumor necrosis factor receptor (type 1 and type 2) levels, especially in relation to GFR changes. At present, these can only be considered as risk markers because they only identify an individual at increased risk of progressive DKD and not necessarily related to the causal pathway promoting kidney damage. Further work is needed to establish whether modulating these factors improves the prognosis in DKD. Although change in urinary peptidome levels also is a promising marker, there currently is neither a clinical assay nor adequate studies defining its prognostic value. Until these or other novel markers become available for clinical use, predictive accuracy often may be increased with greater attention to established markers.

Reference Values and Factors Associated With Renal Resistive Index in a Family-Based Population Study

Increased renal resistive index (RRI) has been recently associated with target organ damage and cardiovascular or renal outcomes in patients with hypertension and diabetes mellitus. However, reference values in the general population and information on familial aggregation are largely lacking. We determined the distribution of RRI, associated factors, and heritability in a population-based study. Families of European ancestry were randomly selected in 3 Swiss cities. Anthropometric parameters and cardiovascular risk factors were assessed. A renal Doppler ultrasound was performed, and RRI was measured in 3 segmental arteries of both kidneys. We used multilevel linear regression analysis to explore the factors associated with RRI, adjusting for center and family relationships. Sex-specific reference values for RRI were generated according to age. Heritability was estimated by variance components using the ASSOC program (SAGE software). Four hundred women (mean age±SD, 44.9±16.7 years) and 326 men (42.1±16.8 years) with normal renal ultrasound had mean RRI of 0.64±0.05 and 0.62±0.05, respectively ( P <0.001). In multivariable analyses, RRI was positively associated with female sex, age, systolic blood pressure, and body mass index. We observed an inverse correlation with diastolic blood pressure and heart rate. Age had a nonlinear association with RRI. We found no independent association of RRI with diabetes mellitus, hypertension treatment, smoking, cholesterol levels, or estimated glomerular filtration rate. The adjusted heritability estimate was 42±8% ( P <0.001). In a population-based sample with normal renal ultrasound, RRI normal values depend on sex, age, blood pressure, heart rate, and body mass index. The significant heritability of RRI suggests that genes influence this phenotype.

Intrarenal resistive index after renal transplantation

BACKGROUND

The intrarenal resistive index is routinely measured in many renal-transplantation centers for assessment of renal-allograft status, although the value of the resistive index remains unclear.

METHODS

In a single-center, prospective study involving 321 renal-allograft recipients, we measured the resistive index at baseline, at the time of protocol-specified renal-allograft biopsies (3, 12, and 24 months after transplantation), and at the time of biopsies performed because of graft dysfunction. A total of 1124 renal-allograft resistive-index measurements were included in the analysis. All patients were followed for at least 4.5 years after transplantation.

RESULTS

Allograft recipients with a resistive index of at least 0.80 had higher mortality than those with a resistive index of less than 0.80 at 3, 12, and 24 months after transplantation (hazard ratio, 5.20 [95% confidence interval {CI}, 2.14 to 12.64; P<0.001]; 3.46 [95% CI, 1.39 to 8.56; P=0.007]; and 4.12 [95% CI, 1.26 to 13.45; P=0.02], respectively). The need for dialysis did not differ significantly between patients with a resistive index of at least 0.80 and those with a resistive index of less than 0.80 at 3, 12, and 24 months after transplantation (hazard ratio, 1.95 [95% CI, 0.39 to 9.82; P=0.42]; 0.44 [95% CI, 0.05 to 3.72; P=0.45]; and 1.34 [95% CI, 0.20 to 8.82; P=0.76], respectively). At protocol-specified biopsy time points, the resistive index was not associated with renal-allograft histologic features. Older recipient age was the strongest determinant of a higher resistive index (P<0.001). At the time of biopsies performed because of graft dysfunction, antibody-mediated rejection or acute tubular necrosis, as compared with normal biopsy results, was associated with a higher resistive index (0.87 ± 0.12 vs. 0.78 ± 0.14 [P=0.05], and 0.86 ± 0.09 vs. 0.78 ± 0.14 [P=0.007], respectively).

CONCLUSIONS

The resistive index, routinely measured at predefined time points after transplantation, reflects characteristics of the recipient but not those of the graft. (ClinicalTrials.gov number, NCT01879124 .).

Relationship between retinal blood flow and renal function in patients with type 2 diabetes and chronic kidney disease

OBJECTIVE

To study the relationship between retinal microcirculation and renal function in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Using a laser Doppler velocimetry system, we obtained the retinal blood flow (RBF) values by simultaneously measuring the retinal vessel diameter and blood velocity. To determine if the RBF is affected in the presence of renal dysfunction, we also evaluated the renal function using the estimated glomerular filtration rate calculated by age and serum creatinine level.

RESULTS

We recruited 169 eyes of 169 consecutive Japanese patients with type 2 diabetes, no or minimal diabetic retinopathy, and normo/microalbuminuria (mean age ± SD, 59.0 ± 11.1 years). We divided the patients into four groups based on the stage of chronic kidney disease (CKD) (non-CKD, n = 99; CKD stage 1, n = 22; stage 2, n = 27; stage 3, n = 21). We found significant (P = 0.035) decreases in RBF with decreased vessel diameter (P = 0.017) but no difference in blood velocity (P = 0.54) in stage 3 CKD compared with the non-CKD group. Multiple regression analysis showed that the CKD stage was significantly (P = 0.02) and independently associated with decreased RBF.

CONCLUSIONS

Our results indicated that the vessel diameter and RBF in the retinal arterioles decrease in patients with type 2 diabetes with stage 3 CKD, suggesting that impaired renal function might be associated with decreased RBF, probably via constriction of the retinal arterioles, in early-phase diabetic retinopathy.

Intrarenal arterial resistance is associated with microvascular complications in Chinese type 2 diabetic patients

BACKGROUND

Increased renal arterial resistance is associated with various types of chronic renal parenchymal diseases. A resistance index (RI) > 0.8 predicts deterioration in renal function in diabetic subjects. However, the association between renal RI and other diabetic complications has not been investigated. In this study, we examined the association between intrarenal arterial RI and diabetic complications in Chinese type 2 diabetic subjects.

METHODS

Three hundred and eighty-seven Chinese type 2 diabetic patients were recruited from a structured assessment programme to evaluate their risk factors and complications as a part of the quality improvement programme at the Prince of Wales Hospital. All subjects underwent ultrasound examinations for the assessment of intrarenal arterial RI of both kidneys. Clinical and biochemical parameters, including diabetes-related microvascular complications (nephropathy, retinopathy and sensory neuropathy) and macrovascular diseases, were examined.

RESULTS

The mean RI of patients with any microvascular complications (0.70 ± 0.09 versus 0.65 ± 0.06) such as nephropathy (0.71 ± 0.09 versus 0.66 ± 0.06), retinopathy (0.71 ± 0.08 versus 0.67 ± 0.08) and sensory neuropathy (0.75 ± 0.07 versus 0.68 ± 0.08) and with any macrovascular complications (0.71 ± 0.09 versus 0.68 ± 0.08) was higher than those without (P < 0.05). On multivariate analysis, after controlling for confounding variables, an RI ≥0.75 was associated with microvascular complications, nephropathy, retinopathy and sensory neuropathy, with odds ratio of 4.02 [95% confidence interval (CI) 1.72-9.4], 4.99 (2.61-9.56), 2.78 (1.52-5.09) and 5.74 (1.8-18.3), respectively. The association of RI with macrovascular complications was not significant in multivariate analysis.

CONCLUSION

Increased intrarenal arterial resistance was independently associated with an increased risk of microvascular complications including diabetic nephropathy, diabetic retinopathy and diabetic sensory neuropathy in Chinese type 2 diabetic patients.

Renal Resistive Index and Cardiovascular and Renal Outcomes in Essential Hypertension

Increased renal restive index (RI) measured using Doppler ultrasonography has been shown to correlate with the degree of renal impairment in hypertensive patients. We investigated the prognostic role of RI in cardiovascular and renal outcomes. A total of 426 essential hypertensive subjects (mean age, 63 years; 50% female) with no previous cardiovascular disease were included in this study. Renal segmental arterial RI was measured by duplex Doppler ultrasonography. During follow-up (mean, 3.1 years), 57 participants developed the primary composite end points including cardiovascular and renal outcomes. In multivariate Cox regression analysis, RI was an independent predictor of worse outcome in total subjects (hazard ratio, 1.71 for 1 SD increase), as well as in patients with estimated glomerular filtration rate (eGFR) <60 mL/min per 1.73 m 2 (hazard ratio, 2.11 for 1 SD increase; P <0.01, respectively). When divided into 4 groups based on the respective sex-specific median levels of RI in the eGFR ≥60 and eGFR <60 mL/min per 1.73 m 2 groups, the group with eGFR <60 and high RI (male ≥0.73, female ≥0.72) had a significantly poorer event-free survival rate (χ 2 =126.4; P <0.01), and the adjusted hazard ratio by multivariate Cox regression analysis was 9.58 (95% CI, 3.26–32.89; P <0.01). In conclusion, impairment of renal hemodynamics evaluated by increased RI is associated with an increased risk of primary composite end points, and the combination of high RI and low eGFR is a powerful predictor of these diseases in essential hypertension. In hypertensive patients with chronic kidney disease, RI evaluation may complement predictors of cardiovascular and renal outcomes.

Correlation between the resistive index values of renal and orbital arteries

BACKGROUND

Resistive index (RI) is an indirect measurement of blood flow resistance that can be used to evaluate vascular damage.

AIMS

The purpose of this study is to evaluate the association between RI values of orbital and intrarenal arteries by means of Doppler ultrasonography (US).

METHODS

We evaluated 103 diabetic patients. As a control group, 30 subjects were examined. The patients were divided into two groups. Group 1 consisted of patients with urinary albumin excretion (UAE) <300 mg/day and estimated glomerular filtration rate (eGFR) levels >90 ml/min (n = 50); Group 2 had a UAE >300 mg/day and/or eGFR levels between 89 and 60 ml/min (n = 53). The association between RI values obtained with Doppler US of the ophthalmic artery, central retinal artery, posterior ciliary artery and intrarenal arteries were calculated.

RESULTS

Both orbital and intrarenal arterial RI values in Group 1 and Group 2 were higher than the control group (p = 0.001); furthermore, values were higher in Group 2 than in Group 1 (p = 0.0004/0.029/0.036, p = 0.016, respectively). A positive correlation was found between orbital and intrarenal arterial RI values in Group 2 (r = 0.475, 0.285, 0.363, p < 0.01, respectively).

CONCLUSION

Both orbital and renal arterial RI values were shown to be higher than the control group. Further, a trend towards higher RI values was observed with renal disease. RI may be useful as one of the markers for early diagnosis and follow-up of diabetic nephropathy and retinopathy.

Central pulse pressure and aortic stiffness determine renal hemodynamics: pathophysiological implication for microalbuminuria in hypertension

A significant link has been reported between aortic stiffening and renal microvascular damage, but the underlying mechanism remains poorly understood. We hypothesized that alterations in central and renal hemodynamics are responsible for this link. In 133 patients with hypertension, pressure waveforms were recorded on the radial, carotid, femoral, and dorsalis pedis arteries with applanation tonometry to estimate the aortic pressures and aortic (carotid-femoral) and peripheral (carotid-radial and femoral-dorsalis pedis) pulse wave velocities. Flow-velocity waveforms were recorded on the renal segmental arteries with duplex ultrasound to calculate the resistive index (RI) as [1 - (end-diastolic velocity/peak systolic velocity)] and on the femoral arteries to calculate the reverse/forward flow index and diastolic/systolic forward-flow ratio. Albuminuria was defined as urinary albumin/creatinine ratio ≥30 mg/g of creatinine. The renal RI (mean: 0.65±0.07) was strongly correlated (P<0.001) with the aortic pulse pressure (r=0.62), incident pressure wave (r=0.55), augmented pressure (r=0.49), and aortic pulse wave velocity (r=0.51), although not with the mean arterial pressure or peripheral pulse wave velocities. The correlations remained highly significant after consideration of confounders including age, cholesterol, hemoglobin A(1c), and glomerular filtration rate. The renal RI was inversely correlated with the femoral reverse and diastolic forward flow indices. Both aortic pulse pressure and renal RI correlated with the urinary albumin/creatinine ratio independent of confounders. Each 0.1 increase in renal RI was associated with a 5.4-fold increase in the adjusted relative risk of albuminuria. In conclusion, increased aortic pulse pressure causes renal microvascular damage through altered renal hemodynamics resulting from increased peripheral resistance and/or increased flow pulsation.

New approaches for the evaluation of renal vascular function in diabetes

In this issue of Diabetologia, two new approaches are described for the assessment of intra-renal blood flow in people with diabetes. The first approach used the technique of dynamic assessment of the resistance index (RI) in the renal interlobar arteries before and after administration of sublingual glyceryl trinitrate, and the second used MRI to assess total renal blood flow in relation to mean arterial pressure, thereby enabling direct measurement of overall renal RI. The results of the first study raise the possibility that dynamic evaluation of the intra-renal RI could be used as an early detector of vascular alterations in type 2 diabetes, before the onset of microalbuminuria. The results of the second study suggest that decreases in renal blood flow in people with longstanding type 1 diabetes reflect intra-renal vascular stiffening and raise the possibility that in microalbuminuric patients it may also reflect increased intraglomerular pressure.

Associations of intra-renal arterial resistance index with chronic kidney disease and carotid intima-media thickness in type 2 diabetes mellitus

Renal dysfunction can be evaluated by increased intra-renal arterial resistance index (RI). We evaluated 113 Chinese men with type 2 diabetes on their RI. Results suggest that RI is associated with chronic kidney disease and subclinical arteriosclerosis. RI may help monitoring the deterioration of intra-renal hemodynamics.

Renal resistance index and its prognostic significance in patients with heart failure with preserved ejection fraction

BACKGROUND

Functional renal impairment is a common feature of heart failure with preserved ejection fraction (HFpEF). The link between functional renal impairment and HFpEF remains incompletely understood. With hypertension and diabetes as frequent co-morbidities, patients with HFpEF are at risk of developing intra-renal vascular hemodynamic alterations that may lead to functional renal impairment and impact on prognosis.

METHODS

Renal resistive index (RRI) was non-invasively determined by Doppler ultrasonic examination in 90 HFpEF patients and 90 age- and sex-matched hypertensive patients without evidence of heart failure (HF) who served as controls. Clinical, laboratory and cardiac echocardiography data were obtained in HFpEF patients and controls. To investigate its possible clinical relevance, RRI was evaluated as a prognostic index of all-cause mortality and hospitalization for HF.

RESULTS

Mean RRI was substantially greater in HFpEF patients than in controls (P < 0.0001), while mean blood pressure, glomerular filtration rate, hemoglobin and serum protein levels were significantly lower in HFpEF patients than in controls. On multivariable analysis, mean RRI was independently associated with HFpEF. In addition, increased mean RRI was an independent predictor of poor outcome [hazard ratio = 1.06 95% confidence interval (1.01-1.10), P = 0.007] and remained significantly associated with the outcome after adjustment for univariate predictors that included low mean blood pressure, low hemoglobin concentration and low glomerular filtration rate. Conclusion. Patients with HFpEF exhibit intra-renal vascular hemodynamic alterations. The severity of intra-renal vascular hemodynamic alterations correlates with a poor outcome.

Role of oxidized low density lipoproteins and free fatty acids in the pathogenesis of glomerulopathy and tubulointerstitial lesions in type 2 diabetes

Oxidized lipids initiate and modulate the inflammatory cellular events in the arterial wall and the formation of macrophage foam cells. CD36 mediates the cellular uptake of ox-LDL through its recognition of specific truncated fatty acid moieties and oxidized phosphatidylcholine. Evidence has been reported that chemokine CXCL16, rather than CD36, is the main scavenger receptor in human podocytes mediating the uptake of ox-LDL. Ox-LDL induces loss of nephrin expression from cultured podocytes. It has been recently shown that nephrin once phosphorilated associates with PI3K and stimulates the Akt dependent signaling. This pathway plays a critical role in nephrin-actin-dependent cytoskeleton activation and remodeling, in the control of protein trafficking and in podocyte survival. An enhanced FFA uptake by podocytes is mediated by increased C36 scavenger receptor expression, together with a decrease of betaoxidation and in turn intracellular lipid accumulation. Accumulated FFA that is trapped into the mitochondrial matrix leads to mitochondrial ROS production, lipid peroxidation and mitochondrial damage and dysfunction. A disturbed transport and oxidation of FFA, paralleled by an impaired antioxidant response, damages podocyte structure and leads to glomerulopathy in early stages of nephrosis. Increased triglyceride synthesis and ox-and glycated LDL uptake by mesangial cells may also contribute to determine diabetic glomerulopathy. Oxidative processes are pivotal events in injury to renal tubular and epithelial cells exposed to ox-LDL. Notably CXCL16 are the main receptors for the uptake of ox-LDL in podocytes, whereas CD36 plays this role in tubular renal cells. In overt type 2 diabetes Ox-LDL and FFA damage podocyte function, SD-podocyte structure and tubulointerstitial tissue, at least partially, through different pathogenetic mechanisms. Further studies are needed to investigate the role of Ox-LDL and FFA on renal complications in obese, insulin resistant patients before the development of diabetes. The aim of the present review is to briefly elucidate the patterns of systemic lipid metabolism and the individual effects of lipotoxicity at glomerular and tubular level in the kidney of overt type 2 diabetic patients. These findings better elucidate our knowledge of diabetic glomerulopathy, beside and along with previous findings, in vivo and in vitro, on ox-LDL and FFA effects in mesangial cells.

Renal Doppler indices in diabetic children with insulin resistance syndrome

End-stage renal failure is still a leading cause of mortality among type 1 diabetes patients. Insulin resistance plays a larger role in type 1 diabetes disease process than is commonly recognized. Detection of diabetic nephropathy as early as possible currently offers the best chance of delaying or possibly preventing progression to end-stage disease. Renal resistive index (RI) and pulsatility index (PI), measured using renal Doppler ultrasonography, reflect intrarenal vascular resistance. The present work aimed at examining renal Doppler indices (RI and PI) in type 1 diabetic children and their relation to features of insulin resistance and other established parameters of early diabetic nephropathy as microalbuminuria. One hundred diabetic children with a mean age of 13.4 ± 2.9 yr and an average diabetes duration of (7.2 ± 2.5 yr) were included. Thirty healthy children served as controls. All renal Doppler indices were significantly higher in children with type 1 diabetes mellitus (p ≤ 0.01). The worst parameters were observed in children diagnosed with insulin resistance syndrome (IRS) (38%), hypertensive (12%), and obese (4%) children. Resistive index showed a significant correlation to blood pressure (r = 0.2, p = 0.04), waist-hip ratio (r = 0.5, p = 0.02), insulin dose (r = 0.2, p = 0.02) and estimated glucose disposal rate (r = -0.5, p = 0.01). No correlation was noted to microalbuminuria, HbA1c, or duration of diabetes. The present work concluded that renal Doppler indices are worse in diabetic children and particularly those with IRS. These children appear to be at graver risk for diabetic nephropathy. In these patients adding renal Doppler assessment to their work up, might diagnose diabetic nephropathy at a prealbuminuric stage.