Contrast agent--associated nephrotoxicity

Revolutionizing lymph node metastasis imaging: the role of drug delivery systems and future perspectives

The deployment of imaging examinations has evolved into a robust approach for the diagnosis of lymph node metastasis (LNM). The advancement of technology, coupled with the introduction of innovative imaging drugs, has led to the incorporation of an increasingly diverse array of imaging techniques into clinical practice. Nonetheless, conventional methods of administering imaging agents persist in presenting certain drawbacks and side effects. The employment of controlled drug delivery systems (DDSs) as a conduit for transporting imaging agents offers a promising solution to ameliorate these limitations intrinsic to metastatic lymph node (LN) imaging, thereby augmenting diagnostic precision. Within the scope of this review, we elucidate the historical context of LN imaging and encapsulate the frequently employed DDSs in conjunction with a variety of imaging techniques, specifically for metastatic LN imaging. Moreover, we engage in a discourse on the conceptualization and practical application of fusing diagnosis and treatment by employing DDSs. Finally, we venture into prospective applications of DDSs in the realm of LNM imaging and share our perspective on the potential trajectory of DDS development.

Case report: Application of nonsurgical method in saving transplant renal vein thrombosis caused by acute diarrhea

Transplant renal vein thrombosis is a rare complication after kidney transplantation, which can seriously threaten graft survival. Though the measures like thrombolytic therapy or operative intervention could be taken to deal with this complication, allograft loss is the most common outcome. Thus, early finding as well as decisive intervention is crucial to saving the graft. Here we present a 46-year-old male patient who underwent kidney transplantation from a cadaveric donor who developed a transplant renal venous thrombosis induced by acute diarrhea more than 1 year after renal transplantation with an initial symptom of sudden anuria and pain in the graft area. Subsequently, serum creatinine levels increased to 810.0 μmol/L. Pelvic CT showed increased vascular density of the transplanted kidney, and contrast-enhanced ultrasound confirmed venous thrombosis. The patient was treated with heparin sodium alone and diuresis gradually resumed. After more than 1 year of follow-up, serum creatinine returned to the baseline level prior to thrombosis. Our case indicates that quick ancillary examination and treatment without hesitation would be indispensable in rescuing allografts with renal vein thrombus. Unfractionated heparin can be recommended as an effective treatment for mid-long-term renal transplantation patients with renal vein thrombosis.

Feasibility of contrast-enhanced ultrasonography (CEUS) in evaluating renal microvascular perfusion in pediatric patients

Background

Changes in renal microvascular perfusion are involved in several kidney diseases. Contrast-enhanced ultrasonography (CEUS) quantitative analysis can enable the estimation of renal microvascular perfusion non-invasively. However, to date, few pediatric patients with renal disease have been subjected to CEUS quantitative analysis. This study aimed to explore the feasibility of CEUS in evaluating renal microvascular perfusion in pediatric patients and paving its way to clinical practice.

Methods

Seventeen pediatric patients with chronic kidney disease (CKD) and five children without kidney disease were consecutively examined using CEUS. Quantitative analysis of CEUS images based on time-intensity curve (TIC) fittings was performed using specialized software. Quantitative parameters of wash-in microvascular blood flow, including A, k, B, and TtoPk, were generated from three regions of interest (ROIs) each in the cortex and medulla of each kidney.

Results

CEUS was performed in all children successfully and safely without the use of sedatives. All parameters (A, B, k, and TtoPk) demonstrated no statistical differences among the three sampling ROIs in the renal cortex and medulla. All parameters (A, B, k, and TtoPk) showed no statistical differences between the left and right sides of kidneys both in cortices and medullas. Comparing with patients with CKD stage 3–5, both control group and patients with CKD stage 1–2 had significantly higher values of parameter A in the renal cortex (p = 0.025 and p = 0.031, respectively). In control group and patients stage 1–2, the values of parameters k in the renal cortices were significantly higher than that in the renal medullas, while in patients with CKD stage 3–5, parameter k showed no statistically significant differences between the renal cortex and medulla (p = 0.173).

Conclusion

CEUS is safe and practicable in pediatric patients with chronic kidney disease. Renal microvascular perfusion estimated by CEUS could be a robust approach in the evaluation of pediatric renal diseases. Parameters A and k derived from CEUS quantitative analysis can provide great potential in non-invasive assessment of renal microvascular perfusion impairment in pediatric CKD.

Impact of machine-learning-based coronary computed tomography angiography-derived fractional flow reserve on decision-making in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

OBJECTIVES

To evaluate feasibility and diagnostic performance of coronary CT angiography (CCTA)-derived fractional flow reserve (CT-FFR) for detection of significant coronary artery disease (CAD) and decision-making in patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR) to potentially avoid additional pre-TAVR invasive coronary angiography (ICA).

METHODS

Consecutive patients with severe AS (n = 95, 78.6 ± 8.8 years, 53% female) undergoing pre-procedural TAVR-CT followed by ICA with quantitative coronary angiography were retrospectively analyzed. CCTA datasets were evaluated using CAD Reporting and Data System (CAD-RADS) classification. CT-FFR measurements were computed using an on-site machine-learning algorithm. A combined algorithm was developed for decision-making to determine if ICA is needed based on pre-TAVR CCTA: [1] all patients with CAD-RADS ≥ 4 are referred for ICA; [2] patients with CAD-RADS 2 and 3 are evaluated utilizing CT-FFR and sent to ICA if CT-FFR ≤ 0.80; [3] patients with CAD-RADS < 2 or CAD-RADS 2-3 and normal CT-FFR are not referred for ICA.

RESULTS

Twelve patients (13%) had significant CAD (≥ 70% stenosis) on ICA and were treated with PCI. Twenty-eight patients (30%) showed CT-FFR ≤ 0.80 and 24 (86%) of those were reported to have a maximum stenosis ≥ 50% during ICA. Using the proposed algorithm, significant CAD could be identified with a sensitivity, specificity, and positive and negative predictive value of 100%, 78%, 40%, and 100%, respectively, potentially decreasing the number of necessary ICAs by 65 (68%).

CONCLUSION

Combination of CT-FFR and CAD-RADS is able to identify significant CAD pre-TAVR and bears potential to significantly reduce the number of needed ICAs.

KEY POINTS

• Coronary CT angiography-derived fractional flow reserve (CT-FFR) using machine learning together with the CAD Reporting and Data System (CAD-RADS) classification safely identifies significant coronary artery disease based on quantitative coronary angiography in patients prior to transcatheter aortic valve replacement. • The combination of CT-FFR and CAD-RADS enables decision-making and bears the potential to significantly reduce the number of needed invasive coronary angiographies.

A Review of Clinical Applications for Super-resolution Ultrasound Localization Microscopy

Microvascular structure and hemodynamics are important indicators for the diagnosis and assessment of many diseases and pathologies. The structural and functional imaging of tissue microvasculature in vivo is a clinically significant objective for the development of many imaging modalities. Contrast-enhanced ultrasound (CEUS) is a popular clinical tool for characterizing tissue microvasculature, due to the moderate cost, wide accessibility, and absence of ionizing radiation of ultrasound. However, in practice, it remains challenging to demonstrate microvasculature using CEUS, due to the resolution limit of conventional ultrasound imaging. In addition, the quantification of tissue perfusion by CEUS remains hindered by high operator-dependency and poor reproducibility. Inspired by super-resolution optical microscopy, super-resolution ultrasound localization microscopy (ULM) was recently developed. ULM uses the same ultrasound contrast agent (i.e. microbubbles) in CEUS. However, different from CEUS, ULM uses the location of the microbubbles to construct images, instead of using the backscattering intensity of microbubbles. Hence, ULM overcomes the classic compromise between imaging resolution and penetration, allowing for the visualization of capillary-scale microvasculature deep within tissues. To date, many in vivo ULM results have been reported, including both animal (kidney, brain, spinal cord, xenografted tumor, and ear) and human studies (prostate, tibialis anterior muscle, and breast cancer tumors). Furthermore, a variety of useful biomarkers have been derived from using ULM for different preclinical and clinical applications. Due to the high spatial resolution and accurate blood flow speed estimation (approximately 1 mm/s to several cm/s), ULM presents as an enticing alternative to CEUS for characterizing tissue microvasculature in vivo. This review summarizes the principles and present applications of CEUS and ULM, and discusses areas where ULM can potentially provide a better alternative to CEUS in clinical practice and areas where ULM may not be a better alternative. The objective of the study is to provide clinicians with an up-to-date review of ULM technology, and a practical guide for implementing ULM in clinical research and practice.

Predictive value of plasma volume status for contrast-induced nephropathy in patients with heart failure undergoing PCI

AIMS

Contrast-induced nephropathy remains a common complication of coronary procedure and increases poor outcomes, especially in patients with heart failure. Plasma volume expansion relates to worsening prognosis of heart failure. We hypothesized that calculated plasma volume status (PVS) might provide predictive utility for contrast-induced nephropathy in patients with heart failure undergoing elective percutaneous coronary intervention (PCI).

METHODS AND RESULTS

We enrolled 441 patients with heart failure undergoing elective PCI from 2012 to 2018. Pre-procedural estimated PVS by the Duarte's formula (Duarte-ePVS) and Kaplan-Hakim formula (KH-ePVS) were calculated for all patients. CIN was defined as an absolute serum creatinine (SCr) increase ≥0.5 mg/dL or a relative increase ≥25% compared with the baseline value within 48 h of contrast medium exposure. We assessed the association between PVS and CIN in patients with heart failure undergoing elective PCI. In 441 patients, 28 (6.3%) patients developed CIN. The median Duarte-ePVS was 4.44 (3.87, 5.13) and the median KH-ePVS was -0.03 (-0.09, 0.05). The best cutoff values for Duarte-ePVS and KH-ePVS to predict CIN were 4.64 (with 78.6% sensitivity and 61.7% specificity) and 0.04 (with 64.5% sensitivity and 75.5% specificity), respectively. After adjusting for potential confounding variables, KH-ePVS > 0.04 [odds ratio (OR) 2.685, 95% confidence interval (CI) 1.012-7.123, P = 0.047] remained significantly associated with CIN whereas Duarte-ePVS was not.

CONCLUSIONS

Pre-procedural KH-ePVS is an independent risk factor for CIN in patients with heart failure undergoing elective PCI. The best cutoff point of KH-ePVS for predicting CIN was 0.04.

Acute Renal Failure/Acute Kidney Injury (AKI) Associated with Endovascular Procedures

AKI is one of the most common yet underdiagnosed postoperative complications that can occur after any type of surgery. Contrast-induced nephropathy (CIN) is still poorly defined and due to a wide range of confounding individual variables, its risk is difficult to determine. CIN mainly affects patients with underlying chronic kidney disease, diabetes, sepsis, heart failure, acute coronary syndrome and cardiogenic shock. Further research is necessary to better understand pathophysiology of contrast-induced AKI and consequent implementation of effective prevention and therapeutic strategies. Although many therapies have been tested to avoid CIN, the only potent preventative strategy involves aggressive fluid administration and reduction of contrast volume. Regardless of surgical technique—open or endovascular—perioperative AKI is associated with significant morbidity, mortality and cost. Endovascular procedures always require administration of a contrast media, which may cause acute tubular necrosis or renal vascular embolization leading to renal ischemia and as a consequence, contribute to increased number of post-operative AKIs.

Carbon dioxide-angiography for patients with peripheral arterial disease at risk of contrast-induced nephropathy

Patients with peripheral arterial disease (PAD) and critical limb ischemia are at risk for limb amputation and require urgent management to restore blood flow. Patients with PAD often have several comorbidities, including chronic kidney disease, diabetes mellitus, and hypertension. Diagnostic and interventional angiography using iodinated contrast agents provides excellent image resolution but can be associated with contrast-induced nephropathy (CIN). The use of carbon dioxide (CO₂) as a contrast agent reduces the volume of iodine contrast required for angiography and reduces the incidence of CIN. However, CO₂ angiography has been underutilized due to concerns regarding safety and image quality. Modern CO₂ delivery systems with advanced digital subtraction angiography techniques and hybrid angiography have improved imaging accuracy and reduced the incidence of CIN. Awareness of the need for optimal imaging conditions, contraindications, and potential complications have improved the safety of CO₂ angiography. This review aims to highlight current technological advances in the delivery of CO₂ in vascular angiography for patients with PAD and critical limb ischemia, which result in limb preservation while preventing kidney damage.

The Effect of Contrast Administration on Renal Function after Cardiac Catheterization in Saudi Patients

Background:

The increase of serum creatinine by 25% from the baseline readings will lead to contrast-induced nephropathy. Most of the time this acute reduction in kidney function will occur in the first 48 h after angiogram; diabetes mellitus (DM) is one of the major predisposing factors.

Objectives:

Our objective is to study the influence of contrast material administration during angiogram on kidney function, especially in patients with risk factors such as DM in the Saudi community.

Methods:

This was an open-label study; we included 1250 patients from July 2010 to June 2011, and we studied all comers during that period; more than 60% of admissions came through the emergency department with acute coronary syndrome, in addition to elective admission with stable computer-aided design.

Results:

The incidence of nephropathy related to the contrast used during angiogram was 4.8%, and this represents 60 patients of 1250. Of the 60 patients, the number of diabetic patients who developed nephropathy was 37 (62%). 40 (67%) patients were hypertensive. Twenty-five (42%) patients had body weight <70 kg, 37 (62%) had diagnostic cath, 23 (38%) underwent percutaneous coronary intervention, and 47 (78%) received Omnipaque contrast media.

Conclusion:

The incidence of nephropathy postcoronary angiogram was 4.8%; the two major risk factors in our Saudi patients were hypertension and diabetes; the diabetic patients should be monitored precisely, and special measures should be taken seriously.

Optimal frequency of scans for patients on cancer therapies: A population kinetics assessment

Background

Optimal frequency of follow‐up scans for patients receiving systemic therapies is poorly defined. Progression‐free survival (PFS) generally follows first‐order kinetics. We used exponential decay nonlinear regression analysis to calculate half‐lives for 887 published PFS curves.

Method

We used the Excel formula x = EXP(‐t_n*0.693/t_1/2) to calculate proportion of residual patients remaining progression‐free at different times, where t_n is the interval in weeks between scans (eg, 6 weeks), * indicates multiplication, 0.693 is the natural logarithm of 2, and t_1/2 is the PFS half‐life in weeks.

Results

Proportion of residual patients predicted to remain progression‐free at each subsequent scan varied with scan intervals and regimen PFS half‐life. For example, with a 4‐month half‐life (17.3 weeks) and scans every 6 weeks, 21% of patients would progress by the first scan, 21% of the remaining patients would progress by the second scan at 12 weeks, etc With 2, 6‐ and 12‐month half‐lives (for example), the proportion of remaining patients progressing at each subsequent scan if repeated every 3 weeks would be 21%, 8% and 4%, respectively, while with scans every 12 weeks it would be 62%, 27% and 15%, respectively. Furthermore, optimal scan frequency can be calculated for populations comprised of distinct rapidly and slowly progressing subpopulations, as well as with convex curves arising from treatment breaks, where optimal scan frequency may differ during therapy administration vs during more rapid progression after therapy interruption.

Conclusions

A population kinetics approach permits a regimen‐ and tumor‐specific determination of optimal scan frequency for patients on systemic therapies.

Biomedical Imaging: Principles, Technologies, Clinical Aspects, Contrast Agents, Limitations and Future Trends in Nanomedicines

This review article presents the state-of-the-art in the major imaging modalities supplying relevant information on patient health by real-time monitoring to establish an accurate diagnosis and potential treatment plan. We draw a comprehensive comparison between all imagers and ultimately end with our focus on two main types of scanners: X-ray CT and MRI scanners. Numerous types of imaging probes for both imaging techniques are described, as well as reviewing their strengths and limitations, thereby showing the current need for the development of new diagnostic contrast agents (CAs). The role of nanoparticles in the design of CAs is then extensively detailed, reviewed and discussed. We show how nanoparticulate agents should be promising alternatives to molecular ones and how they are already paving new routes in the field of nanomedicine.

Impact of aortic wall thrombus on late changes in renal function among patients treated by fenestrated-branched endografts

OBJECTIVE

Renal function deterioration is an important determinant of mortality in patients treated for complex aortic aneurysms. We have previously determined that catheter and guidewire manipulation in diseased aortas during fenestrated-branched endovascular aneurysm repair (F-BEVAR) is associated with risk of renal function deterioration. The aim of this study was to describe the impact of atherothrombotic aortic wall thrombus (AWT) on renal function deterioration among patients treated by F-BEVAR for pararenal and extent IV thoracoabdominal aortic aneurysms.

METHODS

Clinical data of 212 patients treated for complex aortic aneurysms with F-BEVAR were entered into a prospectively maintained database (2007-2015). AWT was evaluated by computed tomography angiography using volumetric measurements in nonaneurysmal aortic segments. AWT was classified as mild, moderate, or severe using objective assessment of the number of affected segments, thrombus type, thickness, area, and circumference. Acute kidney injury (AKI) was defined using Risk, Injury, Failure, Loss of kidney function, and End-stage renal disease (RIFLE) criteria, and renal function deterioration was defined by a decline in estimated glomerular filtration rate (eGFR) >30% from baseline. Patient survival and renal outcomes were assessed at dismissal, at 6 to 8 weeks, at 6 months, and annually, including AKI, serum creatinine concentration, eGFR, chronic kidney disease stage, need for renal replacement therapy, and presence of kidney infarction.

RESULTS

There were 169 male (80%) and 43 female (20%) patients with a mean age of 75 ± 7 years. Aneurysm extent was pararenal in 157 patients and extent IV thoracoabdominal aortic aneurysm in 55 patients. A total of 700 renal-mesenteric arteries were incorporated (3.1 ± 1 vessels/patient). AWT was classified as mild in 98 patients (46%), moderate in 75 (35%), and severe in 39 (19%). At 30 days, 45 patients (21%) developed AKI. Decline in eGFR and kidney infarction were associated with higher AWT volume index and severe AWT classification (P < .05). There was no association of AWT with 30-day mortality, which was 0.5% for the entire cohort. Mean follow-up was 29 ± 23 months. Freedom from renal function deterioration was 73% ± 6% for mild, 81% ± 6% for moderate, and 66% ± 8% for severe AWT patients at 3 years (P = .012) and 46% ± 9% and 82% ± 4% for those with or without AKI after the initial procedure (P < .001). Overall, 41 patients (19%) had progression of chronic kidney disease stage, but none of the patients required renal replacement therapy. Survival was 73% ± 5% for mild, 72% ± 6% for moderate, and 69% ± 10% for severe AWT patients at 3 years (P = .67).

CONCLUSIONS

AWT is a significant predictor of AKI and continued decline in renal function after the initial F-BEVAR procedure. Longer follow-up time is needed to determine the actual impact of AWT on survival.

In situ lactate dehydrogenase activity: a novel renal cortical imaging biomarker of tubular injury?

Renal ischemia-reperfusion injury is the state of which a tissue experiences injury after a phase of restrictive blood supply and recirculation. Ischemia-reperfusion injury (I/R-I) is a leading cause of acute kidney injury (AKI) in several disease states, including kidney transplantation, sepsis, and hypovolemic shock. The most common methods to evaluate AKI are creatinine clearance, plasma creatinine, blood urea nitrogen, or renal histology. However, currently, there are no precise methods to directly assess renal injury state noninvasively. Hyperpolarized 13C-pyruvate MRI enables noninvasive accurate quantification of the in vivo conversion of pyruvate to lactate, alanine, and bicarbonate. In the present study, we investigated the in situ alterations of metabolic conversion of pyruvate to lactate, alanine, and bicarbonate in a unilateral I/R-I rat model with 30 min and 60 min of ischemia followed by 24 h of reperfusion. The pyruvate conversion was unaltered compared with sham in the 30 min I/R-I group, while a significant reduced metabolic conversion was found in the postischemic kidney after 60 min of ischemia. This indicates that after 30 min of ischemia, the kidney maintains normal metabolic function in spite of decreased kidney function, whereas the postischemic kidney after 60 min of ischemia show a generally reduced metabolic enzyme activity concomitant with a reduced kidney function. We have confidence that these findings can have a high prognostic value in prediction of kidney injury and the outcome of renal injury.

Expression of neutrophil gelatinase-associated lipocalin in low osmolar contrast-induced nephropathy in rats and the effect of N-acetylcysteine

Serum creatinine (Scr), which is a conventional indicator of contrast-induced nephropathy (CIN), is unable to reflect the damage of kidney promptly. The present study aimed to investigate the value of neutrophil gelatinase-associated lipocalin (NGAL) in kidney and serum of CIN rats to observe whether NGAL can be used as a superior indicator of CIN. Furthermore, N-acetylcysteine (NAC) was used to assess its effect on CIN. A total of 120 adult male Sprague Dawley rats were randomly divided into four groups (n=30/group): CIN rats (CIN), normal rats treated with NAC (NAC), CIN rats treated with NAC (NAC+CIN) and the control group (CON). Serum Scr and NGAL values were measured at 2, 12, 24, 48 and 72 h following the procedure. Immunohistochemistry and western blot analysis were used to detect NGAL within the kidney tissue. Hematoxylin and eosin staining were used to access the renal injury score. Oxidative stress within the kidney was analyzed via malondialdehyde (MDA) and superoxide dismutase (SOD). The level of NGAL in the serum and tissue of the CIN group increased significantly 2 h after the procedure (P<0.05). However, the Scr value did not exhibit a significantly change until 48 h later. Based on the renal injury scores, NAC reduced the kidney damage caused by the contrast. NAC treatment was associated with a decrease in SOD levels and an increase in MDA. These findings suggested that NGAL was a superior indicator of CIN than Scr, as NGAL was able to detect kidney damage much earlier. Furthermore, NAC treatment inhibited oxidative stress, thus protecting against CIN.

Antioxidant and renoprotective effects of sphingosylphosphorylcholine on contrast-induced nephropathy in rats

Contrast induced nephropathy (CIN) is a major cause of morbidity, and increased costs as well as an increased risk of death. This study was evaluated effects of exogenous sphingosylphosphorylcholine (SPC) administration on CIN in rats. Eight animals were included in each of the following eight groups: control, control phosphate-buffered solution (PBS), control SPC 2, control SPC 10, CIN, CIN PBS, CIN SPC 2 and CIN SPC 10. The induced nephropathy was created by injected with 4 g iodine/kg body weight. SPC was administered 3 d at a daily two different doses of 2 μm/mL and 10 μm/mL intraperitoneally. The severity of renal injury score was determined by the histological and immunohistochemical changes in the kidney. Malondialdehyde (MDA), nitric oxide (NO) and superoxide dismutase (SOD) were determined to evaluate the oxidative status in the renal tissue. Treatment with 2 and 10 μM SPC inhibited the increase in renal MDA, NO levels significantly and also attenuated the depletion of SOD in the renal injuryCIN. These data were supported by histopathological findings. The inducible nitric oxide synthase positive cells and apoptotic cells in the renal tissue were observed to be reduced with the 2 and 10 μM SPC treatment. These findings suggested that 2 and 10 μM doses can attenuate renal damage in contrast nephropathy by prevention of oxidative stress and apoptosis. The low and high dose SPC may be a promising new therapeutic agent for CIN.

Real-time in vitro intravascular reconstruction and navigation for endovascular aortic stent grafting

BACKGROUND

Trans-catheter endovascular stent grafting minimizes trauma and increases the benefitting patient population. However, the alignment between stent graft branches and vasculature branches remains time-consuming and challenging, and such techniques require a significant amount of contrast agent for imaging.

METHODS

A new framework for intravascular reconstruction based on sensor fusion between intravascular ultrasound (IVUS) imaging and electromagnetic (EM) tracking was proposed. A new image processing method was presented to realize fully automatic processing of IVUS imaging and 3D reconstruction in real time, as well as branch detection for alignment and deployment. Complementary navigation using CT data allows for efficient catheter advancement and assistant clinical judgement.

RESULTS

The reconstruction of an in vitro descending aorta phantom with branches was realized at 35 Hz, with cross-section radius average error of 0.64 mm.

CONCLUSION

The proposed method demonstrates significant potential for clinical applications, enables navigation for precise alignment and placement for stent grafting to reduce surgical time, and decreases hemorrhagic collisions and the use of contrast agent. Copyright © 2016 John Wiley & Sons, Ltd.

Advantages and Limitations of Focal Liver Lesion Assessment with Ultrasound Contrast Agents: Comments on the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) Guidelines

Contrast-enhanced ultrasound (CEUS) represents a significant breakthrough in sonography. Due to US contrast agents (UCAs) and contrast-specific techniques, sonography offers the potential to show enhancement of liver lesions in a similar way as contrast-enhanced cross-sectional imaging techniques. The real-time assessment of liver perfusion throughout the vascular phases, without any risk of nephrotoxicity, represents one of the major advantages that this technique offers. CEUS has led to a dramatic improvement in the diagnostic accuracy of US and subsequently has been included in current guidelines as an important step in the diagnostic workup of focal liver lesions (FLLs), resulting in a better patient management and cost-effective therapy. The purpose of this review was to provide a detailed description of contrast agents used in different cross-sectional imaging procedures for the study of FLLs, focusing on characteristics, indications and advantages of UCAs in clinical practice.

Drug-Induced Nephrotoxicity and Dose Adjustment Recommendations: Agreement Among Four Drug Information Sources

Hospitalized patients require the use of a variety of drugs, many of which individually or in combination have the potential to cause kidney damage. The use of potentially nephrotoxic drugs is often unavoidable, and the need for dose adjustment should be evaluated. This study is aimed at assessing concordance in information on drug-induced nephrotoxicity and dose adjustment recommendations by comparing four drug information sources (DRUGDEX^®, UpToDate^®, Medscape^® and the Brazilian Therapeutic Formulary) using the formulary of a Brazilian public hospital. A total of 218 drugs were investigated. The global Fleiss’ kappa coefficient was 0.265 for nephrotoxicity (p < 0.001; CI 95%, 0.211–0.319) and 0.346 for recommendations (p < 0.001; CI 95%, 0.292–0.401), indicating fair concordance among the sources. Anti-infectives and anti-hypertensives were the main drugs cited as nephrotoxic by the different sources. There were no clear definitions for qualitative data or quantitative values for dose adjustments among the four information sources. There was no advice for dosing for a large number of the drugs in the international databases. The National Therapeutic Formulary offered imprecise dose adjustment recommendations for many nephrotoxic drugs. Discrepancies among information sources may have a clinical impact on patient care and contribute to drug-related morbidity and mortality.

Intravenous Imaging Contrast Media Complications: The Basics That Every Clinician Needs to Know

Intravenous contrast is commonly used in noninvasive imaging procedures such as magnetic resonance imaging and computed tomography and can evaluate blood vessels and better characterize soft-tissue lesions. Although the incidence of adverse events after administration of contrast is low, it is important that clinicians and radiologists minimize risks and respond quickly and effectively when reactions occur. We will discuss a range of adverse events to iodinated and gadolinium-based contrast agents, including allergic-like reactions, nephrotoxicity, extravasation, and nephrogenic systemic fibrosis. We will review risk stratification for patients, as well as premedication and treatment of adverse events.

Optimization of Contrast-to-Tissue Ratio Through Pulse Windowing in Dual-Frequency "Acoustic Angiography" Imaging

Early-stage tumors in many cancers are characterized by vascular remodeling, indicative of transformations in cell function. We have previously presented a high-resolution ultrasound imaging approach to detecting these changes that is based on microbubble contrast agents. In this technique, images are formed from only the higher harmonics of microbubble contrast agents, producing images of vasculature alone with 100- to 200-μm resolution. In this study, shaped transmit pulses were used to image the higher broadband harmonic echoes of microbubble contrast agents, and the effects of varying pulse window and phasing on microbubble and tissue harmonic echoes were evaluated using a dual-frequency transducer in vitro and in vivo. An increase in the contrast-to-tissue ratio of 6.8 ± 2.3 dB was observed in vitro using an inverted pulse with a cosine window relative to a non-inverted pulse with a rectangular window. The increase in mean image intensity resulting from contrast enhancement in vivo in five rodents was 13.9 ± 3.0 dB greater for an inverted cosine-windowed pulse and 17.8 ± 3.6 dB greater for a non-inverted Gaussian-windowed pulse relative to a non-inverted pulse with a rectangular window. Implications for pre-clinical and diagnostic imaging are discussed.

Contrast-Induced Nephropathy: Identifying the Risks, Choosing the Right Agent, and Reviewing Effective Prevention and Management Methods

With the rise in the use of intravenous iodinated contrast media for both computed tomography scan and angiographic studies, there is a greater likelihood of complications. One of the most well-known adverse effects is contrast-induced media nephropathy, which is also called contrast-induced acute kidney injury. This is third most common cause of hospital acquired acute renal failure. It is associated with an increase in morbidity, mortality, and greater financial burden on healthcare system. Because of these factors, it is important for the radiologist to not only recognize risk factors, as well as the signs and symptoms, but also to know how to manage patients appropriately.

Systemic and renal hemodynamic effects of intra-arterial radiocontrast

Background

Decreased renal blood flow (RBF) and vasoconstriction are considered major mechanisms of contrast-induced acute kidney injury (CIAKI). To understand the severity and duration of such putative effects, we measured systemic and renal hemodynamics after intra-arterial radiocontrast administration. The subjects were six Merino ewes. The setting was a university-affiliated research institute. This is a randomized cross-over experimental study.

Methods

Transit-time flow probes were implanted on the pulmonary and left renal arteries 2 weeks before experimentation. We simulated percutaneous coronary intervention by administering five intra-arterial boluses of 0.5 mL/kg saline (control) or radiocontrast (iodixanol) to a total of 2.5 mL/kg over 1 h. Cardiac output (CO), heart rate, mean arterial pressure (MAP), RBF, renal vascular conductance (RVC), urine output (UO), creatinine clearance (CrCl), and fractional excretion of sodium (FENa) were measured.

Results

In the first 8 h after intra-arterial administration of radiocontrast, CO, total peripheral conductance (TPC), and heart rate (HR) increased compared with those after normal saline administration. Thereafter, CO and TPC were similar between the two groups, but HR remained higher with radiocontrast (p < 0.001). After a short (30 min) period of renal vasoconstriction with preserved RBF secondary to an associated increase in MAP, RBF and RVC showed an earlier and greater increase (vasodilatation) with radiocontrast (p < 0.001) and remained higher during the first 2 days. Radiocontrast initially increased urine output (p < 0.001) and FENa (p = 0.003). However, the overall daily urine output decreased in the radiocontrast-treated animals at 2 days (p < 0.001) and 3 days (p = 0.006). Creatinine clearance was not affected.

Conclusions

In healthy animals, intra-arterial radiocontrast increased RBF, induced renal vasodilatation, and caused a delayed period of oliguria. Our findings suggest that sustained reduction in RBF and renal vasoconstriction may not occur in normal large mammals after intra-arterial radiocontrast administration.

Iodinated contrast media cause direct tubular cell damage, leading to oxidative stress, low nitric oxide, and impairment of tubuloglomerular feedback

Iodinated contrast media (CM) have adverse effects that may result in contrast-induced acute kidney injury. Oxidative stress is believed to play a role in CM-induced kidney injury. We test the hypothesis that oxidative stress and reduced nitric oxide in tubules are consequences of CM-induced direct cell damage and that increased local oxidative stress may increase tubuloglomerular feedback. Rat thick ascending limbs (TAL) were isolated and perfused. Superoxide and nitric oxide were quantified using fluorescence techniques. Cell death rate was estimated using propidium iodide and trypan blue. The function of macula densa and tubuloglomerular feedback responsiveness were measured in isolated, perfused juxtaglomerular apparatuses (JGA) of rabbits. The expression of genes related to oxidative stress and the activity of superoxide dismutase (SOD) were investigated in the renal medulla of rats that received CM. CM increased superoxide concentration and reduced nitric oxide bioavailability in TAL. Propidium iodide fluorescence and trypan blue uptake increased more in CM-perfused TAL than in controls, indicating increased rate of cell death. There were no marked acute changes in the expression of genes related to oxidative stress in medullary segments of Henle's loop. SOD activity did not differ between CM and control groups. The tubuloglomerular feedback in isolated JGA was increased by CM. Tubular cell damage and accompanying oxidative stress in our model are consequences of CM-induced direct cell damage, which also modifies the tubulovascular interaction at the macula densa, and may therefore contribute to disturbances of renal perfusion and filtration.

Comparison of effects of isotonic sodium chloride with diltiazem in prevention of contrast-induced nephropathy

INTRODUCTION AND OBJECTIVE

Contrast-induced nephropathy (CIN) significantly increases the morbidity and mortality of patients. The aim of this study is to investigate and compare the protective effects of isotonic sodium chloride with sodium bicarbonate infusion and isotonic sodium chloride infusion with diltiazem, a calcium channel blocker, in preventing CIN.

MATERIALS AND METHODS

Our study included patients who were administered 30-60 mL of iodinated contrast agent for percutaneous coronary angiography (PCAG), all with creatinine values between 1.1 and 3.1 mg/dL. Patients were divided into three groups and each group had 20 patients. The first group of patients was administered isotonic sodium chloride; the second group was administered a solution that of 5% dextrose and sodium bicarbonate, while the third group was administered isotonic sodium chloride before and after the contrast injection. The third group received an additional injection of diltiazem the day before and first 2 days after the contrast injection. All of the patients' plasma blood urea nitrogen (BUN) and creatinine levels were measured on the second and seventh day after the administration of intravenous contrast material.

RESULTS

The basal creatinine levels were similar for all three groups (p > 0.05). Among a total of 60 patients included in the study, 16 patients developed acute renal failure (ARF) on the second day after contrast material was injected (26.6%). The number of patients who developed ARF on the second day after the injection in the first group was five (25%), in the second group was six (30%) and the third group was five (25%) (p > 0.05).

CONCLUSION

There was no significant difference between isotonic sodium chloride, sodium bicarbonate and isotonic sodium chloride with diltiazem application in prevention of CIN.

[Incidence and clinical outcome of contrast-induced nephropathy in the elderly patients]

BACKGROUND

Aging is an established risk factor for contrast-induced nephropathy (CIN). However, little information is available on the incidence and clinical outcome of CIN for the elderly patients in Japan.

OBJECTIVES

We determined the incidence and clinical outcome of CIN in the Japanese elderly patient.

METHODS

We studied 292 patients who had mild renal dysfunction (estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2)) at baseline and underwent coronary angiography. Patients were divided into two groups base on their age: the elderly group (age ≥ 75, n=108) and the control group (age<75, n=184). CIN was defined as a 25% increase in serum creatinine or an increase in serum creatinine by>0.5 mg/dl above the baseline value at or within 2 days post procedure.

RESULTS

Patients in the elderly group had a higher incidence of CIN (14%) than those in the control group (9%). In patients who developed CIN, there was no significant difference between the two groups in baseline GFR and GFR on days 1, 2, 7 and 30 after the procedure. However, the relative increase in GFR above baseline on day 7 (-4.0 ± 6.1 vs -8.3 ± 8.0 ml/min P=0.096) and day 30 (1.5 ± 9.4 vs -10.1 ± 9.6 ml/min P=0.0017) in the elderly group was higher than that in the control group. Furthermore, death occurred in 3 patients in the elderly group (20%) whereas no patient died in the control group (P=0.092).

CONCLUSION

Aging (age ≥ 75) is a risk factor for CIN in Japanese. CIN in the elderly patients may be associated with prolonged renal dysfunction and poor prognosis.

Contrast material-induced nephrotoxicity and intravenous low-osmolality iodinated contrast material

PURPOSE

To determine whether intravenous low-osmolality iodinated contrast material is associated with post-computed tomography (CT) acute kidney injury (AKI).

MATERIALS AND METHODS

Institutional review board approval was obtained and patient consent waived for this HIPAA-compliant retrospective study. CT examinations performed over a 10-year period in adult inpatients with sufficient serum creatinine (SCr) data were identified. A one-to-one propensity-matched matched cohort analysis with multivariate analysis of effects was performed with post-CT AKI as the primary outcome measure (10,121 unenhanced and 10,121 intravenous contrast-enhanced CT examinations in 20,242 patients). Propensity matching was performed with respect to likelihood of patient receiving intravenous contrast material (36 tested covariates). The primary endpoint was post-CT AKI by using Acute Kidney Injury Network SCr criteria; the secondary endpoint was post-CT AKI by using traditional SCr criteria for contrast material-induced nephrotoxicity (CIN; SCr increase ≥0.5 mg/dL [44.20 μmol/L] or ≥25%). Multivariate subgroup threshold analysis was performed (SCr <1.5 [<132.60 μmol/L]; ≥1.5 to ≥2.0 mg/dL [≥132.60 to ≥176.80 μmol/L]) and adjusted for assigned propensity scores.

RESULTS

Intravenous low-osmolality iodinated contrast material had a significant effect on the development of post-CT AKI for patients with pre-CT SCr levels of 1.6 mg/dL (141.44 μmol/L) or greater (odds ratio, 1.45; 95% confidence interval [CI]: 1.11, 1.89;P = .007). This effect strengthened as pre-CT SCr increased. Patients with stable SCr less than 1.5 mg/dL (132.60 μmol/L) were not at risk for developing CIN (P = .25, power > 95%). Both endpoints demonstrated similar results (eg, SCr ≥1.6 mg/dL [141.44 μmol/L] by using traditional CIN criteria: odds ratio, 1.64; 95% CI: 1.18, 2.28; P = .003). Post-CT AKI was prevalent in both the unenhanced and contrast-enhanced CT subgroups, and it increased with increases in pre-CT SCr. Many risk factors contributed to development of post-CT AKI, regardless of iodinated contrast material.

CONCLUSION

Intravenous low-osmolality iodinated contrast material is a nephrotoxic risk factor, but not in patients with a stable SCr level less than 1.5 mg/dL. Many factors other than contrast material can affect post-CT AKI rates.

Oral prostaglandin e1 in combination with sodium bicarbonate and normal saline in the prevention of contrast-induced nephropathy: a pilot study

The purpose of this study was to evaluate the use of prostaglandin E1 (PGE1) as a renal protective medication for patients exposed to contrast agents, as well as to demonstrate the safety, efficacy, and low side-effect profile of PGE1. A prospective, randomized, double-blind study was designed to compare combination of intravenous sodium bicarbonate, normal saline, and oral PGE1 200 μg versus the combination and placebo for renal protection from contrast agents. All patients receiving nonionic contrast during their interventional procedure were eligible for enrollment. Creatinine levels were recorded before and after the administration of contrast and renal protective medications. Contrast-induced nephrotoxicity (CIN) was defined as an increase of 0.5 mg/dL or greater in creatinine level, or an increase of 25% or more above baseline. Age, gender, total amount of contrast used, and incidence of renal failure requiring dialysis were recorded. We conducted the study on 41 patients. Of these, 20 patients received PGE1 and 21 received the placebo. The study group comprised 29 males and 12 females. Diabetes mellitus occurred in 41.5% of the cases (including 40% of PGE1 and 43% of placebo patients). Average contrast use was 77.2 mL (range, 15 to 200 mL). Mean age of the groups was 67.2 years. Average baseline creatinine level was 1.17. The differences between the groups were not statistically significant. CIN by definition occurred in one patient, who received the placebo. Incidence of new onset renal failure requiring dialysis was zero. Postcontrast change in creatinine level for the study was 0.11. There was a change in the creatinine level of 0.161 in the PGE1 group and 0.061 in the placebo group; an improvement of 0.10. PGE1 was not effective in significantly altering postcreatinine levels (p = 0.176). None of the patients enrolled in the study suffered any side effects from taking the PGE1 tablet. Although preliminary, this study shows that the addition of PGE1 for the prevention of CIN is well-tolerated by patients and is a safe modality. Additional studies are required to evaluate efficacy.

Iodinated contrast media cause endothelial damage leading to vasoconstriction of human and rat vasa recta

Contrast-induced acute kidney injury is an important clinical event with a worldwide increasing number of cases. Medullary hypoperfusion and hypoxia due to constriction of vasa recta are main factors in the pathophysiology of acute kidney injury. However, the mechanism of contrast media (CM)-induced vessel constriction is not known. We tested the hypothesis that vasa recta constriction is a consequence of endothelial dysfunction due to the cytotoxicity of CM. Human and rat descending vasa recta (DVR) were isolated and perfused with CM, and the luminal diameter was analyzed. For morphological analysis of the endothelium, renal arteries were CM perfused and then processed for electron microscopy. Transcellular electrical resistance was used to estimate CM-induced changes in the permeability of human umbilical vein endothelial cell (HUVEC) layers. Perfusion with CM constricted human and rat DRV (to 54.3 and 50.9% of initial diameter, respectively). This was blunted by adrenomedullin (77.7 and 77.1%, respectively). The ANG II response was enhanced by CM in rat DVR (reduction to 15.6 and 35.0% of initial diameter, respectively). Adrenomedullin blunted this effect (67.5%). CM led to endothelial damage of renal arteries characterized by a ragged surface, with sharply protruding intimal folds, spindle-like shape, and bulging in the lumen. These phenomena were reduced by adrenomedullin. The permeability of HUVEC cell layers was increased by CM, and this went along with increased myosin light chain phosporylation. Again, adremonedullin reduced the CM effect. Our study suggests that the constrictor effect of CM on the renal medullary microvasculature is a consequence of endothelial cell damage and the resulting endothelial dysfunction.

How to reduce nephropathy following contrast-enhanced CT: a lesson in policy implementation

In excess of 50 contrast-enhanced computed tomography (CT) examinations are typically undertaken in our tertiary hospital NHS Trust each weekday, approximately 13,000 each year. In the Department of Radiology alone, we inject more than 1300 l of iodinated contrast medium per annum. There is a real need to devise a policy to anticipate contrast medium-induced nephropathy (CIN) and minimize its effects, without disrupting the high-intensity CT service. Having written a comprehensive yet pragmatic policy to reduce the incidence of this iatrogenic condition, it seemed sensible to share it with the wider radiology community and share the experience and lessons learnt in engaging all the stakeholders, ushering in the change with as little fuss as possible. The ramifications on primary and secondary care had to be anticipated, resource implications managed, and staff trained. This review is therefore presented in four sections: framing the problem, assessing its size and nature; a succeeding section on the available guidelines and their uptake; the policy itself to reduce CIN in CT is presented in the third section; and crucially, a description of the policy introduction process in the last section.

Pathophysiology of renal tissue damage by iodinated contrast media

1. The present review focuses on the cytotoxic effects of iodinated contrast media (CM) that are shared by all types of CM. 2. Although the clinical nephrotoxicity of CM has been progressively improved, all currently available CM still possess a level of cytotoxicity, which is probably caused by iodine. 3. The toxicity caused by specific CM properties, such as osmolarity, viscosity and ionic strength, can be differentiated from the cytotoxicity common to all CM in studies using cell culture, isolated blood vessels and isolated tubules. 4. The cytotoxicity induced by CM leads to apoptosis and cell death of endothelial and tubular cells and may be initiated by cell membrane damage, together with oxidative stress. 5. Cell damage may be aggravated by factors such as tissue hypoperfusion and hypoxia, properties of individual CM, such as ionic strength, high osmolarity and/or viscosity, and clinically unfavourable conditions. 6. Clinically detectable renal failure may result from the summation of all these factors.

Management of transplant renal artery stenosis

Transplant renal artery stenosis is the most frequent vascular complication of transplantation. Early detection and correction reduce patients' morbidity and allograft dysfunction. Although noninvasive imaging can detect an underlying stenosis, angiography with subsequent angioplasty or stenting, or both, provides definitive diagnosis and treatment. With the introduction of alternative contrast agents and newer catheter and stent technology, these procedures can be performed safely with little risk of contrast-induced nephropathy or allograft loss.

Differentiation of Bosniak categories IIF and III cystic masses: what radiologists should know

Based on a review of the literature, we describe old and new features that both old and new radiologists should be aware of (a) to determine which imaging features affect the differentiation of categories IIF and III masses, (b) to show imaging features of benign cystic renal masses preoperatively diagnosed as category III, and (c) to introduce imaging techniques that help to differentiate categories IIF and III masses without requiring the use of CT or magnetic resonance contrast material.

Transarterial chemoembolization in patients with hepatocellular carcinoma and renal insufficiency

BACKGROUND

Renal dysfunction is often present in patients with cirrhosis and hepatocellular carcinoma (HCC). Acute renal failure (ARF) may occur after transarterial chemoembolization (TACE) owing to radiocontrast agent. This study investigated the incidence and risk factors of ARF and prognostic predictors in HCC patients with preexisting renal insufficiency undergoing TACE.

METHODS

A total of 566 HCC patients undergoing TACE were enrolled. Renal insufficiency was defined as an estimated glomerular filtration rate less than 60 mL/min/1.73 m.

RESULTS

In a mean follow-up duration of 18+/-16 months, 231 (40.8%) patients undergoing TACE died. Renal insufficiency that was present in 134 (23.7%) patients at baseline, independently predicted a poor prognosis in the Cox proportional hazards model [risk ratio (RR): 1.47, P=0.012]. Of them, 13 (10%) and 6 (5%) patients had transient and prolonged ARF after TACE, respectively. Post-TACE gastrointestinal bleeding [odds ratio (OR): 16.54, P=0.001] and higher Cancer of the Liver Italian Program (CLIP) scores (> or =2; OR: 4.22, P=0.02) were independent risk factors for ARF in the multivariate logistic regression analysis. In the Cox model, prolonged ARF (RR: 3.28, P<0.001) and higher CLIP scores (> or =2; RR: 2.13, P<0.001) were independent poor prognostic predictors for HCC patients with renal insufficiency receiving TACE.

CONCLUSIONS

Gastrointestinal bleeding and higher CLIP scores are associated with the development of ARF in patients with HCC and renal insufficiency undergoing TACE. Higher CLIP scores and renal insufficiency, either preexisting before TACE or as a complication of TACE, are poor prognostic predictors in HCC patients receiving TACE.

Incidence of contrast-induced nephropathy after contrast-enhanced computed tomography in the outpatient setting

BACKGROUND AND OBJECTIVES

No prospective study has reported the incidence of contrast-induced nephropathy (CIN) or the associated morbidity and mortality after contrast-enhanced computed tomography (CECT) in the outpatient setting.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We enrolled and followed a prospective, consecutive cohort (June 2007 through January 2009) of patients who received intravenous contrast for CECT in the emergency department of a large, academic, tertiary care center. Outcomes measured were as follows (1) CIN: An increase in serum creatinine > or =0.5 mg/dl or > or =25% 2 to 7 d after contrast administration; (2) severe renal failure: An increase in serum creatinine to > or =3.0 mg/dl or the need for dialysis at 45 d; and (3) renal failure as a contributing cause of death (consensus of three independent physicians) at 45 d.

RESULTS

The incidence of CIN was 11% (70 of 633) among the 633 patients enrolled. Fifteen (2%) patients died within 45 d, including six deaths after study-defined CIN. Seven (1%) patients developed severe renal failure, six of whom had study-defined CIN. Of the six patients with CIN and severe renal failure, four died, and adjudicators determined that renal failure significantly contributed to all four deaths. Thus, CIN was associated with an increased risk for severe renal failure and death from renal failure.

CONCLUSIONS

CIN occurs in >10% of patients who undergo CECT in the outpatient setting and is associated with a significant risk for severe renal failure and death.

Effect of automatic tube current modulation on radiation dose and image quality for low tube voltage multidetector row CT angiography: phantom study

RATIONALE AND OBJECTIVES

To evaluate the effect of automatic tube current modulation on radiation dose and image quality for low tube voltage computed tomography (CT) angiography.

MATERIALS AND METHODS

An anthropomorphic phantom was scanned with a 64-section CT scanner using following tube voltages: 140 kVp (Protocol A), 120 kVp (Protocol B), 100 kVp (Protocol C), and 80 kVp (Protocol D). To achieve similar noise, combined z-axis and xy-axes automatic tube current modulation was applied. Effective dose (ED) for the four tube voltages was assessed. Three plastic vials filled with different concentrations of iodinated solution were placed on the phantom's abdomen to obtain attenuation measurements. The signal-to-noise ratio (SNR) was calculated and a figure of merit (FOM) for each iodinated solution was computed as SNR(2)/ED.

RESULTS

The ED was kept similar for the four different tube voltages: (A) 5.4 mSv +/- 0.3, (B) 4.1 mSv +/- 0.6, (C) 3.9 mSv +/- 0.5, and (D) 4.2 mSv +/- 0.3 (P > .05). As the tube voltage decreased from 140 to 80 kVp, image noise was maintained (range, 13.8-14.9 HU) (P > .05). SNR increased as the tube voltage decreased, with an overall gain of 119% for the 80-kVp compared to the 140-kVp protocol (P < .05). The FOM results indicated that with a reduction of the tube voltage from 140 to 120, 100, and 80 kVp, at constant SNR, ED was reduced by a factor of 2.1, 3.3, and 5.1, respectively, (P < .001).

CONCLUSIONS

As tube voltage decreases, automatic tube current modulation for CT angiography yields either a significant increase in image quality at constant radiation dose or a significant decrease in radiation dose at a constant image quality.