Prevention of contrast media nephrotoxicity--the story so far

Detecting the pulmonary trunk in CT scout views using deep learning

For CT pulmonary angiograms, a scout view obtained in anterior–posterior projection is usually used for planning. For bolus tracking the radiographer manually locates a position in the CT scout view where the pulmonary trunk will be visible in an axial CT pre-scan. We automate the task of localizing the pulmonary trunk in CT scout views by deep learning methods. In 620 eligible CT scout views of 563 patients between March 2003 and February 2020 the region of the pulmonary trunk as well as an optimal slice (“reference standard”) for bolus tracking, in which the pulmonary trunk was clearly visible, was annotated and used to train a U-Net predicting the region of the pulmonary trunk in the CT scout view. The networks’ performance was subsequently evaluated on 239 CT scout views from 213 patients and was compared with the annotations of three radiographers. The network was able to localize the region of the pulmonary trunk with high accuracy, yielding an accuracy of 97.5% of localizing a slice in the region of the pulmonary trunk on the validation cohort. On average, the selected position had a distance of 5.3 mm from the reference standard. Compared to radiographers, using a non-inferiority test (one-sided, paired Wilcoxon rank-sum test) the network performed as well as each radiographer (P < 0.001 in all cases). Automated localization of the region of the pulmonary trunk in CT scout views is possible with high accuracy and is non-inferior to three radiographers.

Predictors and Outcomes of Postcontrast Acute Kidney Injury after Endovascular Renal Artery Intervention

PURPOSE

To determine incidence, predictors, and clinical outcomes of postcontrast acute kidney injury (PC-AKI) following renal artery stent placement for atherosclerotic renal artery stenosis.

MATERIALS AND METHODS

This retrospective study reviewed 1,052 patients who underwent renal artery stent placement for atherosclerotic renal artery stenosis; 437 patients with follow-up data were included. Mean age was 73.6 years ± 8.3. PC-AKI was defined as absolute serum creatinine increase ≥ 0.3 mg/dL or percentage increase in serum creatinine ≥ 50% within 48 hours of intervention. Logistic regression analysis was performed to identify risk factors for PC-AKI. The cumulative proportion of patients who died or went on to hemodialysis was determined using Kaplan-Meier survival analysis.

RESULTS

Mean follow-up was 71.1 months ± 68.4. PC-AKI developed in 26 patients (5.9%). Patients with PC-AKI had significantly higher levels of baseline proteinuria compared with patients without PC-AKI (odds ratio = 1.38; 95% confidence interval, 1.11-1.72; P = .004). Hydration before intervention, chronic kidney disease stage, baseline glomerular filtration rate, statin medications, contrast volume, and iodine load were not associated with higher rates of PC-AKI. Dialysis-free survival and mortality rates were not significantly different between patients with and without PC-AKI (P = .50 and P = .17, respectively).

CONCLUSIONS

Elevated baseline proteinuria was the only predictor for PC-AKI in patients undergoing renal artery stent placement. Patients who developed PC-AKI were not at greater risk for hemodialysis or death.

Contrast-induced acute kidney injury: the importance of diagnostic criteria for establishing prevalence and prognosis in the intensive care unit

OBJECTIVE

To establish whether there is superiority between contrast-induced acute kidney injury and contrast-induced nephropathy criteria as predictors of unfavorable clinical outcomes.

METHODS

Retrospective study carried out in a tertiary hospital with 157 patients undergoing radiocontrast infusion for propaedeutic purposes.

RESULTS

One hundred forty patients fulfilled the inclusion criteria: patients who met the criteria for contrast-induced acute kidney injury (59) also met the criteria for contrast-induced nephropathy (76), 44.3% met the criteria for KDIGO staging, 6.4% of the patients required renal replacement therapy, and 10.7% died.

CONCLUSION

The diagnosis of contrast-induced nephropathy was the most sensitive criterion for renal replacement therapy and death, whereas KDIGO showed the highest specificity; there was no correlation between contrast volume and progression to contrast-induced acute kidney injury, contrast-induced nephropathy, support dialysis or death in the assessed population.

Delayed kidney injury following coronary angiography

It is occasionally observed that patients without contrast-induced nephropathy (CIN) develop kidney injury within 1-6 months after coronary angiography (CAG), termed delayed CIN or delayed kidney injury (DKI) following CAG. The present study aimed to investigate the associated risk factors of delayed CIN and its possible pathogenesis. Subjects with CAG or coronary stenting from January 2008 to December 2009 were studied. A retrospective survey on DKI after CAG was conducted and the risk factors were analyzed. There were 436 cases receiving CAG with complete medical records enrolled in the present cohort, in which the DKI incidence was 7.1% (31/436). Patients with DKI after CAG exhibited lower hemoglobin (121.2±17.3 vs. 133.8±18.6 g/l), estimated glomerular filtration rate (eGFR; 66.4±30.2 vs. 71.9±28.6 ml/min), higher serum creatinine (110.9±43.2 vs. 91.7±37.6 µmol/l), higher rate of heart failure (22.6 vs. 5.4%) and 300 mg aspirin therapy (29 vs. 5.7%) compared with non-DKI patients (all P<0.05). However, no differences were observed in morbidities of diabetes, hypertension, hyperlipidemia and proteinuria, or in the treatments with angiotensin converting enzyme (ACE) inhibitors/angiotensin II receptor-1 blockers (ARBs), diuretics, statins and other anti-platelets between the two groups (P>0.05). Logistic regression revealed that anemia, heart failure and 300 mg aspirin intake were risk factors of DKI (P<0.05), while the contrast level, isotonic contrast, diabetes, ACE inhibitors/ARBs, eGFR and other factors were not associated with DKI (P>0.05). Heart dysfunction and 300 mg aspirin therapy may contribute to DKI after CAG, and iodinated contrast media administration is not a risk factor.

Embolization of hypervascular bone metastases reduces intraoperative blood loss: a case-control study

BACKGROUND

Small case series suggest that preoperative transcatheter arterial embolization minimizes bleeding and facilitates surgery for hypervascular metastatic bone tumors. However, control groups would make our confidence in clinical recommendations stronger, but small patient numbers make prospective trials difficult to conduct on this topic.

QUESTIONS/PURPOSES

In this case-control study, we asked whether (1) patients who undergo embolization have less estimated blood loss and/or shorter operative time than patients who do not have embolization; (2) larger tumor size, greater initial tumor vascularity, and longer interval from embolization to surgery are associated with greater estimated blood loss and packed red blood cell transfusion volume; and (3) embolization does not affect renal function in patients with normal preoperative renal function.

METHODS

We retrospectively reviewed records of patients with hypervascular bone metastases treated at our institution between 1998 and 2008. Twenty-seven patients with renal cell carcinoma and 12 with thyroid carcinoma who underwent embolization before 41 surgical procedures were matched to 41 patients who did not have embolization with respect to age, diagnosis, tumor size and potential vascularity, and procedure type; matching was performed without knowledge of outcomes. In univariate and multivariate analyses, age, tumor size, use of embolization, surgery type and risk, embolization-to-surgery interval, and degree of devascularization were evaluated for correlations with estimated blood loss, packed red blood cell transfusion volume, operative time, and postembolization renal function.

RESULTS

Overall, patients who had embolization had less mean estimated blood loss (0.90 versus 1.77 L; p = 0.002), packed red blood cell transfusion volume (2.15 versus 3.56 U; p = 0.020), and operative time (3.13 versus 3.91 hours; p < 0.001). Larger tumor size correlated with greater estimated blood loss (r = 0.451; p = 0.003), packed red blood cell transfusion volume (r = 0.50; p = 0.002), and operative time (r = 0.595; p < 0.001). Neither the interval for embolization to surgery nor the degree of devascularization correlated with estimated blood loss or transfusion volume. In open rodding with intralesional curettage, transcatheter arterial embolization was associated with reduced estimated blood loss, transfusion volume, and operative time. Packed red blood cell transfusion volume was not reduced by embolization in intramedullary nailing procedures with the patient numbers available. Among patients with normal preoperative renal function who had embolization, creatinine levels remained normal. Mild transient, reversible renal function change occurred in one patient with preoperatively abnormal renal function.

CONCLUSIONS

This study suggests that preoperative embolization probably reduces estimated blood loss, particularly for large tumors and during open femoral procedures.

Can selective inhibitors of cyclic guanosine monophosphate (cGMP)-specific phosphadiesterase type 5 (PDE 5) offer protection against contrast induced nephropathy?

Parenchymal hypoxia within the renal outer medulla plays an important role in the pathogenesis of contrast induced nephropathy (CIN). Nitric oxide (NO) is crucial for medullary oxygenation by enhancing regional blood flow. Augmenting the effect of NO in the renal medulla by the use of selective inhibitors of cyclic guanosine monophosphate (cGMP)-specific phosphadiesterase type 5 (PDE 5) such as sildenafil (Viagra™), vardenafil (Levitra™) or tadalafil (Cialis™) could reduce the severity of the hypoxic insult induced by the contrast medium and reduce the risk of CIN. Prophylactic administration of one of these drugs particularly the long acting one tadalafil before and after the administration of CM could offer a simple and rational approach to reduce the risk of this complication. This hypothesis deserves serious investigation to determine its clinical efficacy.

A simple preprocedural score for risk of contrast-induced acute kidney injury after percutaneous coronary intervention

OBJECTIVE

To develop a simple scoring system based on preprocedural clinical features that is capable of predicting contrast-induced acute kidney injury (CI-AKI) before percutaneous coronary intervention (PCI).

BACKGROUND

CI-AKI is associated with increased in-hospital morbidity and mortality, prolonged hospitalization, and long-term renal impairment. Although several scoring methods have been developed to determine risk of CI-AKI, no simple scoring method based on PCI preprocedural clinical features yet exists for Chinese patients.

METHODS

A total of 2,500 Chinese patients were randomly and retrospectively assigned in a 3:2 manner to create a training and validation dataset, respectively. CI-AKI was defined as an increase of ≥25% or ≥0.5 mg/dL serum creatinine within 5 days after PCI. Preprocedural clinical variables showing independent correlation to CI-AKI were used to derive the risk score from the training dataset and then subsequently tested in the validation dataset. The odds ratios from multivariate logistic regression were used to assign a weighted integer to age ≥70 years = 4, history of myocardial infarction = 5, diabetes mellitus = 4, hypotension = 6, left ventricular ejection fraction ≤45% = 4, anemia = 3, creatinine clearance rate <60 mL/min = 7, decreased high-density lipoprotein <1 mmol/L= 3, and urgent PCI = 3. Summation of the integers represented the total risk score.

RESULTS

The overall incidence of CI-AKI in the training dataset was 16.4% [246/1500; 5.4% for low (≤7) and 61.3% for very high (≥17) risk scores]. The rates of CI-AKI, 1-year dialysis, and 1-year mortality increased significantly with each group (Cochran-Armitage test of trend, P < 0.001). The risk score facilitated appropriate classification of patients with low and high risk for CI-AKI after PCI in the validation dataset (c-statistic = 0.82).

CONCLUSION

Risk classification based on the most significantly correlated parameters is useful for predicting CI-AKI before contrast exposure. The simple preprocedural score showed excellent predictive ability for identifying patients at high risk of nephropathy and those with deteriorative prognosis after PCI.

Interventions for protecting renal function in the perioperative period

BACKGROUND

Various methods have been used to try to protect kidney function in patients undergoing surgery. These most often include pharmacological interventions such as dopamine and its analogues, diuretics, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, N-acetyl cysteine (NAC), atrial natriuretic peptide (ANP), sodium bicarbonate, antioxidants and erythropoietin (EPO).

OBJECTIVES

This review is aimed at determining the effectiveness of various measures advocated to protect patients' kidneys during the perioperative period.We considered the following questions: (1) Are any specific measures known to protect kidney function during the perioperative period? (2) Of measures used to protect the kidneys during the perioperative period, does any one method appear to be more effective than the others? (3) Of measures used to protect the kidneys during the perioperative period,does any one method appear to be safer than the others?

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 2, 2012), MEDLINE (Ovid SP) (1966 to August 2012) and EMBASE (Ovid SP) (1988 to August 2012). We originally handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery) (1985 to 2004). However, because these journals are properly indexed in MEDLINE, we decided to rely on electronic searches only without handsearching the journals from 2004 onwards.

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery for which a treatment measure was used for the purpose of providing renal protection during the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 72 studies for inclusion in this review. Two review authors extracted data from all selected studies and entered them into RevMan 5.1; then the data were appropriately analysed. We performed subgroup analyses for type of intervention, type of surgical procedure and pre-existing renal dysfunction. We undertook sensitivity analyses for studies with high and moderately good methodological quality.

MAIN RESULTS

The updated review included data from 72 studies, comprising a total of 4378 participants. Of these, 2291 received some form of treatment and 2087 acted as controls. The interventions consisted most often of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, NAC, ANP, sodium bicarbonate, antioxidants and EPO or selected hydration fluids. Some clinical heterogeneity and varying risk of bias were noted amongst the studies, although we were able to meaningfully interpret the data. Results showed significant heterogeneity and indicated that most interventions provided no benefit.Data on perioperative mortality were reported in 41 studies and data on acute renal injury in 44 studies (all interventions combined). Because of considerable clinical heterogeneity (different clinical scenarios, as well as considerable methodological variability amongst the studies), we did not perform a meta-analysis on the combined data.Subgroup analysis of major interventions and surgical procedures showed no significant influence of interventions on reported mortality and acute renal injury. For the subgroup of participants who had pre-existing renal damage, the risk of mortality from 10 trials (959 participants) was estimated as odds ratio (OR) 0.76, 95% confidence interval (CI) 0.38 to 1.52; the risk of acute renal injury (as reported in the trials) was estimated from 11 trials (979 participants) as OR 0.43, 95% CI 0.23 to 0.80. Subgroup analysis of studies that were rated as having low risk of bias revealed that 19 studies reported mortality numbers (1604 participants); OR was 1.01, 95% CI 0.54 to 1.90. Fifteen studies reported data on acute renal injury (criteria chosen by the individual studies; 1600 participants); OR was 1.03, 95% CI 0.54 to 1.97.

AUTHORS' CONCLUSIONS

No reliable evidence from the available literature suggests that interventions during surgery can protect the kidneys from damage. However, the criteria used to diagnose acute renal damage varied in many of the older studies selected for inclusion in this review, many of which suffered from poor methodological quality such as insufficient participant numbers and poor definitions of end points such as acute renal failure and acute renal injury. Recent methods of detecting renal damage such as the use of specific biomarkers and better defined criteria for identifying renal damage (RIFLE (risk, injury, failure, loss of kidney function and end-stage renal failure) or AKI (acute kidney injury)) may have to be explored further to determine any possible benefit derived from interventions used to protect the kidneys during the perioperative period.

Clinical survey on contrast-induced nephropathy after coronary angiography

OBJECTIVE

To investigate the incidence and risk factors of contrast-induced nephropathy (CIN) in patients receiving coronary angiography (CAG) in a Chinese medical center.

METHODS

The medical records of the patients receiving CAG at Shanghai Sixth People's Hospital Affiliated to Shanghai Jiaotong University from January 2008 to July 2009 were collected to analyze the incidence of CIN under different conditions and the clinical difference between CIN group and non-CIN group.

RESULTS

There were 487 cases enrolled in this study and the total incidence of CIN was 10.5%. Through Mehran risk score stratification, incidence of CIN increased with risk scores and in an extremely high-risk group it was as high as 18.0%. Multi-factor regression analysis showed that preoperative hypotension, heart failure, anemia and low estimated glomerular filtration rate (≤30 mL/min) were risk factors of CIN after CAG.

CONCLUSION

CIN post CAG is associated with preoperative hypotension, heart failure, anemia and renal function. Close attention should be paid to CIN in patients receiving CAG.

Contrast-induced acute kidney injury following PCI

BACKGROUND

Coronary revascularization using percutaneous coronary intervention (PCI) is one of the major treatments for patients with stable coronary artery disease, with approximately 1.5 million patients undergoing PCI in the United States and Europe every year. An important neglected complication of PCI is contrast-induced acute kidney injury (CI-AKI).

DESIGN

In this article, we review the definition, pathogenesis and management of CI-AKI and highlight potential therapeutic options for preventing CI-AKI in post-PCI patients.

RESULTS

CI-AKI is an important but underdiagnosed complication of PCI that is associated with increased in-hospital morbidity and mortality. Patients with pre-existing renal impairment and diabetes are particularly susceptible to this complication post-PCI. Optimization of the patients' circulating volume remains the mainstay for preventing CI-AKI, although the best strategy for achieving this is still controversial.

CONCLUSION

Following PCI, CI-AKI is an overlooked complication which is associated with significant morbidity and mortality. In this article, we review the pathophysiology of CI-AKI in patients undergoing PCI and discuss the potential therapeutic options for preventing it.

Efficacy of N-acetylcysteine and aminophylline in preventing contrast-induced nephropathy

BACKGROUND

Contrast-induced nephropathy (CIN) is one of the important complications of coronary angiography (CAG) and percutaneous coronary intervention (PCI), especially in patients with chronic kidney disease (CKD). Prophylactic administration of N-acetylcysteine (NAC) and aminophylline has been reported to be effective in some trials, but the results still remain controversial. We investigated the efficacy of NAC or aminophylline in preventing CIN.

METHODS AND RESULTS

Forty-five consecutive patients undergoing CAG and/or PCI were randomly assigned to receive hydration and NAC (704 mg orally twice daily; NAC group, n=15), hydration and aminophylline (250 mg intraveneously 30 min before CAG and/or PCI; aminophylline group, n=15), or hydration alone (control group, n=15). We compared serum creatinine (SCr), creatinine clearance (Ccr), blood beta-2 microglobulin, and urinary beta-2 microglobulin levels at baseline and 48h after CAG and/or PCI. In the NAC group, SCr decreased from 1.00 + or - 0.36 to 0.67 + or - 0.16 mg/dl (p<0.01), and Ccr significantly increased from 62.4 + or - 15.6 to 80.4 + or - 8.39 ml/min (p<0.01). In the aminophylline group, SCr and Ccr were unchanged. In the control group, SCr significantly increased from 0.94 + or - 0.21 to 1.28 + or - 0.21 mg/dl (p<0.01), and Ccr significantly decreased from 63.7 + or - 16.1 to 46.1 + or - 10.6 ml/min (p<0.01) after CAG and/or PCI. In the NAC group, mean blood beta-2 microglobulin significantly decreased from 2.38 + or - 0.58 to 1.71 + or - 0.38 mg/dl (p<0.01), and in the aminophylline group, mean urinary beta-2 microglobulin concentration significantly decreased from 337 + or - 31.0 to 239 + or - 34 microg/ml (p<0.01).

CONCLUSIONS

These results suggest that both prophylactic NAC and aminophylline administration are effective in preventing CIN, but not with hydration alone. It appears that the two compounds work in different ways against CIN.

Prevention of contrast-induced nephropathy: an overview

Many unknowns remain concerning how best to reduce a patient's risk of contrast-induced nephropathy (CIN). Many interventions have been proposed, but few have gone unchallenged, and new questions have arisen from analysis of serum creatinine variations in patients who have not been exposed to radiographic iodinated contrast media (RICM). Use of alternate imaging tests that do not use RICM is the most direct way to avoid CIN. Hydration remains the bulwark of intervention when RICM must be administered. The administration of N-acetylcysteine is a popular pharmacologic prophylaxis against CIN but its efficacy is unclear. Hemodialysis has not been effective, but hemofiltration has shown good results in limited series.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine and its analogues, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes that included renal failure and mortality as well as changes in renal function tests, such as urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to June, 2007), and EMBASE (1988 to June, 2007); and handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 53 studies for inclusion in this review. As well as data analysis from all the studies, we performed subgroup analysis for type of intervention, type of surgical procedure, and pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high and moderately good methodological quality.

MAIN RESULTS

The review included data from 53 studies, comprising a total of 2327 participants. Of these, 1293 received some form of treatment and 1034 acted as controls. The interventions mostly consisted of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, or selected hydration fluids. The results indicated that certain interventions showed minimal benefits. All the results suffered from significant heterogeneity. Hence we cannot draw conclusions about the effectiveness of these interventions in protecting patients' kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from the available literature to suggest that interventions during surgery can protect the kidneys from damage. There is a need for more studies with high methodological quality. One particular area for further study may be patients with pre-existing renal dysfunction undergoing surgery.

Contrast medium-induced nephropathy. Aspects on incidence, consequences, risk factors and prevention

Contrast media-induced nephropathy (CIN) is a well-known complication of radiological examinations employing iodine contrast media (I-CM). The rapid development and frequent use of coronary interventions and multi-channel detector computed tomography with concomitant administration of relatively large doses of I-CM has contributed to an increasing number of CIN cases during the last few years. Reduced renal function, especially when caused by diabetic nephropathy or renal arteriosclerosis, in combination with dehydration, congestive heart failure, hypotension, and administration of nephrotoxic drugs are risk factors for the development of CIN. When CM-based examinations cannot be replaced by other techniques in patients at risk of CIN, focus should be directed towards analysis of number and type of risk factors, adequate estimation of GFR, institution of proper preventive measures including hydration and post-procedural observation combined with surveillance of serum creatinine for 1-3 days. For the radiologist, there are several steps to consider in order to minimise the risk for CIN: use of "low-" or "iso-osmolar" I-CM and dosing the I-CM in relation to GFR and body weight being the most important as well as utilizing radiographic techniques to keep the I-CM dose in gram iodine as low as possible below the numerical value of estimated GFR. There is as yet no pharmacological prevention that has been proven to be effective.

Coronary venous capture of contrast during angiography

Contrast-induced nephropathy (CIN) after angiographic procedures results in significant morbidity, mortality, and costs. Given the limitations of current prophylactic measures, we have tested the hypothesis that the majority of the contrast injected into a coronary artery can be captured from the coronary sinus before it enters the systemic circulation. The current study involves coronary venous capture after coronary angiography in dogs with determination of contrast capture using quantitative fluoroscopy. Venous contrast capture (VCC) was achieved with a balloon tipped through lumen catheter introduced into the coronary sinus via the superior vena cava. After selective injection of iohexol contrast into the left main coronary artery, the coronary sinus was balloon occluded in order to capture all contrast. The venous blood was subsequently withdrawn from the coronary sinus catheter, and then the balloon was deflated. By quantitative fluoroscopy we could demonstrate that an average 70 +/- 6% of the injected contrast could be captured without complications. Coronary sinus VCC is a novel approach to remove the majority of contrast selectively injected into coronary arteries. As an adjunct procedure in coronary angiography, VCC has the potential to significantly reduce the risk of CIN in patients at risk.

European Society of Urogenital Radiology (ESUR) guidelines on the safe use of iodinated contrast media

Since 1996 the Contrast Media Safety Committee of the European Society of Urogenital Radiology (ESUR) has released 19 guidelines regarding safety in relation to the use of radiographic, ultrasonographic as well as magnetic resonance contrast media. The committee has covered both renal and non-renal adverse events as well as other aspects of contrast media. The present paper is an overview of the work accomplished over the last 10 years regarding radiographic iodinated contrast media.

Facts and fallacies concerning the prevention of contrast medium-induced nephropathy

OBJECTIVE

The aim of this article is to extract from recent medical literature and nephrologic practice the facts and fallacies concerning the possible prophylaxis of contrast medium-induced nephropathy.

DATA SOURCES, STUDY SELECTION, AND DATA EXTRACTION

A MEDLINE/PubMed search (1985 to January 2006) was conducted, including all relevant articles investigating the pathogenesis and prevention of contrast medium-induced nephropathy from a nephrologic critical point of view.

DATA SYNTHESIS

Considerable efforts have been made to develop pharmacologic therapy for the prevention of contrast medium-induced nephropathy, especially in patients at risk, such as elderly subjects and those with preexisting renal impairment, hypovolemia, or dehydration. There is general consensus that hydration protocols implemented before and after imaging with contrast medium may be effective in preventing contrast medium-induced nephropathy. However, definitive and convincing data related to amounts to be infused, infusion timing, and type of solutions (half-isotonic, isotonic saline solution, or bicarbonate) are lacking. Forced diuresis with furosemide or mannitol and use of dopamine, together with concomitant hydration, have been proved to be ineffective or even more risky in the event of inadequate maintenance of euvolemia. Various direct or indirect vasodilators have been investigated (atrial natriuretic peptide, calcium channel blockers, angiotensin-converting enzyme inhibitors, and endothelin receptor antagonists), yet results have been inconsistent and inconclusive. Recent large meta-analyses concerning the protective role of antioxidant action of N-acetylcysteine have led to the conclusion that the statistical significance of the results is borderline. Preventive hemodialysis has not proved to be useful; on the contrary, it might worsen the clinical conditions by inducing hypotension. Hemofiltration, despite some positive studies, is too complex and cannot be used extensively.

CONCLUSIONS

: It is believed that prevention is actually achieved by correcting hypovolemia, dehydration, or both. Normalization of body fluids is probably the true objective to be achieved by preventive measures in all patients, not only in those at risk. Because limited data have been collected in intensive care units, at present, no firm or specific recommendations can yet be provided for the critically ill.

Use of intra-arterial multi-detector row CT angiography for the evaluation of an ischaemic limb in a patient with renal impairment

The vastly improved scanning speed and z-axis resolution afforded by multi-detector technology has allowed CT to refine its traditional roles and to explore many new applications in imaging. We present a case report of a patient with renal failure and an ischaemic leg, which illustrates a useful new CT vascular imaging application. By carrying out 16-channel multi-detector row CT angiography through a sheath introduced into the common femoral artery, we obtained a high-quality angiographic image of the affected leg, using only 30 mL of iodinated contrast material. The examination definitively showed the number, distribution and patency of the tibial run-off arteries, with significant influence on the patient's subsequent clinical management. This simple and relatively minimally invasive technique is useful in peripheral vascular imaging, when conventional CT angiography using a large volume of i.v. contrast and MR angiography are unsuitable or unavailable.

Prophylactic hemodialysis does not prevent contrast-induced nephropathy after cardiac catheterization in patients with chronic renal insufficiency

BACKGROUND

In Japan, prophylactic hemodialysis has been considered useful for preventing contrast-induced nephropathy (CIN).

METHOD AND RESULTS

To assess whether hemodialysis prevented CIN, 391 patients (age: 69 +/- 8 years, 63 females) with chronic renal insufficiency (CRI, serum creatinine level (Scr) > or = 1.3 mg/dl) who underwent cardiac catheterization, were retrospectively analyzed. Patients were divided into 3 categories based on Scr: L (1.3 > or = Scr < 2.0 mg/dl, n = 332); M (2.0 > or = Scr < 3.0 mg/dl, n = 49); and H (Scr > or = 3.0 mg/dl, n = 10). To prevent CIN, 35 category M patients and all category L patients received hydration alone, whereas 14 category M patients and all category H patients received hemodialysis. CIN developed in 48 patients. The incidence of CIN in category H was significantly higher than that in category L or M (H, 40% vs L, 11% or M, 16% (p < 0.05)). In category M patients treated with hemodialysis, Scr increased from 2.4 +/- 0.3 to 3.0 +/- 0.5 mg/dl (p < 0.05) within 7 days, and 29% of patients developed CIN. However, in category M patients who did not receive hemodialysis, the Scr did not change (pre, 2.3 +/- 0.2 mg/dl to post, 2.2 +/- 0.4 mg/dl), and the incidence of CIN was 11%.

CONCLUSION

Prophylactic hemodialysis for CRI patients undergoing cardiac catheterization does not prevent CIN.

Endovascular and interventional procedures in obese patients: a review of procedural technique modifications and radiation management

As the prevalence of obesity in the United States continues to increase, the volume of endovascular and fluoroscopically guided procedures is also increasing. With obese patients, it often seems the only consideration is whether the table weight tolerance can accommodate the patient. This is a naive approach to performing procedures in obese patients, as there are multiple considerations involved in providing state-of-the-art endovascular and interventional care to obese patients. A growing collection of literature is beginning to surface regarding the appropriate modifications in the interventional care of these patients. This article reviews the relevant literature on this important subject.

Concomitant unilateral internal iliac artery embolization and endovascular infrarenal aortic aneurysm repair

INTRODUCTION

Endograft limb extension to the external iliac artery with embolization of an internal iliac artery (IIA) may be necessary in patients with abdominal aortic aneurysms (AAAs) extending to the common iliac artery to prevent endoleak during endovascular aortic aneurysm repair (EVAR). Coil embolization of the IIA can be performed at the same operative setting as EVAR or, alternatively, as a staged procedure. Most interventionalists favor the latter approach to avoid excessive contrast material and prolonged operative time. We investigated the clinical outcome of concomitant vs staged unilateral IIA embolization in the setting of EVAR.

METHODS

Vascular surgeons at our institution treated 24 patients with infrarenal EVAR and unilateral coil embolization of the IIA from October 1, 2000 to June 30, 2005. All patients had normal renal function. The details of the operative procedure and perioperative complications were compared in patients undergoing concomitant vs staged procedures. Follow up was 1 to 40 months (average, 11 months).

RESULTS

Among the 24, 16 underwent concomitant unilateral IIA embolization in the setting of EVAR and eight patients underwent the staged procedure. Average duration of operative time (298 vs 284 minutes), amount of intravenous contrast (215 mL vs 164 mL), and preoperative (1.12 vs 1.26 mg/dL), and postoperative (1.15 v. 1.31 mg/dl) creatinine levels were similar in the concomitant vs staged group, respectively (P > .05 for all factors). More sensitive markers of renal insufficiency such as creatinine clearance were not measured. In the concomitant group, 25% (4/16) of patients reported significant symptoms of buttock claudication ipsilateral to the embolized IIA, which resolved after a mean of 8.8 months (range, 1 to 15 months) vs no cases (0/8) in the staged group (P = .02048). One patient in the staged group developed ischemic colitis, which was treated conservatively. Coil embolizations that were performed as staged procedures were all done on an outpatient basis. All 24 patients were admitted the day of the EVAR and were discharged the next day, except one patient in the concomitant group was discharged the second day after the procedure, and one patient in the staged group was discharged 7 days after the procedure.

CONCLUSION

Despite concern of prolonged operative time and the amount of contrast needed to perform concomitant IIA embolization and EVAR, our results showed that in patients with normal renal function, concomitant unilateral IIA embolization in the setting of EVAR was safe and effective and associated with shorter hospitalization compared with staged procedures. The disadvantage of a concomitant procedure is an increased likelihood of transient buttock claudication, but the small number of patients in this series prohibits definite conclusions about this complication. The concomitant procedure may be preferable for infirm patients with normal renal function who would be greatly inconvenienced by two procedures.

ESUR guidelines on contrast media

Since 1996 the Contrast Media Safety Committee of the European Society of Urogenital Radiology has released 15 guidelines regarding safety in relation to the use of radiographic, ultrasonographic, and magnetic resonance contrast media. The guidelines have been well received by the radiologic community in Europe and all over the world and comprise current standards for good practice at many institutions. The present report is an overview of the work accomplished by the European Society of Urogenital Radiology over the past 8 years. The committee has covered renal and nonrenal adverse events and other aspects of contrast media.

[Multislice CT urography Aspects for technical management and clinical application]

The introduction of multislice computed tomography with its well-known advantages has made it possible to visualize the entire urinary tract with thin collimation during a breath-holding phase. CT data acquisition during urographic contrast enhancement for contiguous imaging of the entire upper urinary tract is termed "multislice CT urography" (MSCTU). Multiplanar reconstructions, maximum intensity projections, and average intensity projections can be rendered from the volume datasets to view the urogenital tract. MSCTU will play an important role in the future of modern uroradiology. This article describes the technical aspects involved in the course of the MSCTU examination and identifies additional potential indications for clinical application.

Outcomes of contrast-induced nephropathy: Experience in patients undergoing cardiovascular intervention

Use of iodinated contrast media for diagnostic and interventional procedures is increasing as computed tomography and percutaneous coronary intervention (PCI) technologies provide increasing patient benefit. Although some complications associated with contrast media are mild and transient, contrast-induced nephropathy (CIN) can negatively affect long-term patient morbidity and mortality. The incidence of and outcomes from CIN have been carefully studied in cardiology patients. A number of studies have identified CIN-associated complications in PCI patients, including bleeding, hematoma, stroke, adult respiratory distress syndrome, electrolyte imbalances, and sepsis. In post-PCI patients, rates of myocardial infarction and vessel reocclusion are more common in patients with CIN. Therefore, in-hospital mortality is increased in patients with CIN. In patients requiring dialysis after PCI, several studies have shown the 1-year mortality rate to be >55%. Even moderate renal dysfunction not requiring dialysis is associated with increased mortality in patients with coronary artery disease. Precautionary measures before, during, and after the use of contrast media that reduce the incidence of CIN, such as discontinuation of nephrotoxic medications, adequate hydration, and use of appropriate volumes and types of contrast media, should be considered in all patients with renal insufficiency or with other risk factors for CIN.

Reducing the Risks for Contrast-Induced Nephropathy

Contrast-induced nephropathy (CIN) is one of the most serious adverse events associated with the use of contrast media (CM). Patients who develop this complication can have increased morbidity, higher rates of mortality, lengthy hospital stays, and poor long-term outcomes. Although CIN cannot be eliminated, the chances of developing this condition can be reduced by using appropriate prevention strategies. An important first step to reduce the chance of CIN is to identify risk factors associated with this condition. Patients with a previously elevated serum creatinine level, especially when secondary to diabetic nephropathy, are at great risk for developing CIN. Other patient-related risk factors include concurrent use of nephrotoxic medications, dehydration, congestive heart failure, age greater than 70 years, and probably the presence of diabetes mellitus even if serum creatinine is normal. Adequate hydration is widely accepted as an important prophylactic measure for preventing CIN, but the optimal hydration regimen is still debatable. The risk of CIN increases with greater doses of CM, as well as with the type of CM used. A high-osmolar CM poses a greater risk of CIN than does a low-osmolar CM and, as recent but limited data suggest, the use of an isoosmolar CM is less nephrotoxic than a low-osmolar CM in patients with renal impairment following intra-arterial procedures, although this finding needs to be verified in future clinical studies. Pharmacologic agents such as calcium channel blockers, dopamine, atrial natriuretic peptide, fenoldopam, prostaglandin El, and endothelin receptor antagonist have not been proven effective against CIN development. Controversies still exist on the possible effectiveness of theophylline and N-acetylcysteine. Simple strategies for the prevention of CIN in at-risk patients are reviewed and unproven interventions are discussed.

Nephropathy induced by contrast media: pathogenesis, risk factors and preventive strategies

With the increasing use of contrast media in diagnostic and interventional procedures, nephropathy induced by contrast media has become the third leading cause of hospital-acquired acute renal failure. It is also associated with a significant risk of morbidity and death. The current understanding of the pathogenesis indicates that contrast-medium nephropathy is caused by a combination of renal ischemia and direct toxic effects on renal tubular cells. Patients with pre-existing renal insufficiency, diabetes mellitus and congestive heart failure are at highest risk. Risk factors also include the type and amount of contrast medium administered. Therapeutic prevention strategies are being extensively investigated, but there is still no definitive answer. In this article, we review the current evidence on the causes, pathogenesis and clinical course of contrast-medium nephropathy as well as therapeutic approaches to its prevention evaluated in clinical trials.

Pathophysiology of contrast medium-induced nephropathy

BACKGROUND

Contrast medium-induced nephropathy (CIN) is a well-known cause of acute renal failure, but the development of CIN remains poorly understood. A number of studies have been performed with the one aim, to shed some light onto the pathophysiology of CIN. These have led to manifold interpretations and sometimes contradicting conclusions.

METHODS

This review critically surveys mechanisms believed to mediate CIN by highlighting the complex pathophysiologic entity, including altered rheologic properties, perturbation of renal hemodynamics, regional hypoxia, auto- and paracrine factors [adenosine, endothelin, and reactive oxygen species (ROS)], and direct cytotoxic effects. Moreover, the importance of physicochemical properties of contrast media are made clear.

RESULTS

The more recently developed iso-osmolar contrast media are dimers, not monomers as the widely used nonionic low osmolar contrast media. The dimers have physicochemical features different from other contrast media which may be of clinical importance, not only with respect to osmolality. The viscosity of the commercially available dimers is considerably higher than blood.

CONCLUSION

Many experimental studies provide evidence for a greater perturbation in renal functions by dimeric contrast media in comparison to nonionic monomeric contrast media. Clinical trials have yielded conflicting results.

Contrast Dose-to-Creatinine Clearance Ratio as a Potential Indicator of Risk for Radiocontrast-Induced Nephropathy

OBJECTIVES

Identification of risk factors is important for preventing radiocontrast-induced nephropathy (RCIN). Contrast dose and renal function have been shown in most but not all studies to be risk factors for RCIN. We are investigating the ratio of contrast dose to creatinine clearance (D/CrCL) as a risk indicator. Theory shows that the D/CrCL ratio equals the area under the concentration-time curve (AUC), an accepted measure of systemic exposure. This study investigated the correlation between calculated D/CrCL and experimentally measured AUC for the contrast agent iodixanol.

MATERIALS AND METHODS

Experimental data on AUC from a phase 1 study of iodixanol were plotted against the D/CrCL ratio and the degree of correlation was determined.

RESULTS

Experimentally determined AUC data correlate highly with the D/CrCL ratio.

CONCLUSIONS

The D/CrCL ratio is a rapid and accurate way to estimate AUC for an iodinated x-ray contrast agent without the need for multiple blood samples.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials, which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes such as renal failure and mortality, as well as changes in the renal function tests, including urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004), MEDLINE (1966 to 2004) and EMBASE (1988 to 2004) and hand searched six journals (British Journal of Anaesthesia; Anesthesia and Analgesia; Anesthesiology; Annals of Surgery; Journal of Thoracic and Cardiovascular Surgery and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adult population undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 37 studies for inclusion in this review. As well as analysis of the data from all the studies, we also performed subgroup analysis for type of interventions, types of surgical procedures and those with pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high methodological quality.

MAIN RESULTS

The review included data from 37 studies, comprising a total of 1227 patients. Of these, 658 received some form of treatment and 569 acted as controls. The interventions were mostly employing different pharmaceutical agents such as dopamine, diuretics, calcium channel blockers. ACE inhibitors or selected hydration fluids. The results indicated that certain interventions showed some benefits, but all the results suffered from significant heterogeneity. Hence we can draw no conclusions about the effectiveness of these interventions in protecting the kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from available literature to suggest that interventions during surgery can protect the kidneys from damage. However, there is a need for more studies of high methodological quality. One particular area for further studies may be on patients with pre-existing renal dysfunction undergoing surgery.

Néphropathie induite par les produits de contraste iodés, l’épuration extrarénale est-elle efficace en prevention ?

A FREQUENT AND EXPENSIVE PROBLEM: Ninety percent of contrast media nephrotoxicity (CMN) occur in patients with pre-existing kidney failure. Its aggravation may require early chronic dialysis.

PREVENTIVE MEASURES

CMN prophylaxis is important in these patients. Pre- and post-hydration, with infusion of isotonic saline solution or sodium bicarbonate, and reduction of contrast medium (CM) volume to the strict minimum are essential for preventing CM-induced kidney failure. THE INTEREST OF PROPHYLACTIC HEMODIALYSIS AND HEMOFILTRATION: An interesting approach in preventing CMN is the early elimination of the CM with dialysis techniques. Preventive hemodialysis does not reduce the risk of CMN, but hemofiltration has shown significant efficacy in a population of patients with kidney failure. THE INTEREST OF IMMEDIATE HEMODIALYSIS IN CHRONIC HEMODIALYSIS PATIENTS: Although nephrotoxicity is no longer a problem in patients undergoing chronic hemodialysis, CM, especially in high-dose injections, may be responsible for fluid and electrolyte abnormalities and/or volemic expansion. No data yet justify a conclusion that a hemodialysis session immediately after injection of a CM in chronic dialysis patients might be helpful.

Contrast-induced nephropathy

Contrast-induced nephropathy (CIN) is a leading cause of in-hospital acute renal failure in critically ill patients who undergo radiographic procedures. Critical care patients are at particular risk, often because of baseline renal dysfunction, older age, and the presence of diabetes. In addition, there are superimposed risks, including volume depletion, sepsis, and use of nephrotoxic drugs. The rates of CIN (defined as an increase in serum creatinine by >25% or 0.5 mg/dL) can be predicted by using multivariate tools. Prevention measures include adequate hydration, use of N-acetylcysteine and iso-osmolar contrast, and for patients who are at the highest risk, prophylactic hemofiltration.

Recent advances in the prevention of radiocontrast-induced nephropathy

PURPOSE OF REVIEW

Radiocontrast nephropathy is a serious clinical problem associated with increased morbidity and mortality, particularly in patients with chronic renal failure. The optimal strategy to prevent radiocontrast nephropathy has not been established. This article reviews recent clinical researches concerning new developments in the prevention of radiocontrast nephropathy and analyzes unresolved issues.

RECENT FINDINGS

Among all prophylactic measures that have been proposed, periprocedural hydration with isotonic saline has demonstrated effectiveness in the prevention of radiocontrast nephropathy. Thus, it remains the most frequently applied measure in clinical practice. Recently, additional benefit has been shown to derive from the infusion of isotonic alkalizing (sodium bicarbonate), instead of isotonic (sodium chloride) solutions. The use of nonionic low-osmolar and, more recently, nonionic iso-osmolar contrast agents has been demonstrated to significantly reduce the risk of radiocontrast nephropathy in patients with renal impairment, in comparison with hyperosmolar contrast media. Recently, periprocedural hemofiltration has emerged as a safe and very effective strategy to prevent radiocontrast nephropathy and to reduce its associated poor outcome in patients with severe chronic renal failure. In the past few years, several trials with acetylcysteine have shown conflicting results. Nevertheless, most of them indicated that acetylcysteine, particularly when associated with adequate hydration, might be useful in preventing radiocontrast nephropathy in patients with renal impairment. A possible dose-dependent protective effect has been suggested by more recent trials that included patients undergoing coronary interventional procedures requiring large contrast volume.

SUMMARY

Adequate prophylaxis is needed to reduce the high morbidity and mortality associated with radiocontrast nephropathy in high-risk patients. By reviewing the available evidence from clinical trials, this article provides an overview of current strategies and unresolved issues concerning the prevention of radiocontrast nephropathy.

Bench-to-bedside review: preventive measures for contrast-induced nephropathy in critically ill patients

An increasing number of diagnostic imaging procedures requires the use of intravenous radiographic contrast agents, which has led to a parallel increase in the incidence of contrast-induced nephropathy. Risk factors for development of contrast-induced nephropathy include pre-existing renal dysfunction (especially diabetic nephropathy and multiple myeloma-associated nephropathy), dehydration, congestive heart failure and use of concurrent nephrotoxic medication (including aminoglycosides and amphotericin B). Because contrast-induced nephropathy accounts for a significant increase in hospital-acquired renal failure, several strategies to prevent contrast-induced nephropathy are currently advocated, including use of alternative imaging techniques (for which contrast media are not needed), use of (the lowest possible amount of) iso-osmolar or low-osmolar contrast agents (instead of high-osmolar contrast agents), hyperhydration and forced diuresis. Administration of N-acetylcysteine, theophylline, or fenoldopam, sodium bicarbonate infusion, and periprocedural haemofiltration/haemodialysis have been investigated as preventive measures in recent years. This review addresses the literature on these newer strategies. Since only one (nonrandomized) study has been performed in intensive care unit patients, at present it is difficult to draw firm conclusions about preventive measures for contrast-induced nephropathy in the critically ill. Further studies are needed to determine the true role of these preventive measures in this group of patients who are at risk for contrast-induced nephropathy. Based on the available evidence, we advise administration of N-acetylcysteine, preferentially orally, or theophylline intravenously, next to hydration with bicarbonate solutions.

Prevention of Contrast Media–induced Nephrotoxicity after Angiographic Procedures

Contrast medium-induced nephrotoxicity (ie, contrast nephrotoxicity [CN]) remains an important complication of angiographic procedures. If administration of iodinated contrast medium is deemed necessary in patients at high risk of CN, volume expansion should be offered and the lowest possible dose of nonionic isosmolar dimeric or nonionic low-osmolar monomeric contrast medium should be used. Prophylactic administration of fenoldopam or acetylcysteine has not offered consistent protection against CN. Intravenous acetylcysteine could be considered in emergency situations. Recently, sodium bicarbonate infusion has been shown to reduce the risk of CN. Hemofiltration for several hours before and after contrast medium injection may offer good protection against CN in patients with advanced renal disease. Prophylactic hemodialysis does not offer any protection against CN.

In which patients should serum creatinine be measured before iodinated contrast medium administration?

Routine measurement of serum creatinine before injection of intravascular iodinated contrast material in all patients would be cumbersome and have an associated cost. There is doubt about whether serum creatinine should be measured routinely in all patients or selectively. The Contrast Media Safety Committee of the European Society of Urogenital Radiology decided to review the literature and draw up guidelines on this important practical issue. A literature search was carried out and summarized in a report. Based on the available information and discussions amongst the members of the Committee, guidelines were produced. The report and guidelines were discussed at the 11th European Symposium on Urogenital Radiology in Santiago de Compostela, Spain. The practice for identifying patients at risk of contrast medium induced nephropathy varies considerably from one institution to another. Patients at risk constitute only a small percentage of all cases referred for contrast enhanced imaging examination. However, it is important to identify them and take the necessary precautions. Recent serum creatinine level should be available in patients with an increased probability of a raised serum creatinine level (renal disease, renal surgery, proteinuria, diabetes mellitus, hypertension, gout, current intake of nephrotoxic drugs). A simple guideline has been produced.