Contrast media and the kidney: European Society of Urogenital Radiology (ESUR) guidelines

A prospective study to evaluate the depictability of the hepatic veins on abdominal contrast-enhanced CT in small children

BACKGROUND

The optimal conditions for abdominal contrast-enhanced (CE) CT, especially with respect to depiction of the hepatic veins (HVs), have not been well studied in small children.

OBJECTIVE

We compared the depiction of the HVs in small children using scan delay times of 50 s and 60 s and a power injector. The degree of contrast enhancement of the HVs according to body weight was also evaluated.

MATERIALS AND METHODS

A total of 50 CT studies in 31 children ages 2 days to 3 years 4 months (median 12 months) with a body weight less than 15 kg were prospectively evaluated. Nonionic contrast medium (300 mgI/ml) at a dose of 2 ml/kg and an injection rate calculated as (body weight in kilograms x 0.1) ml/s was injected through a 24-gauge intravenous catheter. Scan delay time was randomly chosen at 50 s or 60 s (25 times each). Subjective assessment of HV depiction was performed and the difference in CT number between the HV and hepatic parenchyma (HV-HP value) was calculated.

RESULTS

In all cases, subjective assessment of HV depiction was good and the HV-HP value was greater than 20 HU. The mean+/-SD HV-HP value was 47.7+/-13.2 HU. There were no differences in the mean HV-HP values between scan delay times of 50 s and 60 s (P=0.58).

CONCLUSION

For small children, this protocol for pediatric abdominal CECT resulted in good depiction of the HVs with no difference between scan delay times of 50 s and 60 s.

Pulmonary vein imaging with unenhanced three-dimensional balanced steady-state free precession MR angiography: initial clinical evaluation

PURPOSE

To determine whether unenhanced magnetic resonance (MR) angiography performed with a three-dimensional (3D) segmented steady-state free precession (SSFP) sequence would be an alternative to contrast material-enhanced MR angiography for evaluating pulmonary veins (PVs) prior to and following radiofrequency (RF) ablation for atrial fibrillation.

MATERIALS AND METHODS

MR angiographic examinations of PVs, performed in 20 patients (nine men, 11 women; mean age, 56.4 years +/- 12.7 [standard deviation]), were retrospectively reviewed according to an institutional review board-approved protocol. The number of PVs and their orthogonal measurements obtained from the 3D SSFP images were compared with those obtained from contrast-enhanced MR angiography. Signal-to-noise and contrast-to-noise ratios were also compared. Qualitative assessment of both techniques was performed by independent reviewers who scored the image quality (on a scale of 1 to 5) on the basis of PV conspicuity. The presence of cardiac and extracardiac pathologic indicators was also determined. Bland-Altman and Wilcoxon signed rank statistical analyses were performed.

RESULTS

The mean difference in PV diameter measurements between contrast-enhanced MR angiography and 3D SSFP was -0.02 cm +/- 0.25. Signal-to-noise and contrast-to-noise ratios were higher for 3D SSFP images than for contrast-enhanced MR angiograms. Qualitatively, there was no significant difference in PV conspicuity between the techniques. Noncardiac pathologic indicators were detected in 10 of 20 patients on 3D SSFP images but not on contrast-enhanced MR angiograms.

CONCLUSION

Unenhanced PV MR angiography performed by using a free-breathing 3D SSFP technique is as accurate as contrast-enhanced MR angiography for measuring PV diameter. This technique can be used for patients in whom contrast-enhanced computed tomographic or MR angiography is contraindicated and may be sufficient in all patients.

Contrast-induced nephropathy: are there differences between low osmolar and iso-osmolar iodinated contrast media?

It is acknowledged that high osmolar contrast media are more nephrotoxic than low (LOCM) or iso-osmolar contrast media (IOCM). However, it remains contentious whether the IOCM are less nephrotoxic in comparison with LOCM. This article reviews published clinical studies that investigated this issue and demonstrates there are no conclusive data to indicate that there is a definite difference in renal tolerance between LOCM and IOCM. All these agents are potentially nephrotoxic in patients with advanced renal impairment. In these patients the smallest possible dose of IOCM or LOCM should be used in addition to adequate hydration to minimize the risk of contrast nephropathy.

Acute phase reaction to gadolinium-DTPA in dialysis patients

BACKGROUND

Several late sequelae of the administration of gadolinium (Gd)-containing MRI contrast agents have been described in patients with advanced renal failure. In an observational series, we found a remarkable frequency of peracute reactions after administration of Gd-DTPA used for cardiovascular evaluation before renal transplantation.

METHODS

In a 26-month observational period, 13 of 136 haemodialyzed or CAPD patients exhibited onset of fever, chills and nausea within hours after administration of Gd-DTPA peracute. A minority showed persistent cessation of residual diuresis. We performed blood cultures in most patients and evaluated white blood cell (WBC) counts, eosinophils, CRP, heart rate and blood pressure.

RESULTS

Within an average of 12 h (range 12-36 h) after Gd administration, the 13 patients (9 males, 4 females; median age 61 years, range 47-79) developed consistent symptomatology with fever (median 39.0 degrees C, range 37.5-39.5), chills, malaise, hypotension, vomiting, dyspnoea-initially raising suspicion of septicaemia. Subsequent blood cultures on bacterial contamination of the injected product remained negative throughout; bacterial or endotoxin contamination of the reagent was excluded. Steroids were tried in the first two patients without a noticeable effect. In all subsequent patients, symptoms were attenuated during the first 5 h dialysis (F60HPS with 280 ml/min blood flow) and disappeared within 72 h. CRP levels remained markedly elevated up to 14 days. Lymphopenia was seen in all patients, and polymorphic neutrophils (PMN) remained normal. Two polyuric patients developed persistent anuria. After a median of 16 months, none of these patients developed nephrogenic systemic fibrosis.

CONCLUSION

This series with unusually severe acute phase reactions was caused by one specific preparation. Such peracute reactions may be relevant for the so-far largely unresolved pathogenesis of the skin reaction to some Gd products in end-stage renal disease (ESRD) patients. It remains unresolved whether the reaction observed with Gd-DTPA do in principle also occur with other Gd reagents.

Determination of split renal function by 3D reconstruction of CT angiograms: a comparison with gamma camera renography

OBJECTIVE

The objective of our study was to examine the correlation between CT-based and radionuclide renography-based measures of split renal function in a healthy population of live potential kidney donors using 3D models generated from CT angiography.

MATERIALS AND METHODS

The records of 173 renal donor candidates who had undergone CT and radionuclide renography between March 1, 2005, and February 28, 2006, were retrospectively evaluated; of those 173 patients, 152 met study inclusion criteria. A blinded investigator using 3D models that were created semiautomatically from the unenhanced, arterial, and excretory phase data made measurements of CT renal volumes and attenuations. The mean renal attenuation and volume were used to calculate the net accumulation of contrast material and split renal function for comparison with radionuclide renography. Split function from CT was calculated in the arterial and excretory phases as well as based on split renal volume and the Patlak method.

RESULTS

All four CT-based methods for the calculation of split renal function showed correlation with no significant difference from radionuclide renography (p > 0.05, Student's t test). Pearson's correlation coefficients varied from 0.36 to 0.63 (p < 0.001 for each). Difference scores revealed that the excretory and renal volume splits had the narrowest range and showed a linear, nonzero relationship to the renography splits. Bland-Altman analysis confirmed that the majority of difference scores between each CT method and the radionuclide renography were within the 95% CI of the differences.

CONCLUSION

Split renal function based on 3D CT models can provide a "one-stop" evaluation of both the anatomic and the functional characteristics of the kidneys of living potential kidney donors. The excretory phase data and the split renal volume data show the best correlation and the smallest difference scores compared with radionuclide renography data.

Prevalence of different gadolinium enhancement patterns in patients after heart transplantation

OBJECTIVES

Transplant coronary artery disease (TCAD) limits long-term survival after heart transplantation (HTX). We hypothesized that contrast-enhanced magnetic resonance imaging (CE-MRI) detects chronic TCAD-related myocardial infarctions (MIs), even in patients with angiographically classified mild TCAD.

BACKGROUND

Coronary angiography underestimates the TCAD-degree, subsequently missing occluded small coronary arteries and resulting MI. CE-MRI as a noninvasive imaging technique identifies infarct-typical MI and myocardial fibrosis.

METHODS

CE-MRI (gadolinium: 0.2 mmol/kg/bw) was performed in 53 HTX patients on a 1.5-T MRI scanner (Philips, Best, the Netherlands). Infarct-typical CE-MRI areas were classified as: I=<or=25%, II=25% to 50%, III=50% to 75% and IV=>or=75%. Infarct-atypical forms were divided into diffuse, spotted, intramural, and infero-septal. Coronary angiography results were reviewed qualitatively with the TCAD score (TCAD I=mild evidence; II=30% to 75%, III=>or=75% stenosis). Groups were compared with analysis of variance (statistically significant p values<or=0.05).

RESULTS

Infarct-typical CE-MRI was already present in TCAD I+II, increased significantly between groups (I=23%, II=33%, III=84%, p<0.05), and involved only single coronary territories in TCAD I but multiple vessels in TCAD II+III. Infarct-atypical CE-MRI was equally distributed across all TCAD stages (I=50% vs. II=58% vs. III=42%, p=NS) without relation to a coronary territory. Patients with only infarct-atypical CE-MRI were associated with significantly better left ventricular function compared with patients with infarct-typical or combined CE-MRI patterns (ejection fraction=66+/-6% vs. 45+/-16% or 60+/-13%; end-diastolic volume=139+/-32 ml vs. 148+/-27 ml or 164+/-43 ml; end-systolic volume=47+/-15 ml vs. 81+/-27 ml or 69+/-38 ml, p<or=0.05).

CONCLUSIONS

CE-MRI allows identification of silent MI in apparently event-free HTX patients and is able to disclose myocardial fibrosis already in patients with absent or mild angiographic TCAD. CE-MRI might be helpful to establish an earlier TCAD diagnosis and to intensify medical treatment. Future studies are necessary to test prognostic implications associated with CE-MRI patterns.

Intravascular iodinated contrast media and the anaesthetist

The use of intravascular iodinated contrast media (ICM) in radiological investigations is common. Increasingly, anaesthetists and intensivists are involved in the care of patients undergoing these investigations. Whilst the use of ICM is generally safe there are important adverse effects that need to be recognised and measures instigated to prevent or treat these effects. In patients at risk of developing adverse reactions it is important to consider alternative modes of imaging so that ICM can be avoided. Strategies for the prevention of ICM nephropathy should be considered in all patients receiving ICM. Currently intravascular volume expansion with 0.9% saline has the strongest evidence base. The use of isotonic sodium bicarbonate combined with N-acetylcysteine appears promising in providing further benefits. Although the use of N-acetylcysteine alone has not been shown to significantly reduce the incidence of ICM nephropathy it is cheap, has few adverse effects and it would seem reasonable to continue its use in conjunction with intravascular volume expansion. The routine use of corticosteroid and antihistamine premedication is not always effective in preventing general adverse reactions.

Radiologists’ knowledge and perceptions of the impact of contrast-induced nephropathy and its risk factors when performing computed tomography examinations: A survey of European radiologists

BACKGROUND

The past decade has seen a proliferation in the number of CT procedures. As increasing numbers of elderly patients with multiple comorbidities undergo contrast media (CM)-enhanced procedures, more patients are at risk for contrast-induced nephropathy (CIN).

OBJECTIVES

To understand whether radiologists are sufficiently aware of the incidence, impact and risk factors of CIN, and whether they are taking sufficient measures to prevent CIN among patients undergoing CT.

MATERIALS AND METHODS

A telephone or online survey was conducted in 2005 with 509 radiologists from 10 European countries. Participants had a minimum of 3 years' experience and performed at least 50 CT scans per week.

RESULTS

Most (88%) radiologists believed that CIN is an important issue. While 45% identify that a patient is experiencing CIN when the serum creatinine level increases >25% (0.5mg/dL) from baseline within 48h, the remainder used criteria that might lead to significant under-diagnosis. Most (72%) radiologists believed that CIN is associated with increased morbidity; 56% did not believe that it is associated with increased mortality. Most respondents agreed that pre-existing renal impairment (97%), dehydration (90%) and diabetes (89%) were risk factors for CIN; however, 26%, 30% and 46%, respectively, did not identify advanced age, CM dose or congestive cardiac failure as risk factors. Only 7% of radiologists thought they were always made aware of CIN associated with their cases and 28% never consulted a nephrologist to discuss patients at risk of CIN or who had developed CIN.

CONCLUSION

There is highly variable awareness of the definition, impact and risk factors for CIN among European radiologists. Data regarding the importance of CIN in CT are limited. Improved efforts are required to better educate radiologists and referring physicians and to institute appropriate protocols to identify at-risk patients and prevent CIN.

Contrast-induced nephropathy in patients with chronic kidney disease undergoing computed tomography: a double-blind comparison of iodixanol and iopamidol

BACKGROUND

Based on a single clinical trial, it has been suggested that the contrast agent iodixanol, which is isotonic to human plasma, may be less nephrotoxic than other nonionic contrast agents in renally impaired patients after intra-arterial injection. We compared the effects on renal function of iopamidol-370 injection (796 mOsm/kg) and iodixanol-320 (290 mOsm/kg) in patients with chronic kidney disease undergoing contrast-enhanced multidetector computed tomography (CE-MDCT) examinations using a multicenter, double-blind, randomized, parallel-group design.

METHODS

A total of 166 patients with stable moderate-to-severe chronic kidney disease (screening and baseline serum creatinine, SCr, > or =1.5 mg/dL and/or creatinine clearance, CrCl, < or =60 mL/min) who were undergoing CE-MDCT of the liver or peripheral arteries were randomized to receive equi-iodine IV doses (40 gI) of either iopamidol-370 (370 mgI/mL) or iodixanol-320 (320 mgI/mL) at 4 mL/s. SCr and CrCl were obtained at screening, baseline, and at 48-72 +/- 6 hours after dose (mean, 57.4 hours). Contrast-induced nephropathy (CIN) was defined as an absolute increase > or =0.5 mg/dL (44.2 micromol/L) and/or a relative increase in SCr > or =25% from baseline.

RESULTS

A total of 153 patients were included in the final analysis (13 patients excluded because of lack of follow-up, hemodialysis to remove contrast, average daily CrCl variation >1% at screening). The 2 study groups were comparable with regard to age, gender distribution, the presence of diabetes, concomitant medications, hydration, and contrast dose. Mean predose SCr was 1.6 +/- 0.4 mg/dL in both groups (P = 0.9). An absolute increase > or =0.5 mg/dL (44.2 micromol/L) in SCr was observed in none of the patients receiving iopamidol-370 and in 2.6% (2/76) of patients receiving iodixanol-320 (95% confidence interval -6.2, 1.0, P = 0.2). A relative increase > or =25% in SCr occurred in 4% (3/77) of patients receiving iopamidol-370 and in 4% (3/76) of the patients receiving iodixanol-320 (95% confidence interval -6.2, 6.1, P = 1.0).

CONCLUSION

The rate of CIN was similarly low in risk patients after intravenous administration of iopamidol-370 or iodixanol-320 for CE-MDCT.

Haematuria 2: Imaging investigations, management and follow up

Haematuria is a common complaint presenting to doctors in both primary and secondary care. It can be a sign of underlying urinary tract malignancy. Appropriate investigation and management should follow evidence-based practice and recognized guidelines, and subsequently lead to a rapid diagnosis.

Viscosity of contrast media perturbs renal hemodynamics

Contrast-induced nephropathy is a common cause of acute renal failure, and the mechanisms underlying this injury are not completely understood. We sought to determine how physicochemical properties of contrast media may contribute to kidney damage in rats. We administered contrast media of equivalent iodine concentrations but differing physiocochemical properties: the high-osmolality iopromide was compared to the high-viscosity iodixanol. In addition, the non-iodinated substances mannitol (equivalent osmolality to iopromide) and dextran (equivalent viscosity to iodixanol) were also studied. Both types of contrast media transiently increased renal and hindquarter blood flow. The high-osmolality agents iopromide and mannitol markedly increased urine production whereas iodixanol, which caused less diuresis, significantly enhanced urine viscosity. Only the high-viscosity agents iodixanol and dextran decreased renal medullary blood flux, erythrocyte concentration, and pO2. Moreover, iodixanol prolonged the tubuloglomerular feedback response and increased plasma creatinine levels to a greater extent than iopromide or dextran. Therefore, the viscosity of contrast media may play a significant role in contrast-induced nephropathy.

Incidence of Radiocontrast Nephropathy in Patients Undergoing Acute Stroke Computed Tomography Angiography

BACKGROUND AND PURPOSE

Minimal research has evaluated the renal safety of emergent computed tomography angiography (CTA) procedures, consecutive contrast medium application, and the long-term outcome in acute stroke patients. We investigated the incidence of contrast-induced renal impairment in these populations.

METHODS

We retrospectively reviewed patients with acute stroke syndrome who received a CTA of the brain with or without the neck within 24 hours from onset of symptoms. All creatinine results and additional conventional angiography findings were recorded. With a positive history of renal disease, contrast administration was delayed until creatinine results were available. Radiocontrast nephropathy (RCN) was defined as a >/=25% increase in serum creatinine from the baseline value up to 5 days after CTA.

RESULTS

Four hundred eighty-one patients were reviewed, and 224 met the inclusion criteria. There were 7 of 224 (3%) who fulfilled the criteria for RCN. A number of patients underwent emergent CTA without knowledge of their creatinine value; 2 of 93 (2%) developed RCN. There were 36 patients who received an additional digital subtraction angiogram, and none of these developed subsequent RCN. No patients required dialysis, and 9 of 68 (13%) had a >25% increase in their creatinine levels at a late (>30 days) follow-up.

CONCLUSIONS

Overall, these results illustrate that there is a low incidence of RCN in acute stroke patients undergoing emergency CTA.

The role of dialysis in contrast-induced nephropathy: doubts and certainties

Over past years, there has been a progressive increase in percutaneous endovascular procedures in patients with chronic renal disease, owing to the high incidence of vascular disease, particularly coronary artery disease, in this population. The use of contrast media may further worsen renal function in such patients, in some cases even accelerating the progression towards end-stage renal failure, and may increase patient morbidity and mortality. In this review, we discuss the role of dialysis in preventing contrast-induced nephropathy as well as present indications to its use in patients already on dialysis treatment undergoing diagnostic or therapeutic procedures with contrast medium injection.

Iodixanol

OBJECTIVE

To assess the risk of contrast-induced nephropathy in cancer patients with underlying renal insufficiency receiving the iso-osmolar intravenous contrast agent iodixanol for diagnostic computed tomography (CT) examinations.

METHODS

Institutional review board approval was obtained with waiver of informed consent. Our study was a retrospective evaluation comparing the incidence of contrast-induced nephropathy in consecutive patients with underlying renal insufficiency undergoing diagnostic CT examinations receiving iodixanol from November 2003 to June 2005 with a comparison group of patients with normal baseline renal function over the same period. Renal insufficiency was considered a serum creatinine level more than 1.2 mg/dL in females and more than 1.5 mg/dL in males. Contrast nephropathy was considered an absolute elevation of 0.5 mg/dL or 25% elevation in serum creatinine level.

RESULTS

In the group of patients receiving iodixanol with underlying renal insufficiency (189 patients), 9.0% developed contrast nephropathy (P = 0.015) with 4.8% of patients developing irreversible renal damage (P = 0.03). This compared with 4.9% of patients receiving iodixanol (185 patients) and 3.1% of patients receiving iohexol (194 patients) with normal baseline renal function developing contrast nephropathy (P = 0.38) with 3.2% of the iodixanol patients and 1.0% of the iohexol patients developing irreversible renal damage (P = 0.13).

CONCLUSIONS

The risk of contrast-induced nephropathy is significantly higher in patients with underlying renal insufficiency receiving iodixanol than that for patients with normal baseline renal function, but this should not serve as an absolute contraindication for these patients to receive intravenous iodinated contrast for diagnostic CT examinations particularly in patients with life-threatening clinical questions in which contrasted CT may provide valuable information.

Diabetes Care for Patients with Peripheral Arterial Disease

The number of diabetics will increase almost 70% in developed countries during the next 20 years: peripheral arterial disease is a common and costly complication. The incidence of cardiovascular disease (mortality and morbidity) due to atherosclerosis, is higher among patients with diabetes than in those without diabetes. Intensive management of diabetes, including glycaemic control, treatment of hypertension and dyslipidemia, as well as nonpharmacological interventions, decreases both micro- and macrovascular complications. Aspirin and clopidogrel have less antiplatelet effect in patients with diabetes. Metformin therapy is considered a risk factor for lactic acidosis if not withdrawn 2 days before angiography, but this risk is extremely low in patients with normal renal function. Peri-operative hyperglycaemia and large fluctuations in plasma glucose increase postoperative mortality and morbidity and careful measures are required to minimise these effects.

Prevention of contrast induced nephropathy: recommendations for the high risk patient undergoing cardiovascular procedures

Contrast induced nephropathy (CIN) is the third leading cause of hospital acquired renal failure and is associated with significant morbidity and mortality. Chronic kidney disease is the primary predisposing factor for CIN. As estimated glomerular filtration rate<60 ml/1.73 m2 represents significant renal dysfunction and defines patients at high risk. Modifiable risk factors for CIN include hydration status, the type and amount of contrast, use of concomitant nephrotoxic agents and recent contrast administration. The cornerstone of CIN prevention, in both the high and low risk patients, is adequate parenteral volume repletion. In the patient at increased risk for CIN it is often appropriate to withhold potentially nephrotoxic medications, and consider the use of n-acetylcysteine. In patients at increased risk for CIN the use of low or iso-osomolar contrast agents should be utilized and strategies employed to minimize contrast volume. In these patients serum creatinine should be obtained forty-eight hours post procedure and it is often appropriate to continue withholding medications such as metformin or non steroidal anti-inflammatories until renal function returns to normal.

One-molar gadolinium chelate (gadobutrol) as a contrast agent for CT angiography of the thoracic and abdominal aorta

The aim of our study was to evaluate the use of a 1-molar gadolinium chelate (gadobutrol) as an alternative contrast medium for computed tomography angiography (CTA) exams of the aorta. CTA exams of the thoracic and/or abdominal aorta were performed on 15 patients with contraindications for the use of iodine who were not suitable for magnetic resonance examinations. The exams were performed with a 16-detector row scanner, injecting a mean dose of 0.37 mmol Gd/kg of body weight at a flow rate of 4 ml/s. Creatinine levels were obtained prior to the exam in patients with impaired renal function, and 24 and 48 h afterwards. The mean attenuation values obtained in the middle ascending and middle descending thoracic aorta were 202.3 and 216.8, respectively. The mean HU values of the abdominal aorta were 210.4 at the level of the renal arteries and 186.8 in the aortic bifurcation. All the exams were considered diagnostically adequate. No significant increase in serum creatinine was observed 24 and 48 h after the exam. We believe that gadobutrol could be an alternative contrast medium for CTA exams with 16-detector row scanners in patients with contraindications for iodinated contrast medium.

Contrast-Induced Nephropathy

Contrast-induced nephropathy (CIN) is a well-recognized complication of radiographic contrast administration and is the third leading cause of hospital-acquired renal insufficiency. The use of contrast media is increasing, particularly in the area of endovascular therapy. Vascular interventionists need to be aware of strategies to reduce the risk of CIN. Numerous trials, meta-analyses, and expert guidelines for the prevention of CIN have been published between 1966 and 2006, but the majority of studies have been conducted on patients undergoing coronary interventions; few have involved vascular surgical population. The literature suggests that adequate hydration is essential in all patients due to receive contrast. No pharmacological agents have been shown to conclusively reduce the risk. Forced diuresis is harmful, and there is insufficient evidence to support routine use of hemodialysis or hemofiltration. Well conducted studies of other potential prophylactic techniques are needed in vascular populations.

Significance of zinc in nephrotoxicity of contrast media used in imaging diagnostics of the cardiovascular system

Nephrotoxicity is an undesirable reaction of contrast media used in X-ray or magnetic resonance diagnostics. In addition to a direct toxic effect on renal tubules, the hemodynamic factor is considered to be the main cause of kidney damage and malfunction. The factors that increase the probability of a nephrotoxic effect of contrast media include oldage, diabetes, arterial hypertension, circulatory system insufficiency, neoplastic diseases, and prior kidney damage. Decreased serum zinc is observed in all those conditions. In this article, the influence of contrast media on zinc homeostasis and the possibility of a nephrotoxic reaction caused by these agents is discussed.

Good MRI images: to Gad or not to Gad?

Gadolinium-based magnetic resonance imaging (MRI) contrast agents (Gad-CA) were formerly considered as alternatives to X-ray-employed iodinated media. Although originally thought to be nonnephrotoxic and proven to be nonhazardous in a healthy population, the Gad-CA safety issue is progressively more controversial in the high-risk group of end-stage renal disease (ESRD) patients. Recently, Gad-CAs have not only been blamed for harmless side effects such as dizziness or nausea but also for much more severe complications such as acute renal failure, pancreatitis, or even the development of so-called "nephrogenic systemic fibrosis" in patients with renal failure, culminating in the prohibition of gadodiamide (Omniscan) administration in ESRD patients and, due to renal-organ immaturity, in newborns and infants up to 1 year old. This editorial is written to give insights into the molecular structure of Gad-CAs as well as into the potential biochemical pathomechanisms underlying the aforementioned severe clinical manifestations. Furthermore, a review about the latest literature on Gad-CA nephrotoxicity is provided. Potential risk factors are mentioned and strategies to avoid deterioration of renal function are presented. Cases with Gad-CA-associated adverse events should be adequately documented and reported appropriately. MRI professionals should collaborate closely with their colleagues from other medical specialties to identify patients with adverse events.

[Contrast media and percutaneous coronary interventions]

Contrast media are widely used for percutaneous coronary interventions. Currently, about a dozen types of contrast media are available in France. On account of their overall safety, only low osmolar and isosmolar contrast media are used in practice. However, the appropriate use of contrast media remains difficult as accurate recommendations are lacking. Several doubts are still present regarding potential adverse effects of contrast media. Our review summarizes contrast media-related risks (hypersensitivity, arrhythmic risk, effects on coagulation and platelets, contrast media-induced nephrotoxicity) underlying mechanisms, prophylaxis strategies, and differences among contrast media. Many questions remain in this area and we need further prospective randomised trials.

Shift in imaging modalities of the urinary tract over a 25-year period and its impact on ionizing radiation doses given to patients

OBJECTIVES

To explore the shift in imaging modalities used when examining the urinary tract over the period 1979-2003 and to see how this shift, together with a radiation protection policy, have influenced the doses of ionizing radiation used.

MATERIAL AND METHODS

Activity reports from a department of radiology were reviewed. Relevant radiation dose estimates were obtained from the Norwegian Radiation Protection Authority.

RESULTS

Ultrasound (US) was introduced in 1983 and has been increasingly used since then. MRI was introduced in 1992 and has been used to some extent when examining the urinary tract. The use of i.v. pyelography decreased by 50% during the review period and the use of plain radiographs remained practically unchanged. The number of CT examinations increased until 1983, but decreased thereafter. The total number of examinations of the urinary tract has increased during the review period, but the radiation doses given have decreased.

CONCLUSIONS

The introduction of US and MRI, together with a radiation protection policy, have reduced the ionizing radiation doses given to this population, in spite of an increase in the total number of examinations of the urinary tract.

Contrast media and nephropathy: findings from systematic analysis and Food and Drug Administration reports of adverse effects

CONTEXT

Recent studies suggest differences in the incidence of contrast-induced nephropathy (CIN) among contrast media (CM).

OBJECTIVE

To determine whether there are significant differences among low-osmolality CM (LOCM) in the incidence of contrast-induced nephropathy (CIN), we reviewed published studies of CIN in renally impaired patients and conducted statistical data mining using databases of adverse events maintained by the U.S. Food and Drug Administration (FDA).

DATA SOURCES

A systematic literature search was performed for prospective, controlled, English language studies published in peer-reviewed journals that reported CIN rates in renally impaired patients after a specific LOCM. Databases searched were EMBASE, MEDLINE, Biosis Previews, Derwent Drug File, Pascal, and SciScearch Cited Ref Sci. For the FDA analysis, we used the SRS and AERS databases.

DATA SELECTION

Twenty-two studies reporting data in 3112 patients with renal impairment met the inclusion criteria. Most studies reported on the use of a pharmacologic intervention to prevent CIN. From the FDA databases, we evaluated 18 adverse event terms associated with renal injury or dysfunction after CM use.

DATA EXTRACTION

Data from 22 studies were entered into a database. A meta-regression analysis using a mixed effect model was performed. CM effect was adjusted by the following covariates: baseline patient characteristics (mean age, gender distribution) and risk factors (prevalence of diabetes mellitus, degree of renal impairment, CM volume), and the use of prophylactic drug treatments. Multiple disproportionality analyses (adjusted odds ratio, adjusted empirical Bayesian estimate, or Bayesian logistic regression) were performed on the FDA databases to estimate associations between 4 CM and 18 AE terms related to CIN.

DATA SYNTHESIS

Systematic analysis of clinical trials suggest the highest incidence of CIN occurs in patients receiving iohexol and the lowest incidence in patients receiving iopamidol, even when corrected for other CIN risk factors. Statistical data mining of FDA data also showed the highest association of CIN for iohexol and the lowest for iopamidol.

CONCLUSIONS

The risk of CIN was higher in patients receiving iohexol compared with patients receiving iopamidol. No significant differences were found comparing iohexol to other LOCMs, including iodixanol.

Epidemiology and prognostic implications of contrast-induced nephropathy

Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 0.5 mg/dL (44.2 mumol/L), or a 25% increase from the baseline value 48 hours after the procedure, is a common and potentially serious complication of the use of iodinated contrast media in patients at risk of acute renal injury. It is an important cause of hospital-acquired renal failure, responsible for approximately 11% of cases. CIN may be difficult to distinguish from cholesterol embolization, another cause of postprocedure renal impairment. The reported incidence of CIN varies depending on the patient population studied. The impact of postprocedural renal impairment on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention. CIN is associated with increased mortality both in hospital and at 1 year. A higher incidence of in-hospital and late cardiovascular events, as well as longer hospital stays, has been reported in patients developing CIN. In a small proportion of patients, CIN is severe enough to require dialysis, and these patients have a particularly poor prognosis. Many of the risk markers for CIN are also predictive of a worse prognosis.

Are Gadolinium-Based Contrast Media Nephrotoxic?: A Renal Biopsy Study

Gadolinium-based contrast media were originally introduced as alternatives to iodinated media for magnetic resonance imaging. Although originally thought to be nonnephrotoxic, gadolinium-based contrast media have recently been reported to be associated with acute renal failure; the mechanism and the underlying renal injury are not completely understood. We report what is, to our knowledge, the first renal biopsy in this context. A 56-year-old patient underwent 2 consecutive vascular imaging procedures in conjunction with gadolinium-based contrast medium administration. A few days later, the patient developed acute renal failure. A renal biopsy showed acute tubular cell injury including patchy tubular cell necrosis, tubular cell degeneration, and marked proliferation of tubular cells, together with mild interstitial edema and interstitial inflammation, but without significant glomerular or vascular changes. During supportive therapy, renal function was partially regained. This case emphasizes the potential nephrotoxicity of gadolinium-based contrast media and suggests that the nephrotoxicity is related to potentially reversible acute tubular cell injury.

Anästhesiologisches Management bei neuroendovaskulären Eingriffen

The endovascular treatment of diseases of intracranial and spinal vessels has become widely accepted in recent years. The patient is usually treated under general anesthesia and in choosing an appropriate anesthesia regimen and an optimized pre-interventional preparation, the anesthesiologist can influence the postinterventional result. The working environment in the angiography suite should address the requirements of a routine procedure and the necessities of complication management. Application of short-acting narcotics and relaxation of the patient if required, facilitate the intervention for both the neuroradiologist and the anesthesiologist. The patient should be supplied with everything needed before the intervention to avoid any waste of time in the case of an emergency (e.g., haemorrhage or fibrinolytic treatment). After the procedure the patient has to be monitored for at least 24 h. Peri-interventional and postinterventional complications, such as thrombo-embolism or hemorrhage, must be managed aggressively and consequently by the anesthesist to improve the postinterventional outcome. Therefore a close collaboration between the anesthesiologist and the neuroradiologist is essential.

Contrast medium-induced nephropathy: The pathophysiology

A widespread, rather general, definition of contrast-induced nephropathy (CIN) is an impairment in renal function occurring within 3 days following the intravascular administration of contrast media (CM) and the absence of an alternative aetiology. In spite of the vast clinical importance of CIN, its understanding and the pathophysiology behind CIN remain incomplete. Many studies have been performed; however, they have provided no widely accepted conclusion so far. Here the possible mechanisms underlying CIN are outlined, which span from altered rheological properties, perturbation of renal haemodynamics, regional hypoxia, auto-, and paracrine factors (adenosine, endothelin, reactive oxygen species) to direct cytotoxic effects. Although these potential mediators of CIN will be discussed separately, several factors may act in concert to perturb kidney function after exposure to contrast media. From the current knowledge of the mechanisms causing CIN, it is not possible to recommend a certain class of contrast media, except to avoid large doses of CM of the first generation. From a pathophysiological perspective, volume expansion is effective in avoiding CIN, since water permeability of the collecting ducts will decrease and enhance fluid excretion. Hence, CM in the distal portions of the tubular system is diluted, which implies reduced fluid viscosity and a lower risk of obstruction.

Contrast material-induced renal failure: an overview

The administration of iodinated contrast media (CM) is integral to many cardiovascular procedures. While it is clear that CM provide significant diagnostic benefit, there is some risk of contrast medium-related adverse events in a small percentage of patients. Potentially the most serious complication associated with the use of iodinated contrast agents is contrast-induced nephropathy (CIN). Most patients undergoing contrast-enhanced radiographic procedures are not at risk for CIN, however subjects with pre-existing renal insufficiency, diabetes mellitus, or cardiovascular disease receiving intra-arterial administrations of contrast material are at increased risk. Typically, patients with CIN will experience changes in serum creatinine 1-5 days following contrast exposure. While decrements in renal function are generally small and transient, some patients experience a more prolonged decrease and, in rare cases, require dialysis. More importantly, there is substantial literature documenting that patients with CIN after cardiac intervention experience greater morbidity (including prolonged hospitalization) and acute and 1-year mortality. The present article aims to briefly review the pathogenesis of CIN and reviews current opinion on how best to prevent CIN and manage at-risk patients.

[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.

The role of osmolality in the incidence of contrast-induced nephropathy: a systematic review of angiographic contrast media in high risk patients

BACKGROUND

The role of osmolality of contrast media (CM) in the pathogenesis of contrast-induced nephropathy (CIN) has been suggested by studies comparing high osmolality CM (>1500 mOsm/kg) with low-osmolality CM (550-850 mOsm/kg), and by the results of a recent comparison of a CM isotonic to plasma (iodixanol, 290 mOsm/kg) with a low-osmolality CM (iohexol, 844 mOsm/kg) in high-risk patients undergoing cardiac or peripheral angiography.

METHODS

Using prospectively defined search criteria, we performed a systematic overview of prospective, randomized, controlled studies of CIN in renally impaired patients receiving intra-arterial doses of iodixanol or low-osmolality, nonionic CM, and conducted a systematic review of the data from those studies to determine whether the osmolality of CM was predictive of CIN incidence.

RESULTS

Seventeen primary studies met the selection criteria, for a total of 1365 patients. Overall, the incidence of CIN was 16.8%. A multivariate logistic regression model showed that the risk of CIN is similar with the iso-osmolality iodixanol and the low-osmolality iopamidol (796 mOsm/kg). The risk of CIN was significantly lower with iodixanol and iopamidol compared to iohexol. The incidence of CIN with iohexol was also significantly higher than with iopamidol, despite their similar osmolalities.

CONCLUSION

These data suggest that factors other than osmolality play a significant role in the pathogenesis of CIN, at least for agents with osmolalities of 800 mOsm/kg or less.

Use of N-acetylcholine and sodium bicarbonate to protect renal transplant function during endovascular renal artery aneurysm exclusion

We describe the successful use of hydration with sodium bicarbonate and N-acetylcholine to prevent contrast-induced nephrophathy in a patient with a kidney transplant undergoing endovascular native renal artery aneurysm exclusion. The implications for surveillance studies for endovascular procedures are discussed.

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.

Multidetector computed tomography of the head in acute stroke: predictive value of different patterns of the dense artery sign revealed by maximum intensity projection reformations for location and extent of the infarcted area

Maximum intensity projections reconstructions from 2.5 mm unenhanced multidetector computed tomography axial slices were obtained from 49 patients within the first 6 h of anterior-circulation cerebral strokes to identify different patterns of the dense artery sign and their prognostic implications for location and extent of the infarcted areas. The dense artery sign was found in 67.3% of cases. Increased density of the whole M1 segment with extension to M2 of the middle cerebral artery was associated with a wider extension of cerebral infarcts in comparison to M1 segment alone or distal M1 and M2. A dense sylvian branch of the middle cerebral artery pattern was associated with a more restricted extension of infarct territory. We found 62.5% of patients without a demonstrable dense artery to have a limited peripheral cortical or capsulonuclear lesion. In patients with a 7-10 points on the Alberta Stroke Early Programme Computed Tomography Score and a dense proximal MCA in the first hours of ictus the mean decrease in the score between baseline and follow-up was 5.09+/-1.92 points. In conclusion, maximum intensity projections from thin-slice images can be quickly obtained from standard computed tomography datasets using a multidetector scanner and are useful in identifying and correctly localizing the dense artery sign, with prognostic implications for the entity of cerebral damage.

X-ray contrast media--an overview

X-ray contrast media are chemically inert drugs which are given intravascularly in very high amounts within a very short time period. Although they are regarded as relatively safe drugs, adverse reactions can occur: these are normally divided into immediate and delayed reactions. The latter appear hours to days after injection. Immediate reactions have been drastically reduced since the introduction of non-ionic monomers and non-ionic dimers. However, the delayed reactions still occur in a frequency of 1-3% in X-ray contrast media exposed patients. The majority of these reactions are mild and manifest as skin eruption, but severe reactions can also occur. Further improvement of the safety of these drugs is only possible with a better understanding of etiologies behind the observed adverse reactions.

Contrast nephropathy, pathophysiology and prevention

Contrast nephropathy is a common cause of iatrogenic acute renal failure. Its incidence rises with the growing use of intra-arterial contrast in diagnostic and interventional procedures. Aim of the present review is to summarize the knowledge about pathophysiology and prevention. Nephrotoxicity is related to osmolality, dose and route of the contrast and only occurs in synergy with other factors, such as previous renal impairment and cardiovascular disease. With an interplay of these factors, contrast nephropathy has an impact on morbidity and mortality. Pathophysiological mechanisms are intrarenal vasoconstriction, leading to medullary ischemia, direct cytotoxicity, oxidative tissue damage and apoptosis. Several measures are of proven benefit in patients at risk. Among them are discontinuation of potentially nephrotoxic drugs, hydration, preferably with isotonic sodium bicarbonate, use of low osmolal contrast, oral or intravenous N-acetylcysteine and intravenous theophylline. In patients with severe cardiac and renal dysfunction undergoing cardiac interventions, periprocedural hemofiltration may be considered.