A closer look at radiocontrast-induced nephropathy

Adriamycin Nephrosis and Contrast Media

Urine profiles (albumin, glucose, NAG, LDH, GGT and sodium) were followed for 9 days after intravenous injection of either diatrizoate, iohexol, or saline in 27 Wistar rats with nephrosis induced by Adriamycin 42 days before. Another 9 rats exposed to neither Adriamycin nor contrast media served as controls. None of the contrast media caused further increased albuminuria of significance, whereas both induced significantly increased excretion of all 5 tubular components. The excretion of NAG and sodium was significantly higher following diatrizoate than following iohexol. From 24 h post injection there was no significantly greater excretion of any of the components after either diatrizoate or iohexol than after saline among the rats given Adriamycin. At the end of day 9 after contrast medium injection neither serum sodium, potassium, glucose, urea, creatinine, nor albumin revealed any contrast media related changes. Kidney histology showed quantitatively larger lesions in kidneys exposed to Adriamycin and contrast media than in kidneys exposed to Adriamycin and saline. There were no differences between the two contrast media groups. It is thus concluded, that both high osmolar ionic and low osmolar non-ionic contrast media cause temporary tubular dysfunction but no further glomerular dysfunction in rats with nephrosis induced by Adriamycin. The histologic findings indicate that both media may worsen non-reversible renal lesions.

Low Sodium Diet, Indomethacin, and Contrast Media

Urine profiles were followed for 3 or 9 days after intravenous injection of diatrizoate, iohexol, or saline in 30 adult Wistar rats, which received a low sodium diet for 14 days, and indomethacin intravenously 2 hours and immediately before contrast medium or saline injection. A control group of 10 rats, which also received low sodium diet, got saline alone and no indomethacin or contrast medium. Diatrizoate increased albuminuria during the first 22 hours after its injection whereas iohexol did not have any significant effect on albuminuria. Both contrast media caused tubular dysfunction, but there was significant difference between them during the first 2 hours after injection. Compared to the effect of saline, iohexol but not diatrizoate caused increased excretion of lactate dehydrogenase and N-acetyl-beta-glucosaminidase for 2 days. Iodine measurements showed delayed excretion of both media. Light microscopy showed focal location of dilated tubular profiles with hydrophia, which were only present in kidneys exposed to contrast media. It is concluded that in rats fed on a low sodium diet administration of indomethacin in relation to iohexol has a greater tubular cell effect than diatrizoate, which in turn has a greater effect on the glomerular permeability. The excretion of both media is delayed.

Nephrotoxicity of Cyclosporin a and Contrast Media

Urine profiles (albumin, glucose, NAG, LDH, GGT and sodium) were followed for 22 h or 8 days after intravenous injection of diatrizoate, iohexol or saline in 30 adult Wistar rats in which nephrotoxicity was induced by daily peroral administration of 25 mg/kg body weight cyclosporin A over a 14-day period. Another 10 rats which had the vehicle of the cyclosporin A solution (placebo) and saline injected intravenously served as controls. The effect of iohexol and saline on the albumin excretion was similar, whereas diatrizoate increased it significantly. Both contrast media caused significantly increased excretion of all three enzymes. The contrast media had no effect on the excretion of glucose and sodium. Except for the fact that the excretion of NAG was significantly higher following iohexol than following diatrizoate 24 to 46 h after injection no significant differences between the two media were found from 24 h after injection among the rats given cyclosporin A. No contrast medium related changes were found by light microscopy of the kidneys. Neither iohexol nor diatrizoate potentiate acute cyclosporin A nephrotoxcity.

Fused magnetic resonance angiography and 2D fluoroscopic visualization for endovascular intracranial neuronavigation

Advanced transluminal neurovascular navigation is an indispensable image-guided method that allows for real-time navigation of endovascular material in critical neurovascular settings. Thus far, it has been primarily based on 2D and 3D angiography, burdening the patient with a relatively high level of iodinated contrast. However, in the patients with renal insufficiency, this method is no longer tolerable due to the contrast load. The authors present a novel image guidance technique based on periprocedural fluoroscopic images fused with a preinterventionally acquired MRI data set. The technique is illustrated in a case in which the fused image combination was used for endovascular treatment of a giant cerebral aneurysm.

Effect of low-osmolar contrast medium iopromide and iso-osmolar iodixanol on DNA fragmentation in renal tubular cell culture

BACKGROUND

Intravascular administration of iodinated contrast media continues to be a common cause of hospital-acquired acute kidney injury. Accumulating evidence suggests that radiocontrast agent-induced nephrotoxicity is associated with increased oxidative stress, which leads to renal tissue damage with DNA fragmentation. We therefore tested whether an iso-osmolar contrast medium (iodixanol) causes less oxidative DNA damage to renal tubular cells than a low-osmolar contrast medium (iopromide).

METHODS

HK-2 cells (human proximal renal tubular cell line) were incubated at different time points (10 min-2 h) with increasing concentrations (20-120 mg/ml iodine) of iodixanol or of iopromide. Oxidative DNA damage to renal tubular cells was measured by alkaline comet assay (single-cell gel electrophoresis).

RESULTS

Both iso- and low-osmolar contrast agents induced time- and concentration-dependent DNA fragmentation. DNA fragmentation was maximal at 2 h with 120 mg/ml iodine for iopromide (32 ± 27 tail moments) and iodixanol (46 ± 41 tail moments); both were significantly different from the control value with 3.15 ± 1.6 tail moments (Student's t test; p < 0.001). After 1 and 2 h and for all concentrations, iodixanol produced significantly higher DNA fragmentation than iopromide (ANOVA for 1 h p = 0.039 and 2 h p = 0.025, respectively).

CONCLUSION

We were able to demonstrate for the first time that an iso-osmolar contrast medium induced even greater oxidative stress and DNA damage than a low-osmolar agent in HK-2 cells. This could provide an explanation for the nephrotoxicity that also is observed with iodixanol in clinical practice.

Association of serum bilirubin with contrast-induced nephropathy and future cardiovascular events in patients undergoing coronary intervention

Objectives

Enhanced reactive oxygen species formation within the kidney following the administration of contrast media may play a key role in the development of contrast-induced nephropathy (CIN). Bilirubin has emerged as an important endogenous antioxidant molecule. This study was undertaken to determine whether bilirubin is associated with CIN and future cardiovascular events in patients undergoing coronary intervention.

Methods

Totally, 544 consecutive patients received coronary intervention were enrolled. All patients were followed up for at least 3 years or until the occurrence of a major event. The primary endpoint was CIN, defined as a rise in serum creatinine (SCr) of 0.5 mg/dl or a 25% increase from the baseline value within 48 hours after the procedure. The secondary endpoint was the combined occurrence of major adverse cardiovascular events (MACE), including death, nonfatal myocardial infarction, and ischemic stroke.

Results

Overall, CIN occurred in 85 (15.6%) patients. All patients were stratified into 3 groups (low/normal/high) according to the serum bilirubin levels. In a multivariate logistic analysis, the odds ratio for CIN with low-bilirubin levels relative to high-bilirubin levels was 11.82 (95% CI, 3.25–43.03). By Cox regression analysis, serum bilirubin levels was an independent predictor of MACE in patients undergoing coronary intervention (low vs. high hazard ratio 2.26; 95% CI, 1.05–4.90).

Conclusions

CIN is a serious complication of coronary intervention. Higher serum bilirubin concentrations were associated with lower risk of CIN and fewer cardiovascular events. The development of interventions that promote bilirubin levels may be a potential target to reduce CIN and future MACE in patients undergoing coronary intervention.

Ischemic preconditioning for prevention of contrast medium-induced nephropathy: randomized pilot RenPro Trial (Renal Protection Trial)

BACKGROUND

Contrast medium-induced acute kidney injury is associated with substantial morbidity and mortality. The underlying mechanism has been attributed in part to ischemic kidney injury. The aim of this randomized, double-blind, sham-controlled trial was to assess the impact of remote ischemic preconditioning on contrast medium-induced acute kidney injury.

METHODS AND RESULTS

Patients with impaired renal function (serum creatinine >1.4 mg/dL or estimated glomerular filtration rate <60 mL · min(-1) · 1.73 m(-2)) undergoing elective coronary angiography were randomized in a 1:1 ratio to standard care with (n=50) or without ischemic preconditioning (n=50; intermittent arm ischemia through 4 cycles of 5-minute inflation and 5-minute deflation of a blood pressure cuff). Overall, both study groups were at high risk of developing contrast medium-induced acute kidney injury according to the Mehran risk score. The primary end point was the incidence of contrast medium-induced kidney injury, defined as an increase in serum creatinine ≥25% or ≥0.5 mg/dL above baseline at 48 hours after contrast medium exposure. Contrast medium-induced acute kidney injury occurred in 26 patients (26%), 20 (40%) in the control group and 6 (12%) in the remote ischemic preconditioning group (odds ratio, 0.21; 95% confidence interval, 0.07-0.57; P=0.002). No major adverse events were related to remote ischemic preconditioning.

CONCLUSIONS

Remote ischemic preconditioning before contrast medium use prevents contrast medium-induced acute kidney injury in high-risk patients. Our findings merit a larger trial to establish the effect of remote ischemic preconditioning on clinical outcomes.

CLINICAL TRIAL REGISTRATION

URL: http://www.germanctr.de. Unique identifier: U1111-1118-8098.

Iodixanol, constriction of medullary descending vasa recta, and risk for contrast medium-induced nephropathy

PURPOSE

To determine whether a type of contrast medium (CM), iodixanol, modifies outer medullary descending vasa recta (DVR) vasoreactivity and nitric oxide (NO) production in isolated microperfused DVR.

MATERIALS AND METHODS

Animal handling conformed to the Animal Care Committee Guidelines of all participating institutions. Single specimens of DVR were isolated from rats and perfused with a buffered solution containing iodixanol. A concentration of 23 mg of iodine per milliliter was chosen to mimic that expected to be used in usual examinations in humans. Luminal diameter was determined by using video microscopy, and NO was measured by using fluorescent techniques.

RESULTS

Iodixanol led to 52% reduction of DVR luminal diameter, a narrowing that might interfere with passage of erythrocytes in vivo. Vasoconstriction induced by angiotensin II was enhanced by iodixanol. Moreover, iodixanol decreased NO bioavailability by more than 82%. Use of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (a superoxide dismutase mimetic) prevented both vasoconstriction with iodixanol alone and increased constriction with angiotensin II caused by CM.

CONCLUSION

Iodixanol in doses typically used for coronary interventions constricts DVR, intensifies angiotensin II-induced constriction, and reduces bioavailability of NO. CM-induced nephropathy may be related to these events and scavenging of reactive oxygen species might exert a therapeutic benefit by preventing the adverse effects that a CM has on medullary perfusion.

Calpain 10 is required for cell viability and is decreased in the aging kidney

Aging is associated with abnormalities in kidney function, but the exact mechanisms are unknown. We examined calpains 1, 2, and 10 protein levels in kidneys from rats, mice, and humans of various ages and determined whether calpain 10 is required for cell viability. Calpain 10 protein expression decreased in the kidney, but not in the liver, of aging Fischer 344 rats, and this decrease was attenuated with caloric restriction. There was no change in calpains 1 or 2 levels in the kidney or liver in control and caloric-restricted aging rats. Aging mice also exhibited decreased calpain 10 protein levels. Calpain 10 protein and mRNA levels decreased linearly in human kidney samples with age in the absence of changes in calpains 1 or 2. Our laboratory previously found calpain 10 to be expressed in both the cytosol and mitochondria of rabbit renal proximal tubular cells (RPTC). Adenoviral-delivered shRNA to rabbit RPTC decreased mitochondrial calpain 10 expression below detectable levels by 3 days while cytosolic calpain 10 levels remained unchanged at 3 days and decreased to approximately 20% of control by 5 days. Knockdown of mitochondrial calpain 10 resulted in nuclear condensation and cleaved procaspase 3, markers of apoptosis. In summary, mitochondrial calpain 10 is required for cell viability and calpain 10 levels specifically decrease in aging rat, mice, and human kidney tissues when renal function decreases, suggesting that calpain 10 is required for renal function and is a biomarker of the aging kidney.

Does gadolinium-based angiography protect against contrast-induced nephropathy?: a systematic review of the literature

We evaluated the incidence of contrast-induced nephropathy (CIN) in patients exposed to gadolinium for diagnostic or therapeutic procedures.

BACKGROUND

CIN with iodinated contrast agents is a leading cause of acute renal failure. Gadolinium is often used as an alternative to iodinated contrast in patients at increased risk of CIN. The safety of gadolinium in patients at increased risk of CIN has not been established.

METHODS AND RESULTS

The authors performed a systematic review by searching MEDLINE, ISI Web of Knowledge, Current Contents, Embase, and the Cochrane Central Register of Controlled Trials to identify relevant studies evaluating gadolinium and its associated incidence of CIN. They identified 17 studies that reported both favorable and negative results with regard to the association of gadolinium and CIN. The differences in the results appeared to be dose related. When gadolinium was used in doses of 0.4 mmol/kg or higher, there appeared to be an increased incidence of ARF particularly in patients with preexisting renal insufficiency.

CONCLUSIONS

Although the evidence base is limited, gadolinium does not appear to be safer than iodinated contrast in patients at risk of CIN. Given the lack of randomized data to support its safety, gadolinium in lieu of iso-osmolar iodinated contrast cannot be advocated in patients at high risk of contrast nephropathy.

Promoter methylation is associated with the age-dependent loss of N-cadherin in the rat kidney

The cadherins are cell adhesion molecules required for cellular homeostasis, and N-cadherin is the predominant cadherin expressed in proximal tubular epithelial cells in humans and rats. Our laboratory previously reported an age-dependent decrease in renal N-cadherin expression; the levels of N-cadherin mRNA and protein expression decreased in parallel, implicating a transcriptional mechanism in the age-dependent loss of expression (19). In this study, we examined the hypothesis that promoter hypermethylation underlies the loss of N-cadherin expression in aging rat kidney. We cloned the 5' flanking region of the rat N-cadherin gene and observed basic promoter activity in a 3,992-bp region localized immediately upstream of the ATG start site. Nucleotide analysis revealed 87% identity with the human N-cadherin minimal promoter region. Consistent with a role for regulation by DNA methylation, we found that a dense CpG island, which spans 1,104 bp (-1,158 to -55), flanks the rat N-cadherin gene; a similar CpG profile was found in the human N-cadherin 5' flanking region. Methylation-specific PCR analysis demonstrated that the promoter region of N-cadherin is heavily methylated in aged, but not young, rat kidney. Interestingly, the promoter is not methylated in age-matched, calorically restricted animals. In contrast, the promoter region is not methylated in either young or aged rat liver; this corresponds to the finding that aging is not associated with decreased N-cadherin expression in the liver. In addition, N-cadherin expression is markedly induced in NRK-52E cells treated with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine, further suggesting that methylation at CpG in the promoter region may underlie the age-dependent decrease in renal N-cadherin expression.

Contrast-induced nephropathy

Interventional radiological procedures involving anaesthesia are generally increasing. Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 44 micromol litre(-1) (0.5 mg dl(-1)) or a 25% increase from the baseline value 48 h after intravascular injection of contrast media, 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, may be a difficult differential diagnosis and the incidence does not appear to have changed over the last few decades. In the general population, the incidence of CIN is estimated to be 1-2%. However, the risk for developing CIN may be as high as 50% in some patient subgroups, such as those with diabetes mellitus and pre-existing renal impairment. The impact of CIN on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention where it is associated with increased mortality both in hospital and at 1 yr. As treatment is limited to supportive measures while awaiting the resolution of the renal impairment, emphasis needs to be directed at prevention.

Emerging techniques: Whole-body screening and staging with MRI

Strategies for screening or tumor staging include various modalities such as plain radiography, computed tomography (CT), MRI, and ultrasound. Technical innovations have created the feasibility to use MRI to image the entire body in a relatively short time-period. Whole-body MRI may play a potentially important role in evaluating for cancer or vascular disease. This article describes the rationale for using MRI to display the entire body, the techniques employed in whole-body MRI, possibilities and limitations, and summarizes first clinical results for screening and staging purposes.

Prehydration Alone is Sufficient to Prevent Contrast-induced Nephropathy after Day-only Angiography Procedures—A Randomised Controlled Trial

BACKGROUND

Contrast agents used in angiography procedures for patients with cardiovascular disease are known to cause contrast-induced nephropathy (CIN), which may be partially due to the production of nephrotoxic oxygen-free radicals. It is uncertain whether administration of intravenous (IV) anti-oxidant, N-acetylcysteine (NAC), can prevent reduction in renal function and whether this is a cost-effective approach.

METHODS

Sixty-five day-only patients with renal impairment (mean serum creatinine concentration 0.16+/-0.03 mmol/l) due to undergo coronary or peripheral angiography and/or stenting were randomly assigned to IV NAC 300 or 600 mg immediately before and after the procedure or IV fluid alone.

RESULTS

Of the 60 patients with complete data, none had acute CIN (increase in serum creatinine concentration > or = 0.044 mmol/l, 48 h after administration of contrast agent). Eight patients (13%) have demonstrated an increase in their serum creatinine concentration > or = 0.044 mmol/l 30 days after administration of contrast agent: 2/19 (11%) in the control group, 2/21 (10%) in the 600 mg NAC group and 4/20 (20%) the 300 mg NAC group (p = 0.66). The mean volumes of contrast agent used and prehydration given for each of the three groups did not differ significantly (p > 0.83). There was significant improvement in creatinine clearance within each group from baseline to 30 days (p < or = 0.03), but no significant difference between the groups at 48 h and 30 days (p > or = 0.43). Considering the cost of NAC and its administration, we estimate that this would translate to a saving of dollar 26,637 per annum.

CONCLUSION

For day-stay patients with mild-to-moderate chronic renal impairment undergoing angiography and/or intervention, prehydration alone is less complicated and more cost-effective than a combination of IV NAC (at doses used) and hydration.

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.

Whole-body magnetic resonance imaging

Whole-body magnetic resonance imaging is a fast and accurate modality for the detection of disease throughout the entire body. Technical improvements including the availability of different high image quality MR sequences, the remote movement of the imaging table, and the use of specialized surface coils have rendered whole-body screening with MRI a feasible method. In this article we describe underlying techniques and report on first clinical experiences of whole-body magnetic resonance imaging as a staging and screening method. Furthermore, advantages and limitations compared with whole-body imaging based on computed tomography are discussed.

Loss of N-cadherin and alpha-catenin in the proximal tubules of aging male Fischer 344 rats

Aging is associated with a loss of renal reserve, and increased sensitivity to either xenobiotic or physiologic insult. Given the critical role of the cadherin/catenin complex in establishing and maintaining the integrity and polarity of tubular epithelial cells, it was hypothesized that aging was associated with alterations in renal cadherin/catenin complexes. Histological assessment of aged (24 months) kidneys harvested from male Fischer 344 rats demonstrates mild degeneration of proximal tubules, multifocal chronic lymphocytic infiltration, moderate development of protein casts inside tubules, and tubular dilatation or degeneration. Western blot analysis revealed that N-cadherin protein expression is not constant over 24 months. N-cadherin expression increased from 4 to 9 months, with peak levels at 9 and 13 months. A decrease in expression was seen at 19 months and an almost complete loss of expression was seen at 24 months. In contrast, the expression of E- and Ksp-cadherin was constant over 24 months. A loss of alpha-catenin at was seen at 19 and 24 months in the absence of changes in beta-, gamma-, and p120-catenin. This pattern of N-cadherin expression (increase followed by decrease) was confirmed by real-time PCR analysis, which demonstrated a similar pattern as the Western blot, suggesting that the loss of N-cadherin protein was due to decreased gene expression. The loss of N-cadherin was specific for the kidney, as no changes in N-cadherin expression in the liver, brain, or testes were seen during aging. The conclusion that loss of N-cadherin expression is a critical component of the renal dysfunction associated with aging is supported by the finding that caloric restriction attenuates the loss of N-cadherin, as well as the finding that a significant loss of N-cadherin is seen in the kidneys of ZDF x SHHF rats, a genetic model of end-stage renal disease. Cadherin and catenin expression was further analyzed by immunofluorescence. A significant loss of staining of both N-cadherin and alpha-catenin was seen in the proximal tubules of rats at 24 months. Interestingly, this corresponded with delocalization of the alpha-1 subunit of the Na+K+-ATPase, i.e. aberrant staining on cell-cell borders and some indication of apical staining in proximal tubules. Taken together, these data suggest that aging is associated with decreased expression of N-cadherin and alpha-catenin and is associated with a loss of cell polarity.

Renal Effects of CO2 and Iodinated Contrast Media in Patients Undergoing Renovascular Intervention: A Prospective, Randomized Study

PURPOSE

CO2 gas has been proposed for use instead of iodinated contrast media in angiographic examinations in patients at risk of developing renal failure from contrast media. The influence of intraarterial injection of CO2 with small added amounts of ioxaglate (200 mgI/mL) or ioxaglate alone on renal function in patients with suspected renal artery stenosis was studied in a prospective, randomized study.

MATERIALS AND METHODS

One hundred twenty-three patients underwent renovascular intervention (n = 83) and/or renal angiography (n = 40) for suspected renal artery stenosis. Patients with a serum creatinine concentration less than 200 micromol/L (n = 82) were randomized prospectively to receive CO2 with small added amounts of ioxaglate (n = 37) or only ioxaglate (n = 45). Patients with serum creatinine levels greater than 200 micromol/L (n = 41) were not randomized and initially received CO2. Serum creatinine concentrations were measured within 1 day before and 1 day, 2 days, and 2-3 weeks after the procedure.

RESULTS

The amount of injected CO2 did not relate to an increase in serum creatinine level. In the randomized groups, and also when the whole patient sample was considered, the amount of injected iodine was significantly correlated (P = .011) with an increase in serum creatinine level and a decrease in estimated creatinine clearance after 2 days. Among the randomized patients, one in the CO2 group and three in the ioxaglate group had a more than 25% increase in serum creatinine level within the first 2 days after the intervention.

CONCLUSION

The risk of impairment of renal function is lower after injection of CO2 with small amounts of added ioxaglate compared with injection of a larger amount of ioxaglate alone. The larger the amount of administered iodinated contrast medium, the greater the risk of development of renal failure.

The cytotoxicity of iodinated radiocontrast agents on renal cells in vitro

A deterioration of renal function is one preoccupying complication of iodinated radiocontrast agents in clinical practice. These compounds have direct toxic effects on renal cells, which are only in part related to their physicochemical properties. The hyperosmolal monomeric ionic radiocontrast agents, like diatrizoate, have the highest toxicity, whereas renal cells are less affected by (nonionic) compounds with reduced osmolality. The toxic effects include cellular energy failure, a disruption of calcium homeostasis, a disturbance of tubular cell polarity and programmed cell death (apoptosis). The molecular mechanisms of the direct cytotoxicity are still unclear, although oxidative stress has been implicated. Radiocontrast cytotoxicity has been demonstrated in glomerular mesangial cells and in renal epithelial cells in vitro. In vivo, the direct cellular toxicity of radiocontrast agents is compounded with alterations in blood flow and/or viscosity, ultimately resulting in renal medullary hypoxia, which is a hallmark feature of the complex clinical syndrome of radiocontrast nephropathy.

Free reactive oxygen species and nephrotoxicity of contrast agents

BACKGROUND

The nephrotoxicity induced by contrast media remains a serious clinical problem, and the underlying mechanism has not been completely understood. Experimental and clinical investigations suggest that reactive oxygen species (ROS) are critical determinants of radiocontrast nephropathy (RCN), and that antioxidants can prevent this damage.

METHODS

Cultured human proximal renal tubule cells (HK-2) were exposed to hydrogen peroxide (H2O2) at different concentrations. H2O2-induced tubular DNA damage was examined in the presence of the antioxidant MESNA (sodium-2-mercaptoethane sulphonate). The induction of DNA damage was measured with the alkaline comet assay (single cell gel electrophoresis). We also studied 12 patients with stable renal impairment (median baseline creatinine 296 micromol/l; range: 203-495 micromol/l) undergoing cardiac catheterization/intervention prospectively. Patients received 800 mg MESNA intravenously 30 min before exposure to the contrast agent in addition to 0.9% saline hydration.

RESULTS

In the cell cultures, oxidative stress on HK-2 cells induced increased DNA migration in the comet assay. Treatment of tubular cells with the antioxidant MESNA prior to the addition of H2O2 significantly reduced DNA migration in the comet assay. In the clinical study, treatment of the patients with MESNA prevented the adverse renal effect of contrast media (median serum creatinine 293; range: 187-433 micromol/l) 48 h after coronary angiography/intervention.

CONCLUSION

Both the in vivo and the in vitro studies suggest that the ROS-mediated renal injury could be inhibited by a potent antioxidant such as MESNA.

Contrast medium-induced acute renal failure and cholesterol embolism after radiological procedures: incidence, risk factors, and compliance with recommendations

BACKGROUND: After radiological procedures, the incidence of acute renal failure varies greatly, and cholesterol embolism may not always be recognized. Little, if anything, is known about whether recommendations for the prevention of either complication are correctly implemented. METHODS: We performed a prospective epidemiological study in a large population (n=809) of consecutive inpatients in a university hospital. The patients were monitored for risk factors, ongoing medications, and details of preventive measures and of radiological procedures. Contrast nephropathy was defined as a 25% rise in serum creatinine. Cholesterol embolism was defined by the presence of two typical signs. We analyzed the incidence, risk factors, and prevention of contrast nephropathy and cholesterol embolism. RESULTS: The most frequent procedure that our patients underwent was cardiac angiography (50%). The incidence of contrast nephropathy was 7%. We confirmed the classical risk factors (diabetes, dose of contrast medium, and renal insufficiency) and added potentially nephrotoxic medications as an independent risk factor. Fluid therapy, commonly proposed in high-risk patients, was adequately carried out in only 12% of patients. The incidence of cholesterol embolism was 4%, with 10% renal involvement. Arteriosclerosis and renal insufficiency were risk factors, but anticoagulation therapy was not. CONCLUSION: Adequate fluid therapy and discontinuation of nephrotoxic medications should be more systematically implemented in the prevention of contrast nephropathy. Recognition of cholesterol embolism is crucial.

Radiocontrast-induced renal tubular cell apoptosis: hypertonic versus oxidative stress

RATIONALE AND OBJECTIVES

Radiocontrast-induced nephropathy (RCIN) is a major complication of intravascular radiocontrast administration. Renal tubular cell apoptosis is a feature of RCIN, which is related to hypertonicity of contrast agents. Because a hyperosmolal extracellular environment induces oxidative stress via reactive oxygen species, we tested the hypothesis that antioxidants decrease hypertonicity-induced apoptosis of renal epithelial cells. We analyzed the effects of the antioxidants N-acetylcysteine (NAC) and taurine on hypertonicity-induced apoptosis of renal epithelial cells in vitro.

METHODS

Madin Darby Canine Kidney (MDCK) cells were incubated with the highly hyperosmolal, ionic radiocontrast agent diatrizoate (20% vol/vol, 6 hours) or with equally hyperosmolal (640 mOsm/kg) NaCl solutions. DNA fragmentation, which is a hallmark feature of apoptosis, was assessed quantitatively using flow cytometry after propidium iodide staining and qualitatively using agarose gel electrophoresis.

RESULTS

Both diatrizoate and NaCl induced DNA fragmentation in MDCK cells. Taurine (10 mmol/L) reduced DNA degradation in both diatrizoate- [79.5 +/- 2.3% versus 72.2 +/- 3.0%; P = 0.0088] and NaCl- [49.5 +/- 4.0% versus 39.4 +/- 1.0%; P = 0.0271] treated cells. In contrast, NAC (10 mmol/L) failed to reduce the DNA breakdown in this model of hypertonicity-induced renal tubular cell apoptosis.

CONCLUSIONS

The radiocontrast/hypertonicity-induced DNA fragmentation of MDCK cells is attenuated by taurine but not by NAC. Because both agents are antioxidants, the antioxidant property is not sufficient for the observed cytoprotective effect. Hence, the antiapoptotic effect of taurine has to be attributed to other, yet to be defined mechanisms. Our results suggest that pharmacological doses of taurine may be particularly protective against RCIN.

Gadolinium-based contrast agents in angiography and interventional radiology

Gadolinium is useful as an alternative contrast agent for diagnostic angiographic and interventional procedures in patients with renal insufficiency or a history of a severe reaction to iodinated contrast material. Gadolinium usually is used as a "problem solver" to answer specific diagnostic questions or guide interventional procedures that cannot adequately be defined with CO2 angiography. Because of dose limitations with Gd, careful planning is required prior to its use with angiography or interventional procedures.

Gadolinium chelates in angiography and interventional radiology: a useful alternative to iodinated contrast media for angiography

Gadolinium has physical properties that are well suited for radiographic imaging. Digital subtraction angiography with a gadolinium chelate as contrast medium can provide images of suitable quality for diagnosis and intervention. The overall safety profile of gadolinium-based contrast media is excellent. In particular, these contrast media are well tolerated in patients with renal insufficiency when administered intraarterially in doses of less than 0.3-0.4 mmol per kilogram body weight, with a decreased incidence of contrast medium-induced nephropathy, as compared with similar volumes of iodinated contrast material. The currently available formulations of gadolinium chelates can be injected safely into every arterial and venous structure. However, substantial data are lacking on the intraarterial use of gadolinium in patients with renal insufficiency, particularly at doses that exceed those routinely used in magnetic resonance angiography. Gadolinium chelates in appropriate volumes are useful alternative contrast media in selected high-risk patients undergoing angiographic studies.

Prevention of contrast media-induced renal dysfunction with prostaglandin E1: a randomized, double-blind, placebo-controlled study

Preexisting renal impairment is an all-encompassing risk factor for radiocontrast-associated nephrotoxicity. Renal impairment appears to be associated with the inadequate production of renal prostaglandins at the critical time of radiocontrast administration and for a variable time period afterward. We prospectively studied 130 patients with chronic renal insufficiency (serum creatinine > or =1.5 mg/dL) who were undergoing radiocontrast administration. Using a double-blind, randomized, prospective technique, patients were assigned to either placebo or one of three prostaglandin E1 (PGE1) treatment groups (10, 20, or 40 ng/kg/min). Infusion was started 60 +/- 30 minutes before the administration of radiocontrast and was continued for a total of 6 hours. In the placebo group, radiocontrast administration resulted in a mean increase (+/- SD) in serum creatinine of 0.72 +/- 1.15 mg/dL at 48 hours. This increase was less in each of the PGE1 treatment groups after 48 hours, with a significant difference between placebo and the 20 ng/kg/min PGE1 group (P = 0.01). Using baseline adjusted means, analysis of covariance with baseline serum creatinine as the covariable demonstrated significant differences between the placebo and 20 ng/kg/min PGE1 group (P = 0.03) and between the placebo and 10 ng/kg/min PGE1 group P = 0.047). In a subgroup analysis of the diabetic patients, the increase in serum creatinine was less pronounced in the three PGE1 groups versus the placebo group, and the 20 ng/kg/min PGE1 group had the most favorable outcome. The parenteral administration of PGE1 immediately before radiocontrast exposure and continued for a period of 5 to 5.5 hours significantly reduced the elevation of serum creatinine poststudy. The most effective of the three PGE1 dosing regimens was 20 ng/kg/min.

Effect of radiologic contrast media on cell volume regulation in rabbit proximal renal tubules

RATIONALE AND OBJECTIVES

Most radiographic contrast media are hyperosmotic and able to shrink cells with which they are in contact. The authors studied cell volume control in rabbit proximal renal tubules after incubation with three contrast media: iohexol, ioxaglate, and iodixanol.

MATERIALS AND METHODS

Proximal renal tubules were isolated from rabbit kidneys. The tubules were exposed to Ringer solutions containing 5% vol/vol iohexol (final osmolality, 330 mOsm), ioxaglate (323 mOsm), iodixanol (305 mOsm), or mannitol (control solutions with identical osmolalities), and tubule volumes were monitored. After 2 hours of incubation, the tubules were stimulated with a hyposmotic Ringer solution (165 mOsm). Three groups of 10 experiments were performed.

RESULTS

All solutions induced cell shrinkage (8.3%+/-3.8 [standard error] to 15.4%+/-0.5), which was completely or partly reversible in most experiments (volume increase, 44.8%+/-14.7 to 149.9%+/-107.3) but not those with iohexol and iodixanol. With exposure to the hyposmotic solution, the cells swelled by 11.0%+/-1.8 to 39.7%+/-4.8. In general, the tubules that had been exposed to the most hyperosmotic solution swelled the most. Those exposed to contrast media showed less swelling than the mannitol-exposed controls. In all control experiments, the cells exhibited a gradual shrinkage (43.6%+/-28.5 to 87.0%+/-13). This regulatory response was partly inhibited in tubules exposed to iohexol (39.9%+/-15.8 shrinkage) or iodixanol (8.9%+/-15.8) and completely inhibited in those exposed to ioxaglate. Iohexol and ioxaglate exposure also led to a decrease in water permeability.

CONCLUSION

Exposure to hyperosmotic contrast medium tends to induce prolonged cell shrinkage, decrease the water permeability of the cellular plasma membranes, and compromise the ability to regulate cellular volume. These changes seem to reflect both the hyperosmolality of the solutions and their inherent chemical properties.

Effect of radiologic contrast material on cell volume regulation in proximal renal tubules from trout (Salmo trutta)

RATIONALE AND OBJECTIVES

Most radiographic contrast media (CM) are hyperosmotic and pose an osmotic threat to cells they are in contact with. To study these effects at the cellular level, cell volume regulatory mechanisms were observed in proximal renal tubules following exposure to the CM iohexol, ioxaglate, and iodixanol.

MATERIALS AND METHODS

Isolated renal tubules from trout (Salmo trutta) were exposed to 5% vol/vol iohexol (326 mOsm), ioxaglate (314 mOsm), or iodixanol (300 mOsm) or mannitol (to achieve the same osmolalities), and cell volume changes were observed videometrically.

RESULTS

Iohexol and ioxaglate solutions induced a rapid shrinkage (12%-13%) not followed by cell volume regulation. Without CM (same osmolality), the cells shrank 11% but then showed a 77%-88% volume recovery. This reswelling was inhibited by 55% with the Na+, K+, Cl- symporter inhibitor bumetanide (50 micromol/L). Iodixanol did not significantly affect cell volume. Tubules preincubated with CM or mannitol were then stimulated with a hypoosmotic Ringer solution (160 mOsm) resulting in a 26%-36% cellular volume increase. Compared with results of experiments without mannitol and CM, preexposure to iohexol or ioxaglate almost completely inhibited the expected regulatory shrinkage phase, while previous exposure to hyperosmotic solutions with mannitol reduced the shrinkage response by 40%-53%.

CONCLUSION

In this system, the hyperosmotic iohexol and ioxaglate cause cell shrinkage followed by an impaired cell volume regulatory response. Exposure to these two CM also inhibits cell volume regulation on hypoosmotic stimulation. The isosmotic iodixanol has no such effects. These changes appear to some extent to be a result of the CM's degree of hyperosmolality, but this property alone does not explain these findings.

Reversibility of experimental acute renal failure in rats: assessment with USPIO-enhanced MR imaging

The purpose of this study was to evaluate the potential reversibility of kidney lesions in an experimental model of acute renal failure using ultra-small particles of iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging. This study was conducted in 21 uninephrectomized rats using a model of iodinated contrast media-induced renal failure. Thirteen rats received selective intraarterial renal administration of diatrizoate (370 mg/ml) and were compared with two control groups, including six animals injected with saline and two noninjected animals. MR imaging was performed 28 hours, 8 days, and 22 days after the procedure. Each MR session included axial and coronal T1- and coronal T2-weighted images before and after intravenous administration of 60 micromol Fe/kg of USPIO. The rats were sacrificed immediately after the last MR session for pathologic evaluation. MR images were qualitatively and quantitatively interpreted with respect to pathologic data, and differences were statistically studied. At day 22, histology showed 4 severely diseased kidneys with focal areas of necrosis, 5 mildly diseased kidneys with tubular vacuolization, and 12 normal kidneys. On quantitative data, a high correlation between the percentage of negative enhancement and histologic data was observed (P < 0.05). Qualitative interpretation showed a sensitivity and specificity of USPIO-enhanced T2-weighted MR images of 88% and 91%, respectively. Follow-up enhancement curves showed a constant increase of intrarenal USPIO negative enhancement in normal kidneys between day 1 and day 22, whereas all severely involved kidneys displayed higher USPIO negative enhancement at day 1 without significant changes over time until day 22. USPIO may be useful for in vivo follow-up of the reversibility of experimentally induced iodinated contrast media renal impairment in animals.

Contrast medium-induced nephrotoxicity: pathophysiology and prevention

Contrast medium-induced nephrotoxicity (CMN) is a common form of iatrogenic acute renal failure. Typically, patients experience changes in serum creatinine or creatinine clearance between 1 and 5 days after exposure to a contrast medium, but they rarely require dialysis. The mechanism for CMN is not understood, but renal insufficiency, dehydration, and congestive heart failure are risk factors. The frequency of CMN with high-osmolality versus low-osmolality media is controversial. Prophylaxis can reduce CMN. Of many different strategies, hydration with normal saline before and after exposure offers the best protection with the fewest adverse effects.

Prostaglandin E1: a new agent for the prevention of renal dysfunction in high risk patients caused by radiocontrast media? PGE1 Study Group

BACKGROUND

Acute renal failure following the administration of radiocontrast media (RCM) is a complication found especially in patients with impaired renal function. Within the limits of a pilot study, the objective was to (a) show the effectiveness and compatibility of prostaglandin E(1) (PGE(1)=Alprostadil) in preventing acute renal failure in patients with elevated levels of serum creatinine and (b) to identify the most appropriate PGE(1)-dose.

METHODS

130 patients with renal impairment (serum creatinine >/=1.5 mg/dl) were included in the study prior to intravascular RCM injection. The patients received one of three different doses of PGE(1) (10, 20, or 40 ng/kg bodyweight/min) or placebo (physiologic sodium chloride solution) intravenously over a time period of 6 h (beginning 1 h prior to RCM application). Serum creatinine was measured 12, 24, and 48 h post RCM-application and creatinine clearance was determined with two 12 h collection periods, as well as one 24 h collection within 48 h post RCM administration. Adverse events during PGE(1) administration were recorded.

RESULTS

In the placebo group, the mean elevation of serum creatinine was markedly higher (0.72 mg/dl) 48 h after RCM administration compared with the three PGE(1) groups (0.3 mg/dl in the 10 ng/kg/min group, 0. 12 mg in the 20 ng/kg/min group, and 0.29 mg/dl in the 40 ng/kg/min group). No clinically relevant changes were seen regarding the creatinine clearance in the four groups examined.

CONCLUSIONS

Results from this pilot-study suggest that intravenous PGE(1) may be used efficaciously and safely to prevent RCM-induced renal dysfunction in patients with pre-existing impaired renal function.

Biology of renal aging in humans

Advancing age is usually accompanied by a decline in glomerular filtration rate and an increased incidence of certain renal and electrolyte disorders. These include an increased susceptibility to acute renal failure, hypo- and hypernatremia, hyperkalemia, and hypertension. This report discusses anatomic and physiological observations related to the aged human kidney and explores the various theories and postulated mechanisms underlying these changes.

Lower extremity arteriography with use of iodinated contrast material or gadodiamide to supplement CO2 angiography in patients with renal insufficiency

PURPOSE

To determine if the use of nonionic contrast material, as compared to the use of gadodiamide to supplement carbon dioxide angiography in patients with peripheral vascular disease (PVD) and chronic renal insufficiency (CRI), results in significant worsening of renal function.

MATERIALS AND METHODS

Lower extremity angiographic procedures (diagnostic and diagnostic/intervention) were performed in 40 patients with CRI (baseline serum creatinine [Cr] > 1.5 mg/dL) using CO2 alone or CO2 supplemented with the use of either nonionic contrast material or gadodiamide (up to 0.4 mmol/kg). Serum creatinine levels were obtained before the procedure and at 48 hours after the procedure. The peak Cr level was also determined for patients with a significant (> 0.5 mg/dL) Cr elevation.

RESULTS

Forty-two lower extremity angiographic procedures (19 diagnostic and 23 diagnostic/interventions) were performed in 40 consecutive patients from August 1997 to October 1998, with a mean preprocedure Cr of 2.2 mg/dL and a mean postprocedure Cr of 2.4 mg/dL. Twenty-five of the 40 patients (63%) had diabetes mellitus. Fifteen procedures, including six interventions, were performed utilizing CO2 and nonionic contrast material in 15 patients. Six of these 15 patients (40%) demonstrated a Cr increase > 0.5 mg/dL at 48 hours. Seven procedures, including two interventions, were performed with CO2 alone in seven patients. No patients in this group demonstrated an increase in serum creatinine of greater than 0.5 mg/dL at 48 hours. Twenty procedures, including 15 interventions, were performed with CO2 and gadodiamide in 18 patients. In one of these 20 procedures (5%) there was an increase in Cr > 0.5 mg/dL at 48 hours The difference in worsening renal function for the nonionic contrast group (six of 15) compared with the CO2/gadodiamide group (one of 20) was statistically significant (P = .03). When comparing the use of CO2 and nonionic contrast material versus CO2 alone and with gadodiamide (six of 15 versus one of 27), the difference is also statistically significant (P < .01). The average volume of supplemental contrast material was similar in the nonionic contrast material and gadodiamide groups, as was the average volume of supplemental nonionic contrast material in the six patients with an increased Cr.

CONCLUSION

The use of small volumes of nonionic contrast material to supplement CO2 angiography in patients with PVD and CRI can be associated with a significant increased risk of worsening renal function when compared to angiography performed with CO2 alone or CO2 and gadodiamide.

The renal effect of low-dose dopamine in high-risk patients undergoing coronary angiography

OBJECTIVES

The purpose of the study was to examine the potential renal protective effect of low-dose dopamine in high-risk patients undergoing coronary angiography.

BACKGROUND

Contrast nephropathy is prevalent in patients with chronic renal failure (CRF) and/or diabetes mellitus (DM). Decreased renal blood flow due to vasoconstriction was suggested as a contributory mechanism. Low-dose dopamine has a dilatory effect on the renal vasculature.

METHODS

Sixty-six patients with mild or moderate CRF and/or DM undergoing coronary angiography were prospectively double-blindedly randomized, to either 120 ml/day of 0.9% saline plus dopamine 2 microg/kg/min (Dopamine group) or saline alone (Control group) for 48 h.

RESULTS

Thirty-three Dopamine-treated (30 diabetics and 6 with CRF) and 33 Control (28 diabetics and 5 with CRF) patients were compared. Plasma creatinine (Cr) level increased in the Control group from 100.6+/-5.2 before to 112.3+/-8.0 micromol/liter within five days after angiography (p = 0.003), and in the Dopamine group from 100.3+/-5.4 before to 117.5+/-8.8 micromol/liter after angiography (p = 0.0001), respectively. There was no significant difference in the change of Cr level (deltaCr) between the two groups. However, in a subgroup of patients with peripheral vascular disease (PVD), deltaCr was -2.4+/-2.3 in the Control group and 30.0+/-12.0 micromol/liter in the Dopamine group (p = 0.01). No significant difference occurred in deltaCr between Control and Dopamine in subgroups of patients with preangiographic CRF or DM.

CONCLUSIONS

Contrast material caused a small but significant increase in Cr blood level in high-risk patients. There is no advantage of dopamine over adequate hydration in patients with mild to moderate renal failure or DM undergoing coronary angiography. Dopamine should be avoided in patients with PVD exposed to contrast medium.

Pathophysiology of radiocontrast nephropathy: a role for medullary hypoxia

Recent experimental data underlies the role of hypoxic tubular injury in the pathophysiology of radiocontrast nephropathy. Although systemic transient hypoxemia, increased blood viscosity, and a leftward shift of the oxygen-hemoglobin dissociation curve may all contribute to intrarenal hypoxia, imbalance between oxygen demand and supply plays a major role in radiocontrast-induced outer medullary hypoxic damage. Low oxygen tension normally exists in this renal region, reflecting the precarious regional oxygen supply and a high local metabolic rate and oxygen requirement, resulting from active salt reabsorption by medullary thick ascending limbs of Henle's loop. Radiologic contrast agents markedly aggravate outer medullary physiologic hypoxia. This results from enhanced metabolic activity and oxygen consumption (as a result of osmotic diuresis and increased salt delivery to the distal nephron) because the regional blood flow and the oxygen supply actually increase. The latter effect may result in part from the activation of various regulatory mediators of outer medullary blood flow to ensure maximal regional oxygen supply. Low-osmolar radiocontrast agents may be less nephrotoxic because of the smaller osmotic load and vasomotor alterations. Experimental radiocontrast-induced renal failure requires preconditioning of animals with various insults (for example, congestive heart failure, reduced renal mass, salt depletion, or inhibition of nitric oxide and prostaglandin synthesis). In all these perturbations, which resemble clinical conditions that predispose to contrast nephropathy, outer medullary hypoxic injury results from insufficiency or inactivation of mechanisms designed to preserve regional oxygen balance. This underlines the importance of identifying and ameliorating predisposing factors in the prevention of this iatrogenic disease.

Arteriography in chronic renal failure: a case for carbon dioxide

PURPOSE

The aim of this study was to assess the utilisation of carbon dioxide arteriography, performed with a simple injection system, as the imaging technique of choice in patients with chronic renal failure.

METHODS

Patients with chronic renal impairment who required arterial imaging or intervention were recruited for carbon dioxide angiography. Demographic data were prospectively recorded and pre- and post-arteriogram renal function was quantified. Radiographic images were graded by an independent radiologist.

RESULTS

Twenty-eight patients underwent renal or aorto-femoral studies with only one failure. There were no cases of contrast-induced nephropathy. Twenty-two of the films (79%) were graded as excellent or good, four as acceptable and two were considered to be poor (non-diagnostic).

CONCLUSIONS

This study has demonstrated that carbon dioxide angiography is a safe and clinically effective procedure in patients with chronic renal failure.

Comparative toxic effects of iobitridol and iohexol on the kidney

RATIONALE AND OBJECTIVES

The authors compare the toxic effects of iobitridol and iohexol, which are nonionic contrast media with equivalent osmolalities and viscosities on the kidney.

METHODS

In a rat acute renal failure (ARF) model, iobitridol or iohexol (both at the dose of 2.87 g I/kg) were injected to rats after pretreatment with indomethacin and N omega-nitro-L-arginin methyl ester. The effects on histopathology, creatinine clearance, and urinary N-acethyl-beta-D-glucosaminidase (NAG) activity were assessed. In a rat renal slice system, the slices were exposed to iobitridol or iohexol (both at the concentration range of 17.5-70 mg iodine/mL) for 60 min. The accumulation of para-aminohippuric acid (PAH), an organic anion, and the intracellular potassium content as the indicators of renal tubular injury were measured to assess the direct effects of iobitridol and iohexol on renal tubules.

RESULTS

In the ARF model, no significant difference was detected between the effects of iobitridol and those of iohexol on the creatinine clearance and urinary NAG activity 24 hours after the injection. However, iobitridol produced a lower degree and incidence of renal tubular injury of renal proximal tubules (P < 0.001) and distal tubules (P < 0.05) compared with iohexol. In the rat renal slice system, the iobitridol treatment had significantly less effect on the PAH accumulation compared with iohexol (P < 0.001). There were no changes in the intracellular potassium content.

CONCLUSIONS

These findings suggest that iobitridol has significantly less toxic effects on the kidney compared with iohexol under the condition of our experiment.

Contrast media-induced nephrotoxicity--questions and answers

The intravascular administration of contrast media (CM) can produce acute haemodynamic changes in the kidney characterized by an increase in renal vascular resistance and a decrease in the glomerular filtration rate (GFR). These changes may lead to clinically significant reduction in renal function in patients with pre-existing risk factors such as diabetic nephropathy, congestive heart failure and dehydration. The pathophysiology of the renal haemodynamic effects of CM involves activation of the tubuloglomerular feedback (TGF) mechanism and the modulation of the intrarenal production of vasoactive mediators such as prostaglandins, nitric oxide, endothelin and adenosine. The TGF response is osmolality-dependent and accounts for about 50% of the acute functional effects of high osmolar CM on the kidney. Reduction in the synthesis of the endogenous vasodilators nitric oxide and prostaglandins increases the nephrotoxicity of CM. Endothelin and adenosine play a crucial role in mediating the acute functional effects of CM. Antagonists of these mediators attenuate the reduction in renal function induced by contrast agents. Vacuolization of the cells of the proximal tubules and necrosis of those of the medullary ascending limbs of loops of Henle are the main structural effects of CM in the kidney. The reduction in renal function induced by CM could be minimized by the use of low osmolar CM and adequate hydration. The prophylactic administration of calcium channel blockers and adenosine antagonists such as theophylline may also offer some protective effect.

Comparative cytotoxicity of low- and high-osmolar contrast media to human fibroblasts and rat mesangial cells in culture

RATIONALE AND OBJECTIVES

The authors investigate the relative sensitivity of rat mesangial cells to iodinated contrast media (CM) and control solutions versus less differentiated cells (ie, human fibroblasts) and compare the effects of low-osmolar ionic (ioxaglate) and nonionic (iopamidol) and high-osmolar ionic (diatrizoate) CM on rat mesangial cells.

METHODS

The cytotoxic effects of ioxaglate and control solutions of sodium chloride and mannitol were assessed by neutral red uptake in isolated rat mesangial cells and human fibroblasts. In a second series of studies, the cytotoxic effects of ioxaglate, iopamidol, and diatrizoate (0 to 100 mg I/mL) on rat mesangial cells were compared.

RESULTS

Rat mesangial cells were more sensitive to the cytotoxic effects of ioxaglate than the less differentiated human fibroblasts between 70 and 100 mg I/mL. A similar discrepancy was observed in the case of control solutions, sodium chloride, and mannitol. Ioxaglate and iopamidol induced a similar level of cytotoxicity in rat mesangial cells whereas the high-osmolar agent diatrizoate was significantly more cytotoxic. However, the calculated inhibitory concentrations of 50% of all three CM were associated with similar osmolalities, suggesting a major role for this parameter in the case of such media.

CONCLUSIONS

Rat mesangial cells are more sensitive to the cytotoxic effects of CM and hyperosmolar solutions than the less differentiated human fibroblasts. High-osmolar CM are more cytotoxic than ionic and nonionic low-osmolar CM to rat mesangial cells. Ionicity seems to play no deleterious role at similar iodine concentrations because ioxaglate and iopamidol had equivalent cytotoxic effects on mesangial cells.

Endothelin and atrial natriuretic peptide levels following radiocontrast exposure in humans

Radiocontrast exposure is associated with vasoconstriction of the renal vascular bed and, in certain circumstances, with acute renal failure. This may be influenced by the volume of contrast infused or underlying disease, such as diabetes or renal failure. Changes in circulating vascular regulators, such as endothelin and atrial natriuretic peptide (ANP), may play a role in the development and/or prevention of acute renal failure. Nineteen patients undergoing arteriographic procedures were divided into two groups: large-volume contrast (> or = 150 mL; n = 7) and small-volume contrast (< 150 mL; n = 12). Circulating endothelin levels increased significantly (from 12.3 +/- 1.1 pmol/L to 19.4 +/- 2.2 pmol/L; P < 0.05) following large-volume contrast exposure (group 1) but not following small-volume contrast exposure (group 2) (13.9 +/- 1.7 pmol/L to 12.2 +/- 0.09 pmol/L). ANP levels increased significantly in both groups: 43 +/- 15 pg/mL to 75 +/- 21 pg/mL in group 1 and 33 +/- 16 to 106 +/- 39 pg/mL in group 2. Data from an additional eight patients with underlying diabetes mellitus and/or renal insufficiency also were obtained and were considered separately. Endothelin levels were higher at baseline and increased significantly after contrast (25.7 +/- 5 pmol/L to 55.4 +/- 18 pmol/L) despite the relatively small average volume of contrast infused (112 +/- 15 mL). ANP levels were also highest in these patients (211 +/- 43 pg/mL precontrast and 323 +/- 65 pg/mL postcontrast). No group had a significant change in serum creatinine following contrast exposure. In conclusion, large-volume radiocontrast exposure is associated with an increase in both circulating endothelin and ANP levels. Patients with underlying diabetes or renal insufficiency may have higher baseline levels and a greater tendency to increase endothelin after contrast exposure. While an increase in endothelin may contribute to renal vasoconstriction following radiocontrast exposure, simultaneous increases in ANP may serve to offset this response and protect against changes in renal function.

Nephrotoxicity of low-osmolality contrast media

To evaluate renal function after the use of a low-osmolality radiological contrast medium (CM), we prospectively analyzed 39 patients submitted to the following examinations: arteriography (n = 32), phlebography (n = 3), computed tomography (n = 3), angioplasty (n = 1), and retrograde pyelography (n = 1). The patients were divided into three groups: group 1, control, formed by renal donors (CT, n = 11 and 11 exams); group 2, hypertensive patients (HYPT, n = 15 and 16 exams); and group 3, patients with diseases of multiple etiologies (MIX, n = 13 patients and 13 exams). Additionally, the patients were divided according to their renal function into: group 4, with a moderate deficit of renal function, creatinine clearance (CrCl) 25 to 60 mL/min (n = 15 patients and 15 exams); and group 5, with a mild deficit of renal function, CrCl > or = 60 mL/min (n = 14 patients and 14 exams). The CM utilized was ioxaglic acid (Hexabrix) the incidence of acute renal failure (ARF) among the patients studied was 12.5% (5/40), and CrCl was the best parameter to monitor the alterations in renal function, which occurred in 35% of the patients, although the changes were mild, reversible, and did not need any therapeutic interventions. The triggering of ARF in these patients may have been due to multiple factors presented at time of CM examination. Thus, it is not possible to identify a single risk factor. However, it is probable that previous important impairment of renal function was the most expressive risk factor.

Utility of the creatinine prior to intravenous contrast studies in the emergency department

The purpose of this study was to determine if it is possible to identify patients who have underlying renal insufficiency by evaluating their risk factors prior to receiving intravenous contrast in the emergency department (ED). This would allow selective ordering of a creatinine, resulting in a cost and time savings. This prospective study involved 640 consecutive adult patients presenting to the ED with a clinical indication for an intravenous contrast study. Physicians completed a study form evaluating a patient's risk factors for renal insufficiency. A serum creatinine was then obtained on all patients with a level of 1.6 mg/dl or greater considered abnormal. Thirty-five (5.5%) had an abnormal creatinine. Of these 35 patients, 27 (4.2%) had identifiable risk factors for renal insufficiency. Eight (1.3%) had no identifiable risk factors for renal insufficiency. In conclusion, it is possible to identify approximately 99% of ED patients at risk for contrast induced nephropathy by evaluation of risk factors.

Protection from the nephrotoxicity of contrast dye

Previous studies have reported a 4%-50% incidence of acute renal failure (ARF) following the use of radiocontrast media in patients with preexisting chronic renal insufficiency. In these studies, ARF was defined as a rise of the serum creatinine of at least 1 mg/dl above baseline. Using the same criteria, we studied 214 patients undergoing various intravascular radiocontrast media procedures. Patients were infused with a specially prepared cocktail solution (NSMF) containing 1000 ml half-normal saline, 12.5 g of mannitol (M), I ampule NaHCO3, and 200 mg of furosemide (F) at 100 ml/h from one hour prior to two hours after the procedure. Urinary output was replaced with normal saline for at least 6 h after the procedure. Seven percent of the patients developed acute renal insufficiency. Only 3% of the patients had a rise in serum creatinine greater than 2 mg/dl. No patient required dialysis therapy after the procedure. There was one unrelated death caused by acute myocardial infarction postangioplasty. Risk factors for development of ARF despite cocktail administration included the presence of diabetes mellitus and angiotensin converting enzyme (ACE) inhibitor therapy. We concluded that the properly administered NSMF solution protects against radiocontrast dye induced renal failure. In select patients with chronic renal insufficiency, consideration should be given to withholding ACE inhibitor therapy for 24-48 h prior to administration of intravenous radiocontrast dye. A large controlled trial will be required to establish whether the NSMF solution offers benefit beyond that of saline hydration alone.

Iodinated contrast media-induced nephropathy: pathophysiology, clinical aspects and prevention

Administration of iodinated contrast media (CM) for radiographic purposes is a preoccupying cause of acute renal failure. This review of the literature deals with what is known about physiopathology, clinical course, risk factors and prevention. Factors involved in the pathophysiology of CM-induced acute renal failure are vasoconstriction, direct tubular cell injury and tubular obstruction by casts. In the case of pre-existing renal hypoperfusion, CM may disturb the complex interaction between factors which modulate renal haemodynamics by increasing vasoconstrictor factors, notably endothelin peptides. The renal medulla, a zone characterized by a high metabolic activity and a low oxygen tension, may be a specific target for CM-induced effects. CM-induced nephropathy (CMN) is essentially observed in patients with one or more associated risk factors (chronic renal failure, dehydration, diabetes mellitus with impaired renal function, multiple myeloma, large CM volume, intra-arterial rather than intravenous route, etc). There is much debate as to whether newer low osmolar CM (LOCM) are better tolerated than conventional high osmolar CM (HOCM). Most of the animal studies clearly demonstrate the advantages of LOCM over HOCM. Clinical literature is far more confusing, although some recent studies and one meta-analysis demonstrate that LOCM are better tolerated in patients with impaired renal function. The low number of comparative clinical trials carried out in high risk patients, wide variability in CMN definitions, limited number of patients enrolled and inadequacy of various selected endpoints may explain difficulties experienced in demonstrating this advantage. Furthermore, while hydration is correctly maintained during clinical trials, this is not always true in clinical practice. Such a discrepancy could lead to underestimation of the potential advantage of LOCM over HOCM. Effective prevention should associate the correct hydration of patients, identification and, when possible, optimal correction of risk factors, avoidance of repeated CM injections within a short period of time and temporary disruption of treatment with other nephrotoxic drugs (non steroidal antiinflammatory drugs, aminoglycosides, etc).

The functional effects of gadolinium-DTPA on the isolated perfused rat kidney

Clinical experience suggests that Gd-DTPA has no deleterious effect on renal function. We have evaluated the effects of a large dose (0.6 ml/kg body weight) of this contrast agent on the function of the isolated perfused rat kidney. Gd-DTPA led to a mild, transient increase in glomerular filtration rate with no subsequent fall during the 30 minute observation period. However, Gd-DTPA induced an increase in renal vascular resistance (+ 10%, P < 0.05) as a mild decrease in renal perfusate flow was observed during the experimental phase when compared to that of control kidneys. No significant effect was demonstrated on the fractional excretion of albumin or the fractional reabsorption of sodium. These data support, in an ex vivo experimental model, the clinical experience of the safety of this paramagnetic contrast agent in relation to renal function.