Nephrotoxicity of ionic and non-ionic contrast material in digital vascular imaging and selective renal arteriography

Intravenous Injection of Ioxilan, Iohexol and Diatrizoate

Effects of intravenous ioxilan, a new third generation non-ionic contrast medium, diatrizoate, iohexol and saline on urine profiles were compared. Albumin, glucose, sodium, phosphate, and the enzymes NAG, LDH and GGT were followed in 24 normal rats over 7 days. Diatrizoate significantly affected all profile components during the first two hours. Albuminuria was significantly greater after diatrizoate than after iohexol or ioxilan, and excretion of glucose, LDH and GGT was significantly higher than after ioxilan. Both iohexol and ioxilan increased the excretion of albumin, LDH and GGT, while iohexol also significantly increased excretion of glucose and sodium. There was a greater excretion of glucose and GGT after iohexol than after ioxilan. Saline did not induce any changes. At day 7, serum sodium, urea, creatinine, and albumin were normal for all test substances, and kidney histology revealed no difference between the groups of animals. It is thus concluded that both high osmolar ionic and low osmolar non-ionic contrast media may cause temporary glomerular and tubular dysfunction in rats. In this model, the kidney is affected most by diatrizoate, less by iohexol, and least by ioxilan.

Renal Effects of the Non-Ionic Contrast Medium Iopentol after Intravenous Injection in Healthy Volunteers

Renal effects of the new non-ionic contrast medium iopentol in increasing doses were assessed and compared with the effects of physiologic saline. Twenty-four healthy male volunteers, allocated to three dose groups, were given iopentol intravenously in doses of 0.3, 0.6, and 1.2 g I/kg body weight, respectively. The highest dose group was also given physiologic saline separately as a control. The diuresis increased in all groups, most in the highest dose group, and with a concomitant fall of urine osmolality and increase in osmolar clearance. A slight decrease of serum osmolality, creatinine and urea occurred at 3 hours due to hemodilution. The glomerular filtration rate was unaffected by iopentol. The urinary excretion of albumin and β2-microglobulin was unchanged. However, urinary N-acetyl-β-glucosaminidase and alkaline phosphatase increased significantly, most in the highest dose group. All changes were reversible.

Renal Effects of Iopentol and Iohexol after Intravenous Injection

Renal effects of the 2 non-ionic contrast media iopentol and iohexol were investigated and compared in a double-blind, randomized parallel study where 30 patients received iopentol, and 31 patients iohexol intravenously for abdominal CT. The dosage of contrast medium (350 mg I/ml) was 700 mg I/kg body weight. Only one patient (in the iohexol group) had an increase in serum creatinine of more than 50%. Iopentol and iohexol had no effects on the mean serum values of creatinine, urea, and β2-microglobulin (β2-MG) nor on creatinine clearance. The urinary excretion of albumin and β2-MG was also unchanged. The excretion of the proximal tubular enzymes alkaline phosphatase and N-acetyl-β-glucosaminidase was increased. No significant difference between iopentol and iohexol was found.

The Choice of the Iodinated Radiographic Contrast Media to Prevent Contrast-Induced Nephropathy

In patients with preexisting renal impairment, particularly those who are diabetic, the iodinated radiographic contrast media may cause contrast-induced nephropathy (CIN) or contrast-induced acute kidney injury (CI-AKI), that is, an acute renal failure (ARF), usually nonoliguric and asymptomatic, occurring 24 to 72 hours after their intravascular injection in the absence of an alternative aetiology. Radiographic contrast media have different osmolalities and viscosities. They have also a different nephrotoxicity. In order to prevent CIN, the least nephrotoxic contrast media should be chosen, at the lowest dosage possible. Other prevention measures should include discontinuation of potentially nephrotoxic drugs, adequate hydration with i.v. infusion of either normal saline or bicarbonate solution, and eventually use of antioxidants, such as N-acetylcysteine, and statins.

Acute kidney injury by radiographic contrast media: pathogenesis and prevention

It is well known that iodinated radiographic contrast media may cause kidney dysfunction, particularly in patients with preexisting renal impairment associated with diabetes. This dysfunction, when severe, will cause acute renal failure (ARF). We may define contrast-induced Acute Kidney Injury (AKI) as ARF occurring within 24-72 hrs after the intravascular injection of iodinated radiographic contrast media that cannot be attributed to other causes. The mechanisms underlying contrast media nephrotoxicity have not been fully elucidated and may be due to several factors, including renal ischaemia, particularly in the renal medulla, the formation of reactive oxygen species (ROS), reduction of nitric oxide (NO) production, and tubular epithelial and vascular endothelial injury. However, contrast-induced AKI can be prevented, but in order to do so, we need to know the risk factors. We have reviewed the risk factors for contrast-induced AKI and measures for its prevention, providing a long list of references enabling readers to deeply evaluate them both.

Side effects of radiographic contrast media: pathogenesis, risk factors, and prevention

Radiocontrast media (RCM) are medical drugs used to improve the visibility of internal organs and structures in X-ray based imaging techniques. They may have side effects ranging from itching to a life-threatening emergency, known as contrast-induced nephropathy (CIN). We define CIN as acute renal failure occurring within 24-72 hrs of exposure to RCM that cannot be attributed to other causes. It usually occurs in patients with preexisting renal impairment and diabetes. The mechanisms underlying CIN include reduction in medullary blood flow leading to hypoxia and direct tubule cell damage and the formation of reactive oxygen species. Identification of patients at high risk for CIN is important. We have reviewed the risk factors and procedures for prevention, providing a long list of references enabling readers a deep evaluation of them both. The first rule to follow in patients at risk of CIN undergoing radiographic procedure is monitoring renal function by measuring serum creatinine and calculating the eGFR before and once daily for 5 days after the procedure. It is advised to discontinue potentially nephrotoxic medications, to choose radiocontrast media at lowest dosage, and to encourage oral or intravenous hydration. In high-risk patients N-acetylcysteine may also be given.

Evaluation of microalbuminuria after non-ionic radiocontrast medium exposure in patients undergoing coronary angiography

Transient and massive glomerular proteinuria, previously reported as one of the nephrotoxic reactions after ionic radiocontrast medium (RCM) exposure, is rarely observed in patients since the introduction of non-ionic RCM. However, whether the very low-range microalbuminuria might be encountered after non-ionic RCM exposure remains unknown. In this study we sought to investigate the effects of non-ionic RCM (Ultravist 370) exposure on the presence of microalbuminuria, defined as urine albumin-to-creatinine ratio (UACR) >30 mg/g, by a turbidmetric method in total of 64 patients (17 female, mean age 58+/-12 years) undergoing coronary angiography. The results showed that after non-ionic RCM (mean volume 103+/-57 ml) exposure, no significant differences were found in urinary albumin concentration or UACR; however, urinary creatinine was significantly reduced from 116+/-62 to 69+/-43 mg/dl (p<0.001). Changes in the presence of microalbuminuria before and after procedure were also not significant (p=0.891, McNemar test). In conclusion, non-ionic RCM exposure during CAG had negligible effect on the excretion of urinary albumin even within the detection range of microalbuminuria.

Contrast medium use

Various properties of iodinated contrast media (osmolality, ionic versus nonionic, and viscosity) may contribute to contrast-induced nephropathy (CIN). Therefore, the choice of contrast medium affects the risk for CIN. There is good evidence that low-osmolar contrast media are less nephrotoxic than high-osmolar contrast media in patients at increased risk for CIN who receive intra-arterial iodinated contrast. Current evidence suggests that nonionic isosmolar contrast presents the lowest risk for CIN in patients with chronic kidney disease (CKD), particularly in those patients with diabetes mellitus. Intra-arterial administration of contrast media may be associated with a greater risk for CIN above that observed with intravenous administration. The use of gadolinium or CO(2) as alternative contrast media to avoid the risk of nephrotoxicity cannot be substantiated by clinical trials and therefore cannot be recommended. Most studies show that, within a class, higher volumes (>100 mL) of iodinated contrast medium are associated with a higher risk for CIN. However, in patients at high risk, such as those with CKD and diabetes, even small volumes of contrast medium can have adverse effects on renal function.

Drug-induced acute kidney injury

PURPOSE OF REVIEW

The purpose of this review is to describe the most prevalent mechanisms of drug-induced acute kidney injury, to define the risk factors for nephrotoxicity, and to analyze the available evidence for preventive measures.

RECENT FINDINGS

Drug toxicity remains an important cause of acute kidney injury that, in many circumstances, can be prevented or at least minimized by vigilance and early intervention. Recent studies have resulted in increased insight into the subcellular mechanisms of drug nephrotoxicity. Further improvement is to be expected from the identification of early markers of nephrotoxicity and an increasing involvement of a clinical pharmacist.

SUMMARY

The main mechanisms of nephrotoxicity are vasoconstriction, altered intraglomerular hemodynamics, tubular cell toxicity, interstitial nephritis, crystal deposition, thrombotic microangiopathy, and osmotic nephrosis. Before prescribing a potentially nephrotoxic drug, the risk-to-benefit ratio and the availability of alternative drugs should be considered. Modifiable risk factors should be corrected. The correct drug dosage should be prescribed. Patients should be pre-hydrated and the glomerular filtration rate should be frequently monitored during the administration of a potentially nephrotoxic drug. Studies are needed to further elucidate the mechanisms of nephrotoxicity to design more-rational prevention and treatment strategies. Computer-based prescriber-order entry and an appropriately trained intensive care unit pharmacist are particularly helpful to minimize medication errors and adverse drug events.

Comparison of contrast enhanced MR-angiography-MRI and digital subtraction angiography in the evaluation of pancreas and/or kidney transplantation patients: initial experience

To evaluate whether combined contrast enhanced MRA and MRI (ce-MRA-MRI) has the potential to replace intra-arterial DSA (i.a.DSA) in patients with impaired graft function or suspected of vascular complications after pancreas and/or kidney transplantation. 7 patients after combined pancreas-kidney and 22 patients after kidney transplantation underwent ce-MRA-MRI and i.a.DSA within a 3 days interval. Qualitative and quantitative comparison of the arterial and venous supply, the parenchyma and urinary collecting system was made. Both ce-MRA and i.a.DSA showed good results in the detection of arterial stenoses. However, ce-MRA falsely suggested stenoses if vascular clips were used; on the other hand, i.a.DSA was less informative if the graft arteries were very tortuous. Ce-MRA was superior in depicting the venous anatomy (p < 0.001) and the parenchymal enhancement of the pancreatic grafts. For the assessment of the contrast excretion, the pyelocalyceal system and the ureter of the renal graft ce-MRA-MRI was superior (p < 0.001), for small caliber arteries in the renal grafts i.a.DSA was of greater value (p < 0.001). The combination of ce-MRA and MRI is reliable for evaluating the vascular anatomy and has several advantages over i.a.DSA after pancreas and/or kidney transplantation. It can replace i.a.DSA in patients with impaired graft function or suspected of vascular complications after pancreas and/or kidney transplantation.

Renal effects of cardiac angiography with different low-osmolar contrast media

The aim of this study was to evaluate the renal effects of cardiac angiography performed with three low-osmolar contrast media (CM): iopromide (IPR), ioversol (IVR) and ioxaglate (IOX). IPR and IVR are non-ionic CM, IOX is an ionic CM. Different parameters of renal function were determined before and 6, 24, 48, 72 hrs after angiography in 45 patients: 15 patients were examined with IPR, 15 with IVR and 15 with IOX. Glomerular effects--Plasma creatinine increased slightly at the 24th hour after IVR and IOX and at 48 hours after IOP. A significant increase in plasma beta2-microglobulin was observed, at the same time, only after IOX. A significant decrease in creatinine clearance was found at 6 hours after IOX. No significant variations in glomerular filtration rate (GFR) and in effective renal plasma flow were found at 48 hours after cardiac angiography; while filtration fraction was significantly reduced after IOP and IOX. Tubular effects--A marked decrease in sodium clearance and a relevant increase of urinary activities of different tubular enzymes were found after cardiac angiography with all CM, but were more evident after the ionic CM IOX, than after the two non-ionic agents. These tubular effects reached the maximum between 6 and 24 hours and returned to baseline within 72 hrs after cardiac angiography. In conclusion, slight glomerular effects were observed mainly after IOX. A reversible tubular malfunction was found with the three low-osmolar CM and was more evident after ionic CM IOX. thus suggesting that other mechanisms, besides osmolarity, play a role in tubular toxicity due to CM. In no patient did the glomerular and tubular effects of CM have a clinical relevance.

Carbon dioxide digital subtraction angiography for renal artery stent placement

PURPOSE

To determine the efficacy of renal artery stent placement with use of carbon dioxide as the primary contrast agent.

MATERIALS AND METHODS

Seventeen hypertensive patients with renal ostial stenosis were evaluated and underwent stent placement with use of CO2 digital subtraction angiography (DSA). Besides hypertension, 11 patients had decreased renal function, three had iodinated contrast material allergy, one patient had both, and two had neither. Supplemental iodinated contrast material (25 mL or less) was used in five patients. Preprocedure and postprocedure serum creatinine levels were obtained to evaluate the effect of CO2 on renal function. Arteriography was used to evaluate stent positioning.

RESULTS

Twenty-three Palmaz stents were placed in 17 patients. Six placements were bilateral, with a total of nine right and 14 left. No additional stents were required to correct malposition. One patient had a mildly significant, yet transient, rise in the postprocedure creatinine level. This patient received 10 mL of iodinated contrast material in addition to CO2. There were no allergic reactions.

CONCLUSION

The utilization of CO2 DSA facilitates the accurate placement of renal artery stents by eliminating the concern for contrast material-associated nephropathy and allergy. These attributes, coupled with the benefit of low viscosity, permit unrestricted imaging, guidance, and precise positioning not afforded by iodinated contrast material.

Comparison of Iotrolan 320 and Iohexol 350 in cardiac angiography: a randomised double-blind clinical study

OBJECTIVE

A double-blind randomised study was conducted in two British centres, to evaluate the safety, tolerance and efficacy of the new dimeric non-ionic contrast medium Iotrolan 320 in comparison with the monomeric non-ionic compound Iohexol 350 in coronary angiography.

METHODS AND MATERIAL

120 patients were randomised to receive either Iotrolan at a concentration of 320 mgI/ml or Iohexol at a concentration of 350 mgI/ml, during selective coronary angiography and left ventriculography. The variables measured were: maximum increase of the left ventricular end-diastolic pressure up to 6 min after ventriculography, haemodynamic and electrocardiographic variables, arrhythmogenicity, clinical laboratory parameters, tolerance, adverse events and efficacy.

RESULTS

Iotrolan resulted in a smaller change of left ventricular end-diastolic pressure compared to Iohexol, but the difference was not statistically significant. Transient changes in left ventricular systolic pressure, intra-arterial systolic pressure, intra-arterial diastolic pressure, and in electrocardiographic parameters, occurred after the injections, but they were not clinically significant. Changes in the clinical laboratory markers from baseline values were comparable between the two groups and confirmed good renal and hepatic tolerance. During the left ventriculogram, Iotrolan resulted in less symptoms compared to Iohexol (P = 0.002). Adverse events, which were mild or moderate in most cases, were observed with no statistical difference between the two agents. The contrast quality of both agents was good with no statistical difference.

CONCLUSION

This study did not show a significant difference between Iotrolan 320 and Iohexol 350 with regard to cardiovascular safety or patient tolerance, except for a minor difference in the intensity of heat/warmth sensation.

The effect of triathlon on urinary excretion of enzymes and proteins

In order to investigate the effect of triathlon and renal function of normal subjects, we evaluated the excretion of urinary enzymes and proteins before and after triathlon. From 6 subjects samples were obtained 24 hours after the first urine collection. We performed quantification of urinary total protein, beta2-microglobulin (beta2-M), N-acetyl-beta-D-glucosaminidase activity (NAG), and concentration of urinary creatinine from each participant. There was a significant increase in urinary total protein excretion immediately after triathlon (p<0.01). The urinary beta2-M and NAG excretions after triathlon were higher than the initial values. Post-exercise proteinuria in one subject persisted until the next morning, whereas the increased excretion of urinary beta2-M and NAG returned to the pre-exercise level at least 24 hours after triathlon. It appears to be reasonable to presume that glomerular damage may persist in some subjects who do heavy exercise.

Tubular toxicity is the main renal effect of contrast media

The aim of this study is to evaluate the effects of contrast media on both tubular and glomerular function. Different parameters of tubular and glomerular function were determined before and at 1, 3, and 5 days after the intravascular administration of contrast media in 100 adult renal patients (plasma creatinine 0.6-10.8 mg/dL, mean: 1.3). Urinary activities of five tubular enzymes (alanine aminopeptidase, gamma-glutamyltransferase, alkaline phosphatase, lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase) increased significantly on the first day after the administration of contrast media, indicating a tubular damage. Glomerular filtration rate and the conventional tests of glomerular function (plasma creatinine, creatinine clearance, and urinary proteins) presented only slight variations after the administration of contrast media. In conclusion, contrast media principally affected the renal tubule (as demonstrated by enzymuria), while their effects on glomerular function were very mild.

Glomerular and tubular effects of contrast media diatrizoate and iopromide

The aim of this study is to evaluate the nephrotoxicity of two contrast media (CM), with different physicochemical characteristics: diatrizoate (ionic high-osmolar), iopromide (nonionic low-osmolar). Intravenous urography was performed in 34 patients: 17 were examined with diatrizoate and 17 with iopromide, randomly assigned. Different parameters of glomerular and tubular function were measured before and at 6, 24, and 48 h after urography. Both contrast media induced a reversible increase of urine enzymes, which was significantly higher after diatrizoate. In particular, diatrizoate determined a relevant increase of brush border enzymes gamma-glutamyltransferase (GGT) and alkaline phosphatase (ALP) and of cytosolic enzyme lactate dehydrogenase (LDH), while, after iopromide increases of urinary enzymes were less evident and were significant only for GGT and ALP. In addition, diatrizoate affected other tubular functions (clearances of phosphorus and uric acid) and slightly decreased glomerular function in a few patients. In no case did these glomerular and tubular effects have a clinical relevance. In conclusion, the nonionic low-osmolar contrast medium iopromide appeared less nephrotoxic than diatrizoate. The cost-benefit ratio needs further examination.

Effect of diatrizoate on the function of the isolated perfused rat kidney

The mechanism of the nephrotoxicity of water-soluble contrast media (WSCM) remains ill defined. We have studied the effect of diatrizoate on the isolated perfused rat kidney (IPRK). Emphasis was on the effect of low- and high-dose diatrizoate on glomerular filtration rate (GFR), renal perfusate flow (RPF), fractional excretion of albumin (FE Alb) and fractional reabsorption of sodium (FR Na). The addition of diatrizoate to the IPRK led to a dose-dependent biphasic change in RPF and GFR characterized by an initial transient increase followed by a marked and sustained decrease. Diatrizoate induced a diuresis and a parallel increase in urinary sodium excretion (fall of FR Na). Fe Alb was also increased in kidneys exposed to diatrizoate. Electron microscopy of a control kidney showed preservation of cellular architecture, which contrasted with the observed cytoplasmic vacuolation of proximal tubular cells after perfusion with diatrizoate. This study confirms a direct effect of WSCM on the function of the IPRK. In this experimental model, diatrizoate reproduces the effects observed in vivo on GFR and renal perfusion.

Contrast media nephrotoxicity: comparison of diatrizoate, ioxaglate, and iohexol after intravenous and renal arterial administration

In several studies in humans and animals it has been suggested that high osmolality and ionicity of contrast media are responsible for higher nephrotoxicity. To examine this suggestion, we evaluated the renal effects of three different contrast media--an ionic high osmolar, an ionic low osmolar, and a nonionic--following intravenous and renal arterial administration, in a population of 84 unselected, nondiabetic patients with adequate renal function. The results showed that the nephrotoxicity is minimal and equal for all three contrast media and for both routes of their administration, and it is concluded that in this category of patients the far higher cost of the newer low osmolar ionics and nonionics should be considered seriously in regard to nephrotoxicity.

Ioxaglate in paediatric angiocardiography

It is generally agreed that low osmolar contrast media are better tolerated than conventional media. This study examined both tolerance and image quality of ioxaglate in a group of paediatric patients undergoing angiocardiography for congenital heart disease. A consecutive series of 50 patients (mean age 5.47 years; range 4 days-14 years) were examined. The mean dose of ioxaglate administered per patient was 2.93 mL/kg. In general, ioxaglate was well tolerated. Three patients became febrile and another developed eosinophilia. Serum creatinine rose by a mean of 10 mumol/L. Significant renal dysfunction occurred in 12 patients with an increase in creatinine of 20-30 mumol/L. In no patient, however, were these effects a significant clinical problem. Diagnostic image quality was generally considered to be good with both cine-angiography and digital subtraction angiographic techniques.

A randomized comparison of the nephrotoxicity of iopamidol and diatrizoate in high risk patients undergoing cardiac angiography

Three hundred seven high risk patients with renal impairment (serum creatinine greater than or equal to 1.5 mg/dl) were randomized in a double-blind manner to either iopamidol (a nonionic, low osmolar radiocontrast agent) or diatrizoate (a conventional radiocontrast agent) at cardiac angiography with subsequent follow-up study of renal function. Baseline clinical and angiographic variables were similar in the iopamidol (n = 155) and diatrizoate (n = 152) groups. Change in renal function after angiography was less pronounced with iopamidol compared with diatrizoate as measured by mean ( +/- SD) increase in 24 h serum creatinine (0.11 +/- 0.2 versus 0.22 +/- 0.26 mg/dl, p less than 0.001), mean maximal increase in serum creatinine (0.2 +/- 0.44 versus 0.38 +/- 0.73 mg/dl, p less than 0.0001) and percent of patients with a maximal increase in serum creatinine greater than 0.5 mg/dl (8% versus 19%, p less than 0.01). Such differences could not be documented in diabetic patients using insulin. There was no significant difference between agents in the number of patients developing clinically severe acute renal dysfunction. It is concluded that iopamidol is less nephrotoxic than diatrizoate in high risk patients at cardiac angiography. However, the difference in nephrotoxicity is small, of no major clinical significance in the majority of high risk patients and could not be documented in insulin-using diabetic patients. Iopamidol may be the preferred agent in certain patients with advanced renal impairment, but further study is warranted.

Effects on renal hemodynamics and tubular function of the contrast medium iohexol in renal patients

Renal function was assessed in 20 (11 female and 9 male, age 21-76 years, mean 53) renal patients with a creatinine clearance 25-145 ml/min, mean 95, to evaluate the effects of iohexol, a non-ionic low-osmolar contrast medium. Intravenous urography was performed in 16 patients and computed body tomography in 4, using a dose of iohexol ranged between 0.6-3.3 (mean 1.17) g/kg b.w. Different parameters of renal function were determined in the week preceding and 1, 3 and 5 days after the administration of iohexol. The principal renal effect of iohexol was an increase of urinary alanine aminopeptidase, gamma-glutamyltransferase, lactate dehydrogenase, alkaline phosphatase and N-acetyl-beta-D-glucosaminidase. The maximum increase of enzymuria was observed on day 1 after the administration of iohexol. In most cases enzymes returned to base-line values within 3 days. No relevant variation of renal hemodynamics (glomerular filtration rate and effective renal plasma flow) was observed after iohexol. In conclusion, iohexol can increase of urinary enzymes, but the effect is rapidly reversible and is not accompanied by a clinically significant impairment of renal hemodynamics.

Contrast-associated nephropathy

Contrast nephropathy can be defined as an acute impairment of renal function that follows exposure to radiocontrast materials and for which alternative explanations for renal impairment have been eliminated. Based on reported studies, the incidence of contrast associated nephropathy (CAN) varies from 0 to 22%. This wide variation can be traced to differences in study design and the criteria used to designate significant renal impairment. Irrespective of the exact incidence, 2 defined risk factors have been identified: preexisting renal disease and diabetes mellitus. Whereas preexisting renal insufficiency is the single most influential risk factor for CAN, when diabetes coexists the incidence approaches 100%. The clinical presentation of CAN is distinct, having a temporal relation between the performance of the contrast study in the high-risk patient and the onset of an increase in serum creatinine levels within the next 24 hours. Serum creatinine values greater than 50% of baseline or rising 1 mg/dl or more is diagnostic. The peak serum creatinine level occurs within 3 to 5 days of the contrast study and oliguria is associated in approximately 30% of the cases. Monitoring serum creatinine is the most useful clinical procedure in high-risk patients after angiography. At least 5 potential pathophysiologic mechanisms of CAN have been proposed: interference with renal perfusion, altered glomerular perm-selectivity, direct tubular injury, intraluminal obstruction, and immunologic mechanisms. Support for each mechanism, either singularly or in combination, can be found in published reports; however, none has achieved universal acceptance. The single most important clinical axiom regarding the prevention and management of CAN is, "Always use the least invasive diagnostic procedure available."(ABSTRACT TRUNCATED AT 250 WORDS)

Low-osmolality contrast media: a current perspective

Intravascular radiographic contrast media play a major role in diagnostic imaging. Recently, low-osmolality contrast media (LOCM) have become available in the United States. Because of their lower osmolality, these new agents cause fewer undesirable physiologic effects and fewer adverse reactions than do conventional agents after intravascular administration. Unfortunately, the cost of LOCM is substantially higher than the cost of conventional contrast media. Appropriate use of these newer, more expensive contrast agents must be based on a thorough knowledge and understanding of their chemistry, physiologic features, and relative safety. Some questions remain about these new agents. Further studies are needed to determine the nephrotoxicity of LOCM relative to that of conventional agents. In addition, LOCM have less anticoagulant capacity than do the conventional media; therefore, clotting may occur when the LOCM and blood mix in syringes and small catheters. This potential decrease in anticoagulation and its clinical implications should be further investigated. Finally, the mortality rate associated with use of LOCM needs to be determined in future studies in large numbers of patients.

Acute renal failure associated with ioxaglate, a low-osmolality radiocontrast agent

Iodinated radiocontrast agents may cause acute renal failure, particularly in patients with preexisting renal failure, heart failure, or diabetes. The low-osmolality contrast agents cause less hypersensitivity, but substantial nephrotoxicity has not been noted. We report three high-risk patients who developed acute renal failure after one of these new agents, ioxaglate, was administered for coronary arteriography and ventriculography. The renal failure was severe: two of the patients required dialysis. We could find no previously reported cases of acute renal failure associated with ioxaglate. Despite their theoretical advantages, the low-osmolality contrast agents may cause acute renal failure in patients who are at risk and should be used with the same precautions as the conventional agents.

Comparative effects of nonionic (iopamidol) and ionic (sodium and meglumine diatrizoate) contrast media for urography on urinary excretion of water and solutes

Urinary water and solute excretion before and for 40 minutes after intravenous bolus injection of a nonionic (iopamidol) or an ionic medium (sodium meglumine diatrizoate) have been studied in subjects with normal renal function. Iopamidol produced less urinary losses of water, potassium, sodium, and chloride than did diatrizoate; uric acid excretion was also less enhanced. Surprisingly, both contrast agents produced a comparable increase in urinary pH and bicarbonate excretion. These data show that nonionic agents produce fewer changes in urinary excretion of water and solutes; the less enhanced excretion of uric acid after a nonionic medium may be an important reason to choose the latter agents for urography in patients at risk for urate neophropathy.

Intraarterial digital subtraction angiography of renal transplants

Nineteen renal allograft recipients with suspected vascular pathology of the graft were examined by digital subtraction angiography combined with intraarterial catheter technique. Image quality was excellent and diagnosis was definite in all cases. Dosages of contrast medium are reduced to a minimum (1.5 g iodine/patient) and the risk of nephrotoxic side effects is virtually negligible with this technique.

Acute renal failure in rats. Interaction between a contrast medium and renal arterial occlusion

Acute renal failure is a serious complication of reconstructive aortoiliac surgery. The question was raised whether its etiology includes interaction between preoperative angiographic contrast medium and intra-operative clamping of the renal arteries. Renal arteries of 180 rats were bilaterally clamped 10 to 120 min and serum urea was determined from 3 h to 7 days later. In 35 rats 40 min clamping alone produced an increase in urea reaching a maximum 1 day later (median increase 70%). In 3 groups of 12 rats intravenous injection of the contrast medium metrizoate alone in doses 1, 2 and 3 g I/kg body-weight produced no significant increase in urea. Intravenous injection of the same doses to 3 groups of 10 rats each followed 1 h later by renal arterial occlusion for 40 min produced median urea increases one day later of 110, 130 and 170 per cent, respectively, in the 3 groups. The increase was higher than that produced by contrast medium alone (p less than 0.01) or by renal artery clamping alone (p less than 0.05) indicating a potentiation of transient renal failure by the combination of contrast medium and renal arterial clamping.

Nephrotoxicity of ionic and non-ionic contrast media in aorto-femoral angiography

Nineteen patients examined with aorto-femoral angiography were randomized into two contrast medium groups (meglumine metrizoate and iohexol). Urine activity of beta-hexosaminidase, a specific renal enzyme, was determined before and on three occasions after angiography. No change of beta-hexosaminidase activity was found after angiography with iohexol, while there was a significant increase after examination with meglumine metrizoate. This indicates that meglumine metrizoate even following injection into the abdominal aorta damages renal cells which could not be shown with iohexol as contrast medium. We therefore recommend that at least patients with impaired renal function should be examined with the non-ionic contrast medium iohexol to minimize the danger of further damage to the kidneys and a possible renal failure.

Digital subtraction angiography in renal transplant recipients

The renal transplant vascularity of 72 patients was investigated by intravenous digital subtraction angiography (IV DSA). The procedure was combined with selective venous renin sampling of the transplant and native kidneys to identify the source of hypertension in these patients. Abnormalities were found on IV DSA examination in 26 patients, of whom 7 had graft artery stenosis, 7 had diffuse intrarenal narrowing, 9 had lower pole ischemia, and 3 had aneurysmal dilatation. The combined outpatient procedure was well tolerated by all patients with no complications nor incidence of proteinuria.