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).