Low-osmolality contrast media and the risk of contrast-associated nephrotoxicity

The authors review clinical data, including those from the recent Iohexol Cooperative Group trial, regarding the nephrotoxic potential of low-osmolar versus high-osmolar contrast media. The clinical characteristics and postulated mechanisms of contrast-associated nephrotoxicity are also considered.

The principal strategy for identifying relevant articles was to search the MEDLINE database using the MeSH heading "contrast media nephrotoxicity." Articles from 1966 through 1992 that were considered included original research papers as well as reviews. Those articles selected for detailed review documented original research pertaining to use of low-osmolar or high-osmolar agents. Selected abstracts for pertinent society meetings were also used. No attempt was made to be complete in describing the field. Rather, specific articles that selectively address the question of nephrotoxicity related to the osmolar content of contrast media were used for discussion.

In-vitro and animal studies indicate that renal changes possibly involved in the pathogenesis of contrast-associated nephrotoxicity seem to be ameliorated with low-osmolar contrast media, compared with high-osmolar agents. Several recent clinical trials, as well as a meta-analysis combining 24 randomized studies, suggest that the risk of contrast-associated nephrotoxicity is similarly low with high-osmolar and low-osmolar agents among otherwise stable patients with normal renal function, but that low-osmolar contrast is less nephrotoxic than media with high osmolality in patients with pre-existing renal insufficiency.