Gadolinium contrast media are more nephrotoxic than iodine media. The importance of osmolality in direct renal artery injections

A study was undertaken of the role of osmotoxicity in gadolinium (Gd) and iodine contrast media (CM) nephrotoxicity in ischemic porcine kidneys. Test solutions: mannitol iso-osmotic to 0.5 M gadopentetate (1.96 Osm/kg H₂O), 0.5 M gadodiamide (0.78 Osm/kg H₂O) and 0.5 M iohexol (190 mg I/ml, 0.42 Osm/kg H₂O). Each solution was injected [3 ml/kg body weight (BW)] into the balloon-occluded (10 min) renal artery of eight left-sided nephrectomized pigs. The plasma half-life of a glomerular filtration rate (GFR) marker was used to compare their effects on GFR 1–3 h post-injection. The median half-lives of the GFR marker after injection of gadopentetate (1,730 min) and mannitol 1.96 Osm/kg H₂O (2,782 min) did not differ statistically (P=0.28), but were significantly longer than after all other solutions (P<0.001). There was no significant difference (P=0.06) between gadodiamide (218 min) and mannitol 0.82 Osm/kg H₂O (169 min), while there was (P=0.03) between iohexol (181 min) and mannitol 0.43 Osm/kg H₂O (148 min). The difference between gadodiamide and iohexol was significant (P=0.01). Reduction in GFR, as a marker of nephrotoxicity, induced by gadopentetate correlated with its high osmolality, while the effect of gadodiamide and iohexol may include chemotoxicity. Iohexol molecules were less nephrotoxic than the Gd-CM molecules and contain three-times the number of attenuating atoms per molecule.