The influence of contrast medium dose on filtration fraction in the rabbit kidney

We have examined the effect of dose on contrast medium-induced reductions in glomerular filtration in anesthetized rabbits. The fraction of renal plasma flow that is filtered, the filtration fraction, was directly measured by the renal arteriovenous difference method using technetium-99m (99mTc) (Sn) DTPA as the tracer, arterial and renal venous extracorporeal shunts, a gamma camera and a computer. Filtration fraction (FF) was measured each 30 seconds before and after contrast medium (sodium/methylglucamine diatrizoate) was injected in 15 seconds at a dose of 0.5, 1.0 or 2.0 ml/kg, IV. In six animals that had a control FF of 0.19 +/- 0.01 there was a dose-related decrease in FF. The largest dose reduced FF by 53.3%. In three other animals that had a low control FF (0.07 +/- 0.01), the largest dose induced an even greater 71.0% decrease in FF. These data suggest that attempts at increasing contrast excretion by injecting larger doses will be offset, at least in part, by larger reductions in glomerular filtration, and that this effect may be greater when glomerular function is impaired.