Effects of contrast media on renal function and subcellular morphology in the dog

: The effects of intravenous contrast media (CM) on renal excretory function and subcellular morphology are examined in this animal investigation. A decrease in GFR (12.0 +/- 1.6 vs. control 30.2 +/- 2.5 ml/min) was observed when renal function was evaluated by means of the artero-venous extraction method with Tc99m DTPA and the anticipated inverse relationship to urinary flow (Vml/min) noted. An artifactual increase in GFR (43.5 +/- 10.0 vs. control 39.1 +/- 3.8 ml/min) was observed using the timed urinary clearance of inulin. V(ml/min) increased four-fold (0.6 +/- 0.16 control vs. 2.7 +/- 0.7 ml/min; P less than .05) over the first five minutes after injection of CM. Urine osmolality initially approached isotonicity and then returned toward preinjection values. Osmolal clearance (Cosm) rose 2.5 times (1.4 +/- 0.3 control vs. 3.7 +/- 1.0 ml/min; P less than .05). The fractional excretion of both Na+ (FENa+) and K+ (FEK+) increased. A comparison of urinary osmolality vs. time after injection of CM confirms a nonspecific osmotic effect on tubular (and hence total urine) flow. The hemodynamic effects of CM on the kidney via the i.v. route reflect a predominant and nonspecific osmotically mediated vasodilation. No significant light or electron microscopic changes were observed. These findings suggest that the major renal physiologic actions of hypertonic CM are a nonspecific response to agent osmolality.