The nephrogram of normovolemic, renal artery hypotension

Experimental hemorrhagic hypotension results in a prolonged nephrogram during excretory urography. We evaluated the effect of reduced renal perfusion pressure on the nephrogram in normovolemic dogs. Renal artery perfusion pressure to one kidney was reduced to 40-50 mm Hg by inflating a renal artery balloon catheter. Subsequent urograms were qualitatively assessed for nephrographic density. Plasma and urinary iodine concentrations were determined by fluorescent excitation analysis. Total renal blood flow (TRBF) and its intrarenal distribution were assessed with isotopically labeled microspheres. In the majority of dogs severe oliguria and a prolonged and increasingly dense nephrogram were produced in the kidney exposed to reduced perfusion pressure. The nephrogram of the contralateral, normotensive kidney rapidly diminished in density, associated with the excretion of a large volume of dilute urine. The total urinary iodine excreted in 60 min was significantly less than that excreted by both kidneys in control experiments. TRBF to the hypotensive kidney was significantly reduced from its control level, and the percentage of TRBF perfusing the outer cortex decreased.