Intrarenal hemodynamics and renal function in postobstructive uropathy.

: Impairment of renal function was noted after release of 24 hr of unilateral (UUO) and bilateral (BUO) ureteral obstruction. After release of obstruction fractional sodium excretion was identical in both obstructed and intact kidney of UUO rats, whereas massive natriuresis occurred in BUO rats. Renal blood flow in BUO rats, determined by the microsphere method after released of 24 h of obstruction, was approximately 60 per cent of control values. Mean renal blood flow of the obstructed kidney of UUO rats after release of obstruction was 78 per cent of the mean renal blood flow of the contralateral unobstructed kidney. No redistribution of intrarenal blood flow was noted in UUO and BUO rats. Filtration fractions of obstructed kidneys from BUO and UUO rats after release of obstruction were lower than those of controls, suggesting that preglomerular vasoconstriction is primarily involved in the reduction of glomerular filtration rate.