Intrarenal hemodynamics and ureteral pressure during ureteral obstruction.

Renal blood flow was measured in bilateral ureteral obstruction (BUO) and unilateral ureteral (UUO) obstruction. Renal blood flow of BUO and UUO rats before release of 24-hr obstruction was approximately 69 per cent and 77 per cent of control values, respectively. No redistribution of intrarenal blood flow was noted in UUO and BUO rats. Prerelease ureteral pressure of BUO rats (27.6 +/- 1.60 mm Hg) was significantly higher than that of UUO rats (14.4 +/- 1.30 mm Hg, P less than 0.001). Although the blood urea nitrogen of UUO rats with urine reinfusion was similar to that of BUO rats, the ureteral pressure was 14.8 +/- 1.93 mm Hg. Therefore, the higher ureteral pressure of BUO rats is not due to elevation of blood urea nitrogen. It is concluded that decreased renal blood flow during obstruction and high ureteral pressure may result in more severe tubular damage in BUO than in UUO. The decreased renal perfusion is probably due to changes in intrarenal vascular tone rather than due to intersitial pressure.