Renal haemodynamics prior to and after release of 24 hr unilateral ureteral ligation in the dog.

Renal functional parameters were investigated prior to and following release of 24 hr unilateral ureteral ligation (UUL). In the obstructd kidney renal blood flow (RBF) and glomerular filtration rate (GFR) decreased to about 50% and 14%, respectively, as compared to normal controls. Relief of the obstruction did not cause any change in renal haemodynamic parameters in the ligated kidney. Urine flow rate and urine osmolality in the previously obstructed kidney were decreased, the excreted fraction of filtered sodium increased as compared to the undisturbed kidney. The excretory lesion of the obstructed kidney is due to arteriolar, presumably preglomerular, vasoconstriction. Radioactive microspheres revealed that the decrease of RBF in the obstructed kidney was caused by diminished perfusion of the outer cortical zones, while blood flow to the inner cortical zones was unaltered. Fractional flow to the outer cortex was decreased, that to the inner cortex increased as compared with normal controls. In the undisturbed kidney there was a shifting of flow from the outer towards the inner cortex, while total blood flow remained unaltered.