Partial unilateral ureteric obstruction alters regional renal blood flow

Complete unilateral ureteric obstruction decreases ipsi-lateral and increases contra-lateral renal blood flow, with shunting of intrarenal blood flow from outer to inner cortical zones. We tested the hypothesis that partial unilateral ureteric obstruction would also result in alterations in renal perfusion patterns. In five dogs, the left ureter was partially obstructed for 4 weeks and then reimplanted into the bladder for a further 4 weeks. Whitaker tests confirmed partial ureteric obstruction. Renal blood flow was assessed at each stage by distribution of radioactively labelled microspheres prior to and following ureteric obstruction and after reimplantation. Partial unilateral ureteric obstruction significantly decreased total blood flow to the ipsi-lateral kidney (51% vs 26%;P<0.05) and increases total blood flow to the contralateral kidney (49% vs 74%;P<0.05). In the ipsilateral kidney, partial ureteric obstruction induced a significant decrease in outer cortical blood flow (57% vs 76%;P<0.01) and a concomitant increase in inner cortical blood flow (35% vs 18%;P<0.02). A similar, albeit less marked, shunting of blood from outer to inner cortex was seen in the contralateral kidney. Relief of sbstruction after 4 weeks did not restore the renal circulation to its pre-obstruction profile. We speculate that the alterations in intrarenal blood flow may be hormonally mediated.