Relationship between renal blood flow and ureteral pressure during 18 hours of total unilateral uretheral occlusion. Implications for changing sites of increased renal resistance.

Continuous monitoring of ipsilateral renal blood flow and ureteral pressure during 18 hr of complete unilateral ureteral occlusion in five awake dogs defined the onset of preglomerular vasoconstriction, characteristic of chronic ureteral occlusion. There was a triphasic relationship between ipsilateral renal blood flow and ureteral pressure during the 18 hr of acute ureteral occlusion: (i) 0 to 1 1/2 hr, renal blood flow and ureteral pressure rose; (ii) 1 1/2 to 5 hr, renal blood flow fell while ureteral pressure continued rising; (iii) 5 to 18 hr, renal blood flow and ureteral pressure fell together. These relationships suggest different pathophysiologic mechanisms changing renal vascular resistance during the first 18 hr of complete ureteral occlusion, with increased preglomerular resistance occurring after 5 hr and being dominant in chronic ureteral occlusion.