Pyelorenal backflow in rabbits following clamping of the renal vein and artery: radiologic and microscopic investigation.

Retrograde pyelography was carried out in rabbits during and following temporary clamping of either the renal artery and vein together or the main renal vein alone. Pyelosinous backflow was observed in all kidneys and pyelovenous backflow in 16 of the 18 kidneys, occurring at intrapelvic pressures between 50 and 100 mmHg. During simultaneous complete renal artery and vein occlusion intrarenal backflow occurred in all 3 kidneys examined while it was observed in 3 of 6 kidneys when the pyelography was performed 5 min after removal of the clamp. During complete renal vein occlusion filling with contrast medium of the central intrarenal veins occurred in all 3 kidneys but only in 3 of 6 kidneys examined after the clamp had been removed. Microscopically, pyelosinous backflow was explained by vital tears in the fornix of the pelvic cavity. Tears extending into the kidney parenchyma were only observed in kidneys with intrarenal backflow at pyelography.