Pyelorenal backflow during retrograde pyelography in normal and ischemic porcine kidneys. A radiologic and pathoanatomic study.

Retrograde pyelography was performed in 14 kidneys of anesthetized baby pigs to study the phenomenon of pyelorenal backflow. In this model, a constant retrograde perfusion rate of 10 ml/min was used which resulted in a progressive increase in pelvic pressure. The experiments were done on normal and ischemic kidneys. Pyelosinous backflow developed in twelve kidneys at an average intrapelvic pressure of 197 mm Hg and was independent of renal ischemia. Intrarenal backflow was observed only in kidneys which had been ischemic for 60 min and after 2 h of hypotension, or in postmortem kidneys. Intrarenal backflow in one or two papillae occurred at an intrapelvic pressure of 125 mm Hg. At higher intrapelvic pressures there was more intense and widespread intrarenal backflow. Histologic examination revealed tears in the calyceal fornix in cases with pyelosinous backflow. If intrarenal backflow was present there was parenchymal necrosis, interstitial Ferritin (added to the contrast material) in the papilla and in the corticomedullary junction, and tears leading from the pelvic cavity into the renal parenchyma.