MORPHOLOGICAL AND PHYSIOLOGICAL-CHANGES IN THE URINARY-TRACT ASSOCIATED WITH URETERAL DILATION AND URETEROPYELOSCOPY - AN EXPERIMENTAL-STUDY

The gross and microscopic effects of four common modes of ureteral dil ation and ureteroscopy were examined in 26 renoureteral units in 13 mi nipigs. Acutely, ureters subjected to mechanical (bougie, Teflon, or b alloon) ureteral dilation and ureteropyeloscopy (UPS) demonstrated act ive mucosal bleeding with multiple sites of perforation, whereas urete rs subjected to hydraulic dilation and UPS were significantly less tra umatized. Two weeks after mechanical ureteral dilation and UPS, 3 of 6 ureters were obstructed radiographically, whereas all 7 hydraulically dilated ureters were unobstructed. By 6 weeks, all radiographic evide nce of obstruction had resolved in the mechanically dilated group. Whi le 5 of 6 mechanically dilated ureters showed extensive scarring with muscle loss 4 to 6 weeks after dilation, no scarring was seen in those ureters dilated hydraulically. Renal pelvic pressure (RPP) was measur ed continuously with a nephrostomy catheter in vivo during (bougie, Te flon, balloon and hydraulic) ureteral dilation and UPS. Renal pelvic p ressure during rigid ureteroscopy approximated the resting pelvic pres sure plus the irrigant height above the kidney or set pressure on a hy draulic pump, plus a ''scope effect'' which was characterized by a 20 to 25 mm. Hg increase in RPP produced by moving the endoscope in the u reter without flow. The effects on RPP of continuous bladder drainage with a urethral catheter and renal pelvic decompression with an open-e nded ureteral catheter passed into the renal pelvis through the ureter oscope working channel were also examined. The maximum RPP was evaluat ed in vitro in a separate group of 16 freshly harvested pig kidneys of similar weight examined immediately after sacrifice and was found to be 439 mm. Hg. We also studied the immediate and long-term effects of low (<120 cm. H2O or 90 mm. Hg) versus high (>200 cm. H2O or 150 mm. H g) RPP on renal histology. Acutely, high pressure caused diffuse denud ation and flattening of the caliceal urothelium, submucosal edema and congestion not seen in calyces subjected to low irrigant pressure. Fou r to six weeks later, there was a higher incidence of columnar metapla sia, subepithelial nests and pericalyceal vasculitis in calyces subjec ted to high pressure as compared with those subjected to low irrigant pressure. Acutely, renal tubules subjected to high irrigant pressure d emonstrated marked vacuolization and degeneration, whereas tubules sub jected to low pressure appeared normal. At 4 to 6 weeks, focal scarrin g was seen in 5 of 7 kidneys subjected to high irrigant pressure, wher eas no scarring was noted in all 6 kidneys subjected to low irrigant p ressure. In summary, it seems that hydraulic intramural ureteral dilat ion is less traumatic than mechanical modes of dilation with less pote ntial for ureteral scarring and stricture. Prolonged exposure of the m inipig kidney to high RPP (>200 cm. H2O) during UPS resulted in renal scarring and inflammation not seen following low pressure (<120 cm. H2 O) irrigation. Because the human kidney is anatomically and physiologi cally similar to the minipig kidney, it may respond to high renal pelv ic pressures in a similar fashion.