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 dilation and ureteroscopy were examined in 26 renoureteral units in 13 minipigs. Acutely, ureters subjected to mechanical (bougie, Teflon, or balloon) ureteral dilation and ureteropyeloscopy (UPS) demonstrated active mucosal bleeding with multiple sites of perforation, whereas ureters subjected to hydraulic dilation and UPS were significantly less traumatized. 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 evidence of obstruction had resolved in the mechanically dilated group. While 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 measured continuously with a nephrostomy catheter in vivo during (bougie, Teflon, balloon and hydraulic) ureteral dilation and UPS. Renal pelvic pressure during rigid ureteroscopy approximated the resting pelvic pressure plus the irrigant height above the kidney or set pressure on a hydraulic 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 ureter without flow. The effects on RPP of continuous bladder drainage with a uretheral catheter and renal pelvic decompression with an open-ended ureteral catheter passed into the renal pelvis through the ureteroscope working channel were also examined. The maximum RPP was evaluated 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. Hg) RPP on renal histology. Acutely, high pressure caused diffuse denudation and flattening of the caliceal urothelium, submucosal edema and congestion not seen in calyces subjected to low irrigant pressure. Four to six weeks later, there was a higher incidence of columnar metaplasia, subepithelial nests and pericalyceal vasculitis in calyces subjected to high pressure as compared with those subjected to low irrigant pressure. Acutely, renal tubules subjected to high irrigant pressure demonstrated marked vacuolization and degeneration, whereas tubules subjected to low pressure appeared normal. At 4 to 6 weeks, focal scarring was seen in 5 of 7 kidneys subjected to high irrigant pressure, whereas no scarring was noted in all 6 kidneys subjected to low irrigant pressure.(ABSTRACT TRUNCATED AT 400 WORDS)