Histological changes caused by the prolonged placement of ureteral access sheaths: an experimental study in porcine model.

The objective is to evaluate the histological damage to the ureteral wall caused by the prolonged placement of an access sheath in porcine model. Six ureters from three female pigs were randomized into three groups. In each group, an UAS with different indwelling time was inserted. 9.5/11.5 Fr Flexor ureteral access sheaths were inserted in both ureters with left indwelling for 30 min and right for 60 min. The ureteral access sheath was advanced up to the proximal ureter. No resistance was observed during the insertion. Ureters were harvested in immediately after the sheath placement process in one pig. The ureters of the remaining two pigs were removed at 1 and 2 weeks after the procedure, respectively. Histological examination took place also in these specimens. Ureters with an indwelling time of 30 min: histological examination of the ureter after immediate dissection revealed signs of acute inflammation at the distal ureter. The ureter dissected at 1 week showed minimal focal transmural inflammation along its length with minimal epithelial hyperplasia. The ureter dissected at 2 weeks, no signs of inflammation. Ureters with an indwelling time of 60 min: histological examination of the immediately dissected ureter revealed signs of acute inflammation at the distal ureter. At 1 week, chronic transmural inflammation was predominantly observed in the distal ureter. At 2 weeks, minimal transmural inflammation was observed. The use of UAS did not cause any severe histological damage on porcine ureters. Acute signs of inflammation gradually recovered within 2 weeks.