Intrarenal pressure during ex-vivo flexible ureteroscopy: a pilot experimental study in cadaveric kidneys

Due to donor shortages, organ donation criteria have been expanded, and transplant societies encourage acceptance of kidneys with stones. Ex-vivo flexible ureteroscopy (eFURS) in these grafts is increasing. Although the technique is considered feasible, intrarenal pressure (IRP) during eFURS has not been characterized. This pilot study aimed to characterize IRP under different procedural conditions using a non-perfused cadaveric kidney model of eFURS and to describe associated ureteral findings.

Eight cadaveric kidneys were harvested, and eFURS was performed under four experimental conditions: direct insertion (A), ligated ureter (B), and use of 10-12Fr (C) and 12-14Fr (D) ureteral access-sheaths (UAS). IRP was measured using a pressure sensor over 10 min, at baseline and during irrigation (continuous and manual).

Most ureters showed limited compliance, making UAS insertion difficult. Baseline IRP ranged from 0 to 6mmHg. With continuous irrigation, IRP was highest in procedure B (up to 31mmHg), increasing further with added manual irrigation (up to 105mmHg), and peaking during high-pressure irrigation (HPI) (200mmHg). The lowest IRP during HPI was observed in procedures A (130mmHg), C (85mmHg), and D (50mmHg). Overall, IRP was consistently highest when the ureter was ligated (9-62mmHg) and lowest when using a UAS, especially the 12-14Fr (6-25mmHg). Ureteral lesions were observed after the procedures, all located in the pelvic ureter and occurring in the least compliant ureters.

In this non-perfused cadaveric model, UAS use was associated with lower IRP, particularly with the 12-14Fr UAS, although the larger sheath could not be inserted in all ureters. Macroscopic ureteral lesions were observed after completion of the experimental protocol but could not be attributed to a specific procedure or UAS size. These findings are descriptive and hypothesis-generating.