Evaluation of fluid absorption during flexible ureteroscopy in an in vivo porcine model.

OBJECTIVE: To evaluate the relationship between renal pelvis pressure and fluid absorption during ureteroscopy (URS) in a live porcine model. MATERIALS AND METHODS: Flexible URS (fURS) was performed in anaesthetised female Yorkshire pigs. Prior to performing fURS, a 0.3556-mm (0.014″) pressure-sensing guidewire (Comet™, Boston Scientific) was placed to monitor renal pelvis pressure. A simulated fURS procedure was then performed for 1 h. Infusion of irrigation fluid (5% ethanol in saline) at target renal pelvis pressures (37-150 mmHg) was maintained for 1 h using a pressure bag and real-time feedback from the pressure-sensing guidewire. Venous blood was sampled every 10 min. The volume of irrigation fluid absorbed was estimated with established equations. RESULTS: A URS procedure was performed in vivo in 18 porcine kidneys and the volume of irrigation fluid absorbed during the 1 h URS was calculated. The mean (SD) volume of irrigation fluid absorbed after 1 h of simulated URS was 7.6 (5.7), 10.8 (7.1), 26.0 (15.8), and 56.8 (22.3) mL at renal pelvis pressures of 37, 55, 75, and 150 mmHg, respectively. Compared with URS with renal pelvis pressure of 37 mmHg, the volume of fluid absorption was significantly greater at renal pelvis pressures of 75 and 150 mmHg (P = 0.026 and P = 0.047, respectively). In addition, compared with URS with renal pelvis pressure of 37 mmHg, the rate of absorption was significantly greater at renal pelvis pressures of 75 and 150 mmHg (both P < 0.001). CONCLUSION: In this study of an in vivo porcine model of URS, increasing renal pelvis pressures during URS were associated with increases in irrigation fluid absorption and increases in the rate of fluid absorption.