The effect of irrigation rate on intrarenal pressure in an ex vivo porcine kidney model-preliminary study with different flexible ureteroscopes and ureteral access sheaths.

INTRODUCTION: Ureteral access sheath (UAS) and irrigation are used in flexible ureteroscopy (fURS). Both conventional UAS (cUAS) and vacuum-assisted UAS (vaUAS) are currently available. Irrigation increases the intrarenal pressure (IRP). Our objectives were to study the effects of various irrigation rates on IRP using different sizes of fURS in different sizes and functions of UAS. MATERIALS AND METHODS: Ten freshly harvested porcine kidneys served as the study subjects. 11/13F and 12/14F cUAS and vaUAS with 2.8 mm and 3.2 mm fURS were experimented on in various scope/sheath combinations. 6F pressure monitor catheters were placed into upper, middle, and lower calyces. IRPs were recorded under different irrigation rates in cUAS and vaUAS, with either 150 or 300 mmHg aspiration pressures, and with air vent either open or closed. RESULTS: 12/14F cUAS with 2.8 mm fURS could maintain IRPs below 35 mmHg with irrigation rates up to 200 cc/min. With 3.2 mm fURS, the rate dropped to 110-120 cc/min. With 12/14F vaUAS and vent closed, the IRP remained less than 5 mmHg at 200 cc/min irrigation for both fURS. For 11/13F cUAS, the < 35 mmHg threshold for 2.8 mm fURS was 80-90 cc/min; for 3.2 mm fURS, it was 30-40 cc/min. For 11/13F vaUAS with vent closed, IRPs remained < 5 mmHg at 200 cc/min irrigation for both scopes. CONCLUSION: Both 12F cUAS and vaUAS can be used safely with 2.8 mm fURS up to 200 cc/min irrigation. With either a smaller sheath or a larger scope, vaUAS with vent closed can maintain IRP in a safe range up 200 cc/min irrigation. vaUAS with vent open performed marginally better than cUAS.