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.

Abstract

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. Ten freshly harvested porcine kidneys served as the study subjects. 11/13F and 12/14F cUAS and vaUAS with 2.8mm and 3.2mm 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 300mmHg aspiration pressures, and with air vent either open or closed. 12/14F cUAS with 2.8mm fURS could maintain IRPs below 35mmHg with irrigation rates up to 200cc/min. With 3.2mm fURS, the rate dropped to 110-120cc/min. With 12/14F vaUAS and vent closed, the IRP remained less than 5mmHg at 200cc/min irrigation for both fURS. For 11/13F cUAS, the < 35mmHg threshold for 2.8mm fURS was 80-90cc/min; for 3.2mm fURS, it was 30-40cc/min. For 11/13F vaUAS with vent closed, IRPs remained < 5mmHg at 200cc/min irrigation for both scopes. Both 12F cUAS and vaUAS can be used safely with 2.8mm fURS up to 200cc/min irrigation. With either a smaller sheath or a larger scope, vaUAS with vent closed can maintain IRP in a safe range up 200cc/min irrigation. vaUAS with vent open performed marginally better than cUAS.