Intrarenal pressure study using 7.5 French flexible ureteroscope with or without ureteral access sheath in an ex-vivo porcine kidney model.

Abstract

7.5F digital fURS and 9.5/11.5F ureteral access sheaths (UAS), both conventional (cUAS) and vacuum-assisted (vaUAS), are commercially available. Irrigation increases intrarenal pressure (IRP). This study analyzes the IRP with various irrigation rates using 7.5F fURS without UAS or with either cUAS or vaUAS in an ex-vivo porcine model. Pyelo-tubular backflow was also studied during these experiments. 11 porcine kidneys were used. 7.5F digital fURS was tested without UAS and with 9.5/11.5F cUAS and vaUAS. 6F pressure monitor catheters were placed into the upper and lower calyces. IRPs were recorded under different irrigation rates. When vaUAS was used, the air vent was either open or closed. 300mmHg aspiration pressure was chosen. Lastly, contrasted irrigation fluid was delivered until IRP reached above 30mmHg. Fluoroscopy images were obtained at 5mmHg intervals over this threshold to study the pyelo-tubular backflow. Using cUAS, IRP reached 30mmHg with irrigation rates between 60 and 70cc/min. Using vaUAS with vent closed, IRP never exceeded 10mmHg with irrigation up to 120cc/min. vaUAS with vent open performed marginally better than cUAS. fURS without UAS performed better than cUAS. Pyelo-tubular backflow became prominent at 40mmHg. In an ex-vivo porcine model, 7.5F fURS could be used safely without UAS with irrigation rates up to 120cc/min. The safety margin dropped to 60-70cc/min with cUAS. vaUAS with vent closed maintained IRP < 10mmHg with irrigation rates up to 120cc/min. Pyelo-tubular backflow was observed with IRP > 35mmHg.