LAUSR

OBJECTIVES To compare the safety and effectiveness of a novel flexible vacuum-assisted ureteral access sheath (FV-UAS) and traditional ureteral access sheath (UAS) in simulating retrograde intrarenal surgery (RIRS). MATERIALS AND METHODS Amanometric model was established in porcine kidneys to observe the change inintrarenal pressure in the FV-UAS and traditional UAS groups at different irrigation fluid velocities of 30 ml/min, 50 ml/min, 80 ml/min, and 100 ml/min. Establish a kidney stone model (with 0.2 g, dry, ≤ 5 mm stones) to simulate RIRS. A total of 20 porcine kidneys wererandomly numbered from 1 to 20 (FV-UAS group, 1-10; traditional UAS group, 11-20). The stone volume clearance rate and operation time were compared between the two groups. [" Stone volume clearance rate= (1-(residual stone volume)/(preoperative stone volume))×100%" )]. Stones volume was obtained by computed tomography (CT) preoperatively and postoperatively. RESULTS FV-UAS can follow flexible ureteroscopy (f-URS) to cross the ureteropelvic junction (UPJ) and into the renal pelvis and calyces. FV-UAS can actively make intrarenal pressure (IRP) less than 10 cmH2O by adjusting the negative values atdifferent irrigation fluid velocities. The mean residual stone volume of the FV-UAS vs. traditional UAS groups was33.7 mm3 vs. 92.5 mm3 (P = 0.017). The mean stone volume clearance rates of the FV-UAS vs. traditional UAS groups were 98.5 % and95.9 %, respectively (P = 0.017). Seven cases achieved complete stone-free status in the FV-UAS group. All patients hadresidual fragments postoperatively in the traditional UAS group. CONCLUSIONS FV-UAS can follow f-URS to cross the UPJ and into the renal pelvis and calyces, avoiding the interference of UPJ in controlling IRP. FV-UAS can actively control the IRP to be reduced to the desired range by adjusting the negative value under any irrigation fluid velocity. FV-UAS close to the stone can achieve complete stone-free in RIRS.