In Vitro Study Of Flexible Vacuum-Assisted Ureteral Access Sheath

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:A manometric model was established in porcine kidneys to observe the change in intrarenal pressure（IRP）in the FV-UAS（12/14Fr）and traditional UAS（12/14Fr）groups at different irrigation fluid velocities of 30,50,80,and 100 m L/min.Establish a kidney stone model（with 0.2 g,dry,≤5 mm stones）to simulate RIRS.A total of 20 porcine kidneys were randomly 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%’’].Stone volume was obtained by CT pre-and postoperatively.Results:FV-UAS can follow flexible ureteroscopy（f-URS）to cross the ureteropelvic junction（UPJ）and into the renal pelvis and calices.FV-UAS can actively make IRP<10 cm H₂O by adjusting the negative values at different irrigation fluid velocities.The mean residual stone volume of the FV-UAS vs traditional UAS groups was 33.7 vs 92.5 mm3（p=0.017）.The mean stone volume clearance rates of the FV-UAS vs traditional UAS groups were 98.5%and 95.9%,respectively（p=0.017）.Seven cases achieved complete stone-free status in the FV-UAS group.All patients had residual fragments postoperatively in the traditional UAS group.Conclusions: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 seven of the ten kidneys were completely free of stone fragments.