Can We Provide Low Intrarenal Pressures with Good Irrigation Flow by Decreasing the Size of Ureteral Access Sheaths?

Flexible ureterorenoscopy (F-URS) plays a major role in the management of kidney stones. Ureteral access sheaths (UAS) are important tools for F-URS. In this study, we aimed to evaluate the difference in intrarenal pressures between different flexible ureteroscopes while using the same UAS and to calculate the irrigation flow variance. Eight different flexible ureteroscopes were tested with five different UAS on an artificial kidney model to measure intrarenal pressures and irrigation flow. Irrigation at 60 cmH2O pressure was performed; the pressure and the irrigation flow amount were recorded with different states of the operator channel: Free, with the laser fiber (272 μm), and with the nitinol basket (1.9F) inside. The highest pressure recorded was 46.68 cmH2O with Wolf Boa and 9.5/11.5F Cook Medical UAS. All the ureteroscopes that fit inside the 10/12F Coloplast ReTrace provided pressures below 40 cmH2O. The inner diameter of the 10/12F Rocamed Bi-Flex is actually 11F, so intrarenal pressures were lower and irrigation flow was higher. With the 11/13F Boston Scientific Navigator HD and 12/14F Coloplast ReTrace, the pressures were very low. The irrigation flow measurements were in concordance with pressure measurements. The ureteroscope sizes diminished with advancements in technology. Small-sized ureteroscopes can provide low intrarenal pressures with good irrigation flow when used with convenient small-sized access sheaths. The compatibility between the ureteroscopes and UASs should be anticipated by all endourologists and considered during F-URS. The advantages of 10/12 UASs in terms of intrarenal pressure and irrigational flow should make these access sheaths an interesting first-line choice.