Optimizing flexible and navigable ureteral access sheaths (FANS) manoeuvrability: the impact of sheath size, working channel occupancy and deflection technique – an EAU endourology in vitro analysis

Abstract Introduction Conventional ureteral access sheaths are placed below the ureteropelvic junction (UPJ), whereas the novel flexible and navigable suction ureteral access sheaths (FANS) are navigated across the UPJ with its distal tip deflected into target calyx under endoscopic guidance to facilitate stone fragments suctioning. We evaluate how FANS deflection angles are affected by sheath sizes, occupancy of working channel (WC) (empty, occupied by Olympus Soltive™ Thulium Laser Fiber 150 μm and 200 μm core diameter) and deflection techniques (ureteroscope deflection versus sheath advancement) across four brands of FANS. Materials & methods In-vitro deflection angles of brand new FANS (sheath sizes 10/12Fr, 11/13Fr and 12/14Fr) ClearPetra (Well Lead Medical Co., Ltd, China) 46 cm, Elephant II (YiGao Medical Technology Co., Ltd, China) 50 cm, Innovex (Innovex Medical Co., Ltd, Shanghai, China) 50 cm, and Reborn (Hunan Reborn Medical Science and Technology Development Co., Ltd, China) 50 cm with brand new single-use flexible ureteroscope Pusen Uscope 7.5Fr PU3033A (Zhuhai Pusen Medical Technology Co., Ltd. Guangzhou, China) were measured in triplicate with varied WC occupancy and forementioned techniques. Maximum deflection angle was expressed as a mean of 3 measurements. One-way ANOVA test was performed for comparisons of the effect of sheath sizes, sheath brands, working channel occupancy, and different deflection techniques. Four-way ANOVA test was performed to evaluate the influence of the aforementioned four factors on the maximal deflection angle, with analysis on the main effects and interaction. For all tests, a two-sided p-value less than 0.05 was considered statistically significant. Statistical tests were performed with SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Results 10/12Fr and 11/13Fr sheath sizes have significantly better deflection angles than 12/14Fr across all brands with a 7.5Fr flexible ureteroscope. Sheath advancement technique was significantly better with ureteroscope deflection technique. There is no significant difference in deflection angles with occupancy of 150–200 μm fiber. Conclusion Gaining better understanding of the performance of FANS can ultimately guide clinicians in their selection and optimal utilization of the instrument to enhance procedural efficacy and treatment outcomes.