Impact of Ureteral Access Sheath Size During Flexible Ureteroscopy Using a 6 o'clock Working Channel: A Prospective...

The impact of ureteral access sheath (UAS) size on surgical outcomes in flexible ureteroscopy (f-URS) remains controversial, particularly with modern suction-assisted techniques and evolving definitions of stone-free status. The objective of this study was to evaluate the effect of UAS size on stone-free rate (SFR), operative efficiency, and fragment clearance dynamics during f-URS for lower-pole stones using a 6 o'clock working-channel ureteroscope. This prospective multicenter pilot study included 49 patients undergoing f-URS across three tertiary referral centers. The primary outcome was strict SFR (0 mm), and secondary outcomes included clinical SFR (<2 mm), operative time, laser lithotripsy time, and fragment clearance patterns. Subgroup analysis focused on lower-pole stones. No statistically significant difference in strict SFR was observed between the 11/13 Fr and 12/14 Fr UAS groups. Clinical SFR also did not differ significantly between groups, although it was higher than strict SFR, particularly for lower-pole stones. Mean operative time was comparable between groups. Laser lithotripsy time was numerically longer in the 12/14 Fr group, but the difference was not statistically significant. Given the limited sample size, the findings should be considered exploratory and require confirmation in larger prospective studies. Trends in operative parameters and fragment clearance were observed and should be interpreted cautiously. Operative performance metrics and fragment clearance patterns may complement traditional binary stone-free outcomes when evaluating endourological innovations.