Comparison of Flexible-Tip and Non-Flexible Ureteral Access Sheaths for Treatment of Renal Lower Calyx Stones

INTRODUCTION: The aim of the study was to compare the efficacy of a flexible-tip ureteral access sheath (F-UAS) with a traditional non-flexible ureteral access sheath (T-UAS) in the treatment of renal lower calyx stones. METHODS: This retrospective analysis included clinical data from patients with unilateral renal lower calyx stones who underwent treatment with either an F-UAS (cases from December 2023 to September 2024) or a T-UAS (cases from January 2023 to November 2023). Inclusion criteria were ages 18-75 years, lower pole kidney stones measuring 1-2 cm. The primary outcome was the immediate postoperative stone-free rate (SFR) on the first day post-surgery. Secondary outcomes included operative time, postoperative complications, postoperative hospital stay, and 3-month SFR. RESULTS: A total of 132 patients were included in the study, with 63 in the F-UAS group and 69 in the T-UAS group. Baseline characteristics were comparable between groups. The F-UAS group demonstrated a significantly higher day-1 postoperative SFR (73.0% vs. 17.4%; p < 0.001). The overall complication rate was lower in the F-UAS group (p = 0.031), with a notably reduced incidence of postoperative fever. The F-UAS group also had a significantly lower basket usage rate (20.6% vs. 100%; p < 0.001). There were no significant differences in operative time or 3-month SFR between the groups (p = 0.097 and p = 0.354, respectively). Hospital stay and stone composition were also similar between groups. CONCLUSION: Compared to T-UAS, the use of F-UAS for retrograde intrarenal surgery in the treatment of renal lower calyx stones is associated with a higher day-1 SFR. Additionally, the F-UAS group demonstrated reduced basket usage and fewer postoperative complications.