A Novel ±20° Gravity-Assisted Position for Tip-Bendable Suction Ureteral Access Sheath in Retrograde Intrarenal Surgery: A Multicenter Retrospective Study on Large Stone Management

<b><i>Purpose:</i></b> To evaluate the efficacy of combining a tip-bendable suction ureteral access sheath (S-UAS) with gravity-assisted positioning to improve stone-free rates (SFRs) in retrograde intrarenal surgery (RIRS) for upper urinary tract stones (UUTS). <b><i>Methods:</i></b> A multicenter retrospective cohort study was conducted across three urological centers from July 2023 to August 2024. A total of 369 patients with UUTS treated with RIRS using S-UAS were included. Patients were categorized into two groups based on surgical positioning: the ±20° gravity-assisted position group and the standard lithotomy group. SFRs were classified into three grades: Grade A (no residual fragments on CT), Grade B (≤2mm fragments), and Grade C (≤4mm fragments). Key outcomes measured included immediate and 3-month SFR, operative time, and complication rates. Logistic regression analysis was used to identify factors associated with improved SFR. <b><i>Results:</i></b> The ±20° gravity-assisted position group showed a significantly higher immediate Grade-A (71.3% <i>vs</i> 48.1%, <i>p</i> < 0.001) and Grade-B SFR (86.0% <i>vs</i> 67.2%, <i>p</i> < 0.001) compared to the standard lithotomy group. This superiority in Grade-A SFR persisted at 3 months (76.0% <i>vs</i> 49.6%, <i>p</i> < 0.001). The median operative time was shorter in the ±20° gravity-assisted position group (67 <i>vs</i> 71 minutes, <i>p</i> = 0.0032) and the frequency of stone basket use was lower in ±20° gravity-assisted position. Multivariate analysis revealed that the lithotomy position was independently associated with a lower stone-free probability (adjusted odds ratio 0.36, 95% confidence interval 0.17-0.80; <i>p</i> = 0.012). No significant differences were observed in complication rates between the two groups. <b><i>Conclusion:</i></b> The ±20° gravity-assisted position improves immediate SFR in RIRS for UUTS, with shorter operative times. Combining gravity-assisted positioning with S-UAS is an effective strategy to optimize surgical outcomes in RIRS.