# Selective Omission of Ureteral Access Sheath in Retrograde Intrarenal Surgery: Surgical and Safety Outcomes from a Single-Center Retrospective Cohort Study

## TL;DR

This study shows that omitting a ureteral access sheath during kidney stone surgery can be as effective and safe as using it in specific cases.

## Contribution

The study introduces a selective strategy for omitting the ureteral access sheath in RIRS based on stone size and technical difficulty.

## Key findings

- Sheathless RIRS had similar stone-free rates and operative times compared to UAS-assisted RIRS.
- No febrile infections or sepsis occurred in the sheathless group, unlike the UAS group.
- Lower calyceal stone location was the only factor independently associated with stone-free rates.

## Abstract

Introduction: The ureteral access sheath (UAS) is commonly used in retrograde intrarenal surgery (RIRS) to improve vision, lower intrarenal pressure (IRP), and facilitate access. However, concerns regarding ureteral injury remain. We conducted this study to evaluate the surgical efficacy and safety of a selective omission strategy for UAS use during RIRS in patients with small renal stones (<10 mm) or in cases where UAS placement is technically difficult. Materials and Methods: This retrospective study included consecutive patients who underwent single-surgeon RIRS at Changhua Christian Hospital between October 2020 and April 2023 for renal or upper ureteral stones. Sheathless RIRS was performed in patients with stones < 10 mm, or in whom insertion of a 10/12 Fr UAS was unsuccessful despite successful advancement of an 8 Fr semirigid ureteroscope, and when the surgeon estimated the procedure could be completed within 2 h. All procedures used a holmium laser with a 9 Fr or 7.5 Fr flexible ureteroscope. No patients were pre-stented, and all received postoperative double-J stenting. Results: Among 55 patients, 18 (32.7%) underwent sheathless RIRS and 37 (67.3%) underwent UAS-assisted RIRS. Stone size was significantly smaller in the sheathless group (12 mm vs. 17 mm, p = 0.001). The 3-month stone-free rate (SFR) was 66.7% in the sheathless group and 62.2% in the UAS group (p = 0.745). Operative time was similar between groups (77 vs. 85 min, p = 0.154), with no statistically significant differences in postoperative pain or length of hospital stay. In the UAS-assisted group, six patients developed febrile urinary tract infection, of whom two progressed to sepsis; all recovered after antibiotic therapy. No fever or sepsis occurred in the sheathless group. On multivariable analysis, lower calyceal stone location was independently associated with SFR, whereas UAS use was not. Conclusions: In a selected cohort (stones < 10 mm or difficult UAS insertion with an expected operative time < 2 h), sheathless RIRS was feasible and showed no statistically significant differences in SFR or perioperative outcomes compared with UAS-assisted RIRS. However, due to selection bias, stone-size imbalance, and limited statistical power, these findings should not be interpreted as procedural equivalence and require confirmation in adequately powered studies with stratified/adjusted analyses.