Long-term Safety of UAS-assisted vs Sheathless RIRS in Non-prestented Patients

Inclusion Criteria: * Age ≥18 years at time of index RIRS. * Primary RIRS performed at Al-Azhar University Hospitals between Jan 1, 2020 and Dec 31, 2025. * Renal stone(s) with maximum diameter ≤20 mm on preoperative imaging. * No ipsilateral ureteral stent or nephrostomy before index RIRS. * Documented operative record specifying whether a UAS was used. * At least 12 months elapsed since index RIRS. * Available contact information allowing invitation for active follow-up. Exclusion Criteria: * Primary ureteral stone treated during the same procedure. * Staghorn or \>20 mm stone burden. * Prior ipsilateral ureteral stricture or reconstructive surgery. * Congenital renal/ureteral anomalies affecting outcome (e.g., horseshoe kidney, duplicated system). * Incomplete operative or preoperative imaging records that preclude determination of eligibility or exposure (UAS use). * Additional ipsilateral ureteral procedure during follow-up that independently causes ureteral narrowing. * Refusal to participate in active follow-up or failure to attend after repeated attempts.