Background <p>Impacted upper ureteral stones pose a significant risk of ureteral injury and stricture formation during ureteroscopic procedures. The Flexible and Navigable Suction Ureteral Access Sheath (FANS) integrates in-situ lithotripsy, continuous suction, and irrigation. This study aimed to compare the efficacy and safety of FANS with the conventional ureteroscopic technique in the management of impacted upper ureteral stones.</p> Methods <p>A single-center, retrospective cohort study was conducted involving 115 patients (FANS group: <i>n</i> = 50; Conventional group: <i>n</i> = 65). The FANS group underwent in-situ holmium laser lithotripsy with real-time irrigation and suction facilitated by FANS. The Conventional group underwent in-situ lithotripsy using a semi-rigid ureteroscope, with subsequent attempts to push stones into the renal pelvis before flexible ureteroscopic fragment extraction. The rates of ureteral stricture (within 3 months) and other perioperative parameters, including operative time, in-situ lithotripsy duration, and complications, were compared.</p> Results <p>Baseline characteristics were comparable between the two groups. The FANS group exhibited significantly longer operative and in-situ lithotripsy times. However, the incidence of ureteral stricture and perforation was lower in the FANS group (2% vs. 7.7% and 2% vs. 6.2%, respectively). Subgroup analyses revealed that prolonged in-situ lithotripsy time was a significant risk factor for ureteral stricture in the control group but not in the FANS group. The immediate stone-free rate was comparable between groups, with a lower rate of postoperative fever in the FANS group.</p> Conclusion <p>For impacted upper ureteral stones, FANS assisted in-situ lithotripsy significantly reduces the risk of postoperative ureteral stricture without compromising stone clearance, offering a safer alternative to the conventional stone-pushing technique.</p>