Patients in this group will undergo retrograde intrarenal surgery (RIRS) using the intrarenal pressure (IRP)-monitoring flexible and navigable suction ureteral access sheath (FANS). This novel device provides real-time IRP monitoring, enabling the surgeon to adjust intraoperative irrigation and suction settings to optimize stone retrieval efficiency while maintaining IRP within a safe range.

Patients in this group will undergo RIRS using a conventional flexible and navigable suction ureteral access sheath (FANS) without intrarenal pressure (IRP) monitoring. The irrigation flow rate and suction pressure will be pre-set and adjusted based on standard clinical practices.

The IRP-Monitoring Flexible and Navigable Suction Ureteral Access Sheath (FANS) is a novel device designed to enable real-time monitoring of intrarenal pressure (IRP) during retrograde intrarenal surgery (RIRS). It incorporates a pressure-sensing port connected to a gas conduit embedded in the sheath, which allows the surgeon to adjust irrigation flow and suction pressure based on real-time IRP readings, thereby optimizing stone retrieval efficiency while ensuring safety by maintaining a safe IRP range. The device improves surgical outcomes, particularly in complex cases involving larger renal stones, by reducing operative time and minimizing the risk of complications.

The primary outcome will be the total operative time, measured from the insertion of the endoscope into the urethra to the completion of stent placement. This outcome will assess the efficiency of stone retrieval when using either the IRP-monitoring FANS or the conventional FANS.

The stone-free rate (SFR) will be measured postoperatively through non-contrast CT imaging. The SFR will assess the effectiveness of stone retrieval and the success of the procedure.