Effect of Tidal Volume on fURS Parameters

The goal of this prospective clinical trial is to evaluate how intraoperative tidal volume settings affect surgical parameters and outcomes in adult patients undergoing flexible ureteroscopy (fURS) for kidney stones. The participant population includes patients over 18 years of age with unilateral, single renal stones located in the upper/middle calyx or renal pelvis. This study aims to answer are: Does intraoperative tidal volume influence operative time and surgical efficiency during fURS? Does tidal volume affect laser energy use, lasing efficiency, stone-free rates, and complication rates (infection or bleeding)? The investigators will compare two groups based on tidal volume recorded during anaesthesia: Group 1: Low tidal volume (\< 500 mL) Group 2: Standard tidal volume (≥ 500 mL) to determine whether tidal volume differences impact surgical performance and postoperative outcomes. Participants will: Undergo fURS performed under general anaesthesia with standard ASA monitoring, including ETCO₂ and TOF monitoring. Have their respiratory parameters (tidal volume, peak airway pressure, PEEP, respiratory rate, ETCO₂) and surgical data (operative time, laser settings, fluoroscopy use, stone-free status) recorded during and after surgery.