Under general anesthesia, a 6 Fr ureteral catheter will be placed into the target ureter via cystoscopy, and bladder drainage will be achieved with a 16 Fr Foley catheter. The patient will then be repositioned to the prone position. Percutaneous renal access will be obtained by puncturing the selected calyx with an 18-gauge coaxial needle under fluoroscopic or ultrasound guidance. Tract dilation will be performed using fascial dilators up to 20 Fr then the mini-PCNL sheath (mini-Amplatz sheath) will be inserted and the mini nephroscope 12 to 15 Fr will be used. If multiple nephrostomy tracts are required for stone removal, the same approach will be repeated for each tract. Stone fragmentation will be carried out with a pneumatic lithotripter.

At the end of the procedure, a 6 Fr double-J ureteral stent will be inserted for 4 weeks, and whether to place a nephrostomy tube will be determined at the discretion of the operating surgeon.

under general anesthesia with the patient in the lithotomy position. A 6 Fr ureteral catheter will first be placed into the ureter, followed by retrograde pyelography to assess the upper urinary tract. A guidewire will then be advanced into the renal pelvis. either a 12/14 Fr or 11/13 Fr tip-bendable S-UAS will be inserted. If insertion is not possible due to ureteral narrowing, a smaller 10/12 Fr UAS will be attempted. if failed, a double-J stent will be placed and the procedure terminated, with a second session scheduled 4 weeks later. fURS will be performed using digital flexible ureteroscopes either 8.5 Fr or 7.5 Fr according to UAS size; an 8.5-Fr scope for a 12/14 Fr UAS, and a 7.5-Fr scope for an 11/13-Fr or 10/12-Fr UAS. Stone fragmentation will be performed using a holmium laser (Ho: YAG) with a 272-μm fiber and an energy setting below 30 W. Irrigation will be maintained at 50-100 ml/min and suction pressure at 80-120 mmHg. at the end a 6 Fr JJ will be inserted for 4 weeks.

Under general anesthesia, a 6 Fr ureteral catheter will be placed into the target ureter via cystoscopy, and bladder drainage will be achieved with a 16 Fr Foley catheter. The patient will then be repositioned to the prone position. Percutaneous renal access will be obtained by puncturing the selected calyx with an 18-gauge coaxial needle under fluoroscopic or ultrasound guidance. Tract dilation will be performed using fascial dilators up to 20 Fr then the mini-PCNL sheath (mini-Amplatz sheath) will be inserted and the mini nephroscope 12 to 15 Fr will be used. If multiple nephrostomy tracts are required for stone removal, the same approach will be repeated for each tract. Stone fragmentation will be carried out with a pneumatic lithotripter.

At the end of the procedure, a 6 Fr double-J ureteral stent will be inserted for 4 weeks, and whether to place a nephrostomy tube will be determined at the discretion of the operating surgeon.

The proportion of participants in each treatment arm who are completely free of any stone fragments in the treated kidney, following the initial procedure and without the need for any secondary surgical interventions. Status will be determined by a blinded central radiologist.

The total duration of inpatient hospitalization following the procedure, calculated from the day of surgery to the day of discharge