Pre-stenting in Miniaturized RIRS

Retrograde intrarenal surgery is widely used for the treatment of selected renal calculi. Miniaturized flexible ureteroscopes may facilitate direct ureteral and renal access, potentially reducing the need for routine preoperative ureteral stenting. However, pre-stenting may improve passive ureteral dilation, facilitate access, reduce failed access, and decrease the need for staged treatment.

Participants will be randomly assigned in a 1:1 ratio to either preoperative double-J ureteral stenting for 7-14 days followed by RIRS or direct RIRS without planned preoperative ureteral stenting. All procedures will use a standardized miniaturized digital flexible ureteroscope and holmium:YAG laser lithotripsy technique. If safe access cannot be obtained in the direct-RIRS group, rescue ureteral stenting will be performed, and definitive RIRS will be delayed for approximately 7-14 days.

The primary outcome will be the stone-free rate assessed by non-contrast computed tomography 4 weeks after the final RIRS procedure. Secondary outcomes will include successful ureteroscopic access, need for active dilation, procedure abandonment, staged RIRS, operative time, laser parameters, ureteral injury, postoperative complications, hospital stay, pain, stent-related symptoms, readmission, and auxiliary procedures.

Inclusion criteria

• Participants must meet all of the following criteria:

• Adults aged 18-70 years.
• Unilateral renal calculi.
• Maximum total renal stone burden of 10-20 mm.
• Planned treatment with RIRS.
• Suitable candidate for elective endoscopic stone treatment.
• Negative or appropriately treated preoperative urine culture.
• Ability to provide written informed consent.
• Ability and willingness to comply with postoperative follow-up, including non-contrast CT at 4 weeks after the final RIRS procedure.

Exclusion criteria

• Participants will be excluded for any of the following:

• Bilateral renal calculi requiring simultaneous surgical treatment.
• Active urinary tract infection, sepsis, or infected obstruction requiring urgent drainage.
• Solitary kidney when randomization is considered clinically unsafe.
• Known ureteral stricture or congenital ureteral abnormality likely to interfere with ureteroscopic access.
• Previous failed ipsilateral ureteroscopic access requiring clinically indicated pre-stenting.
• Existing ipsilateral ureteral stent or nephrostomy.
• Previous ureteral reconstruction or urinary diversion.
• Total renal stone burden greater than 20 mm.
• Staghorn calculi.
• Uncorrected coagulopathy.
• Pregnancy.
• Severe uncorrected cardiopulmonary disease precluding anesthesia.
• Inability or unwillingness to provide informed consent.
• Inability or unwillingness to comply with follow-up.
• Any other condition judged by the treating surgeon to make randomization or RIRS clinically inappropriate or unsafe.