Role of Pre-stenting Before Retrograde Intrarenal Surgery With Miniaturized Flexible Ureteroscopes

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.