Calculous anuria caused by obstructing upper ureteral stones in a solitary functioning kidney is a urological emergency requiring urgent decompression. Both retrograde JJ ureteral stenting and percutaneous nephrostomy are commonly used emergency drainage methods. However, limited evidence is available regarding whether the initial drainage method affects subsequent definitive flexible ureteroscopy/retrograde intrarenal surgery outcomes.

This multicenter prospective randomized controlled trial will compare emergency JJ ureteral stent drainage versus percutaneous nephrostomy drainage in adult patients presenting with calculous anuria due to a single upper ureteral stone in a solitary functioning kidney. After renal functional improvement, clinical stabilization, and appropriate urine culture management, all participants will undergo standardized definitive flexible ureteroscopy/retrograde intrarenal surgery. The study will assess renal functional recovery, first-session surgical success, stone-free rate, operative parameters, complications, and microbiological outcomes.

This is a multicenter prospective randomized controlled trial comparing two emergency drainage strategies before definitive flexible ureteroscopy/retrograde intrarenal surgery in patients presenting with calculous anuria.

Adult patients with calculous anuria caused by a single upper ureteral stone in a solitary functioning kidney will be assessed for eligibility. Eligible participants will be randomized in a 1:1 ratio to emergency retrograde JJ ureteral stent drainage or emergency percutaneous nephrostomy drainage. Randomization will be performed using a computer-generated random sequence, with allocation concealment using sequentially numbered opaque sealed envelopes.

Participants assigned to the JJ stent group will undergo emergency retrograde placement of a 6 Fr JJ ureteral stent under cystoscopic guidance. Participants assigned to the percutaneous nephrostomy group will undergo emergency ultrasound-guided placement of an 8 Fr nephrostomy tube. After drainage, participants will be monitored for urine output recovery, renal functional improvement, symptom relief, and clinical stabilization.

Definitive flexible ureteroscopy/retrograde intrarenal surgery will be scheduled after renal functional improvement, clinical stabilization, and negative or appropriately treated urine culture. The definitive procedure will be performed using a standardized operative strategy. Ureteral access sheath use, successful insertion, need for adjunctive ureteral maneuvers, operative time, laser time, fluoroscopy time, postoperative stenting, complications, and hospital stay will be recorded.

The primary outcome is renal functional recovery after initial drainage and definitive surgery, assessed using serial serum creatinine measurements at presentation, 24 to 48 hours after drainage, before definitive surgery, postoperative day 1, and follow-up. Secondary outcomes include first-session definitive surgery success, stone-free rate, technical operative variables, intraoperative and postoperative complications, microbiological culture patterns, and predictors of surgical success or postoperative complications.

Participants will be followed for approximately one month after definitive surgery by clinical assessment, laboratory evaluation, and imaging for assessment of renal function, complications, and stone clearance.

Inclusion Criteria:

• Adults aged 18 years or older.
• Calculous anuria secondary to a single upper ureteral stone.
• Solitary functioning kidney, whether anatomical or functional.
• Single upper ureteral stone confirmed by non-contrast computed tomography.
• Stone size from 6 mm to 20 mm in maximum diameter.
• Patient considered suitable for either initial JJ ureteral stent drainage or percutaneous nephrostomy drainage.
• Candidate for definitive treatment by flexible ureteroscopy/retrograde intrarenal surgery.
• Documented renal functional improvement and clinical stabilization before definitive RIRS.
• Negative or appropriately treated urine culture before definitive RIRS.
• Ability and willingness to provide written informed consent.

Exclusion Criteria:

• Multiple stones or bilateral stones not fitting the solitary-kidney study design.
• Renal pelvic, distal ureteral, or multiple ipsilateral stones.
• Stone burden greater than 20 mm.
• Septic shock, hemodynamic instability, or need for emergency dialysis at presentation.
• Pyonephrosis requiring a non-randomized drainage decision.
• Anatomical abnormalities affecting endoscopic access, such as horseshoe kidney, pelvic kidney, ureterocele, or ureteral stricture.
• Previous ipsilateral ureteral reconstructive surgery.
• Uncorrected coagulopathy.
• Pregnancy.
• Genitourinary malignancy.
• Inability to complete follow-up.

Individual participant data will not be shared because the study includes individual-level clinical, laboratory, radiological, operative, and microbiological data from patients presenting with an emergency urological condition. Only aggregated and de-identified study results will be reported. Any future sharing of individual participant data would require additional approval from the Research Ethics Committee and an appropriate data-sharing agreement.

Outcome assessors evaluating postoperative laboratory results, imaging-based stone-free status, complications, and microbiological outcomes will be blinded to the initial drainage allocation whenever feasible. Participants, care providers, and operating surgeons cannot be blinded because the assigned drainage method is clinically evident.