Acute calculous anuria is a urological emergency caused by ureteral stone obstruction in a solitary functioning kidney or bilateral ureteral obstruction. Urgent decompression of the upper urinary tract is required to restore urine drainage and prevent further renal impairment.

This prospective randomized double-blind controlled trial will evaluate whether intravesical aminophylline can facilitate urgent retrograde ureteral stenting in adult patients with acute calculous anuria due to ureteral stones. Eligible patients will be randomly assigned to receive either intravesical aminophylline diluted in normal saline or placebo saline before attempted retrograde Double-J ureteral stent placement.

The primary outcome is technical success, defined as successful placement of a Double-J ureteral stent across the obstructing stone without the need for percutaneous nephrostomy. Secondary outcomes include stenting time, intraoperative complications, renal function recovery, postoperative pain, analgesic requirement, and the need for alternative drainage.

This is a prospective, randomized, double-blind, controlled trial conducted at the Department of Urology, Beni-Suef University Hospital.

The study will include adult patients aged 18 years or older presenting with acute calculous anuria due to ureteral stone obstruction in a solitary functioning kidney or bilateral ureteral obstruction. Obstruction will be confirmed by pelvi-abdominal ultrasound and computed tomography of the urinary tract. Eligible patients will have clinical and laboratory evidence of acute renal impairment, including oliguria or anuria and elevated serum creatinine.

After eligibility assessment and informed consent, participants will be randomly allocated in a 1:1 ratio to one of two groups.

Participants in the aminophylline group will receive intravesical instillation of 250 mg aminophylline diluted in normal saline to a total volume of 160 mL. Participants in the control group will receive placebo intravesical instillation using normal saline with the same total volume. The study solution will be prepared by a nurse who is not involved in the operation to maintain blinding of the patient and the operating surgeon.

Under general or spinal anesthesia, the patient will be placed in the lithotomy position. A cystoscope will be introduced and the bladder will be emptied. The assigned intravesical solution will then be instilled into the bladder and retained for 5 minutes before proceeding with retrograde ureteral stenting. Under fluoroscopic guidance, a guidewire will be advanced through the ureteric orifice in an attempt to bypass the obstructing ureteral stone. If successful, a Double-J ureteral stent will be advanced over the guidewire and positioned across the obstruction.

The primary endpoint is technical success of retrograde ureteral stenting, defined as successful placement of the Double-J stent across the obstructing stone without the need for percutaneous nephrostomy. Secondary endpoints include time required for successful stent placement, intraoperative complications, serum creatinine changes at 24, 48, and 72 hours after decompression, postoperative pain score, analgesic requirement, and the need for alternative drainage after failed retrograde stenting.

Inclusion Criteria:

1. Patients aged 18 years or older.
2. Diagnosis of acute calculous anuria due to ureteral stone obstruction in a solitary functioning kidney.
3. Obstruction confirmed by pelvi-abdominal ultrasound and computed tomography of the urinary tract.
4. Clinical and laboratory evidence of acute renal impairment, including oliguria or anuria and serum creatinine >2 mg/dL.
5. Ability to provide written informed consent.

Exclusion Criteria:

1. Known hypersensitivity to aminophylline, theophylline, or other methylxanthines.
2. Evidence of active urinary tract infection or urosepsis.
3. Previous history of ureteral stricture or major urinary tract reconstructive surgery.
4. Hemodynamic instability requiring immediate life-saving measures before urological intervention.
5. Pregnancy.

Individual participant data will not be shared. Only aggregated, de-identified study results will be reported. Individual-level data will remain confidential and will be accessible only to the study investigators and authorized regulatory or ethics committee representatives if required.

The intravesical study solution will be prepared by a nurse not involved in the procedure. Participants, care providers, investigators, and outcome assessors will be blinded to group allocation.