Intravesical Aminophylline to Facilitate Ureteroscopic Access in Children With Distal Ureteral Stones.

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

The study population will include children with symptomatic distal ureteral stones who are scheduled for definitive treatment by semi-rigid ureteroscopy. All eligible children will undergo standard preoperative evaluation, including history taking, clinical examination, laboratory investigations, urine culture, imaging assessment, and anesthetic assessment.

During surgery, after cystoscopy and guidewire placement when feasible, the surgeon will make one standardized gentle attempt to pass a small semi-rigid ureteroscope through the ureteric orifice and intramural ureter. No forceful advancement, balloon dilation, ureteric orifice incision, or repeated traumatic manipulation will be allowed during this initial attempt. Children in whom the ureteroscope passes successfully will continue standard ureteroscopic treatment and will be recorded in a screening log but will not be randomized.

Only children with failed initial gentle negotiation will be randomized intraoperatively in a 1:1 ratio to one of two groups. The aminophylline group will receive intravesical aminophylline at a dose of 0.5 mg/kg diluted in 0.9% normal saline to a fixed total volume of 50 mL. The placebo group will receive 50 mL of 0.9% normal saline. The solution will be instilled through a urethral catheter, the catheter will be clamped for approximately 5 minutes, the bladder will then be drained, and a second gentle ureteroscopic access attempt will be made.

The surgeon, anesthetist, patient, family, and postoperative outcome assessor will remain blinded to treatment allocation. The study solution will be prepared by a clinician or pharmacist who is not involved in surgery or postoperative assessment.

If ureteroscopic access becomes possible after instillation, definitive ureteroscopic stone treatment will continue in the same session. If access remains unsuccessful, the surgeon will follow the predefined rescue plan, which may include balloon dilation when judged safe, or JJ ureteral stenting with deferred ureteroscopy when dilation is unsafe, not feasible, or unsuccessful. Forceful ureteroscope advancement will not be allowed at any stage.

The primary outcome is successful passage of the intended semi-rigid ureteroscope through the ureteric orifice and intramural ureter after study instillation without balloon dilation. Secondary outcomes include the need for balloon dilation, the need for JJ stenting and deferred ureteroscopy, completion of definitive stone treatment in the same session, operative time, postoperative stenting, intraoperative ureteric injury, postoperative complications, stone-free status, need for auxiliary procedures, and early safety outcomes related to aminophylline.

Safety monitoring will include intraoperative and early postoperative cardiorespiratory monitoring. Heart rate and blood pressure will be recorded during the early peri-intervention period. Early serum theophylline levels will be measured in the first aminophylline-treated cases to document systemic exposure after local intravesical use. Any clinically significant unexpected adverse event, including arrhythmia, hemodynamic instability, seizure activity, or hypersensitivity, will be managed according to the study safety protocol.

Follow-up will include assessment in the immediate postoperative period, at 1 to 2 weeks, at approximately 4 weeks, and at approximately 3 months after surgery. Follow-up will assess postoperative recovery, pain, hematuria, fever or urinary tract infection, emergency visits or readmission, stent-related symptoms if a stent is inserted, stone-free status according to local imaging policy, delayed complications, and any need for secondary intervention.