Comparative Efficacy of Tamsulosin, Intraureteral Aminophylline, and Their Combination in Facilitating Ureteral Access During Retrograde Intrarenal Surgery: A Multicenter Randomized Controlled Trial.

Retrograde intrarenal surgery is a commonly used minimally invasive procedure for the treatment of renal stones. Successful completion of the procedure may require placement of a ureteral access sheath. However, ureteral access sheath insertion can be difficult in some patients because of ureteral resistance or spasm, which may lead to ureteral trauma, active ureteral dilatation, prestenting with delayed surgery, or inability to complete the planned procedure.

This study is designed to compare systemic, local, and combined pharmacologic strategies for facilitating ureteral access during primary retrograde intrarenal surgery. Tamsulosin is an alpha-1 adrenergic receptor blocker that may reduce ureteral tone when given before surgery. Aminophylline is a smooth-muscle relaxant that may reduce ureteral spasm when administered locally into the ureter during the procedure.

This is a prospective, multicenter, randomized, double-blind, placebo-controlled, parallel-group trial with a 2x2 factorial design. Eligible adult patients with unilateral renal stones measuring 2 cm or less who are scheduled for primary retrograde intrarenal surgery with planned 10/12 Fr ureteral access sheath placement will be randomized in a 1:1:1:1 ratio. The four treatment combinations are: placebo capsule plus intraureteral placebo, tamsulosin capsule plus intraureteral placebo, placebo capsule plus intraureteral aminophylline, and tamsulosin capsule plus intraureteral aminophylline.

Patients assigned to tamsulosin will receive tamsulosin 0.4 mg once daily for 7 days before surgery, while patients assigned to placebo will receive a matching placebo capsule. During surgery, the assigned intraureteral solution will be instilled through an open-end ureteric catheter positioned in the distal ureter on the study side. After a standardized 5-minute waiting period, one controlled attempt will be made to place the planned 10/12 Fr ureteral access sheath.

The primary endpoint is successful first-attempt placement of the planned 10/12 Fr ureteral access sheath after study solution instillation, without active ureteral dilatation, sheath downsizing, prestenting with deferred retrograde intrarenal surgery, or abandonment of the procedure due to access failure. If the planned sheath cannot be inserted safely, management will proceed according to a predefined rescue pathway, including active ureteral dilatation if considered safe or ureteral stenting with deferred surgery. Forced sheath advancement against marked resistance will be avoided.