Effect of intrasphincteric botulinum toxin on postoperative urinary retention following stapled hemorrhoidopexy: a randomized, double-blind, placebo-controlled trial

Postoperative urinary retention (POUR) is a frequent and clinically significant complication following stapled hemorrhoidopexy, often resulting in catheterization, prolonged hospitalization, and patient discomfort. Strategies to reduce POUR remain limited. Intrasphincteric botulinum toxin (BTX) injection may decrease internal anal sphincter tone and indirectly reduce urinary dysfunction. To evaluate the effect of intrasphincteric BTX type A injection on the incidence of POUR following stapled hemorrhoidopexy in a secondary analysis of a prospective randomized controlled trial originally designed to assess postoperative pain outcomes. In this double-blind, placebo-controlled trial, 68 adult patients with grade III-IV hemorrhoids undergoing stapled hemorrhoidopexy at two tertiary hospitals were randomized (1:1) to receive either 50 units of BTX A or placebo injected into the internal anal sphincter intraoperatively. The primary outcome was POUR, defined as failure to void within six hours postoperatively with a bladder volume > 400 mL on ultrasound requiring catheterization. Secondary outcomes included postoperative pain, gas incontinence, bleeding, and anal stenosis. POUR occurred in 30 patients (44.1%). The incidence was significantly lower in the BTX group compared with placebo (20.6% vs. 67.6%, P < 0.001). In multivariable logistic regression adjusted for age and sex, placebo treatment was independently associated with higher odds of POUR (adjusted OR 8.87, 95% CI 2.82-27.95; P < 0.001). No significant differences were observed in postoperative bleeding or gas incontinence. Intrasphincteric BTX injection significantly reduces postoperative urinary retention following stapled hemorrhoidopexy and may represent an effective perioperative strategy to improve surgical.Registration: IRCT20130826014483N12; Registered 25 June 2025 (Retrospectively registered).