OPTIMAL DOSING AND INJECTION LOCATION OF BOTULINUM TOXIN FOR SUSTAINED HEALING OF CHRONIC ANAL FISSURE: A SYSTEMATIC REVIEW AND META-ANALYSIS melanie.m.flaherty@gmail.com

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OPTIMAL DOSING AND INJECTION LOCATION OF BOTULINUM TOXIN FOR SUSTAINED HEALING OF CHRONIC ANAL FISSURE: A SYSTEMATIC REVIEW AND META-ANALYSIS

3

New Zealand

Oral or Poster

Chronic anal fissures (CAF) are associated with significant morbidity and reduction in quality of life. Botulinum toxin (BT) is an established treatment for CAF but there is no consensus for the optimal dosage or injection location for sustained healing of the fissure.

A systematic review was conducted according to PRISMA guidelines using the Medline, EMBASE, and CENTRAL databases (PROSPERO CRD42025625589). Randomized controlled trials (RCTs) with documented follow-up until at least 24 weeks without any confounding anal pathologies were included. The primary outcome was healing of the CAF at >24 weeks of follow-up with recurrences classified as treatment failures. Secondary outcomes were adverse effects of incontinence. Risk of bias was assessed using the ROB2 tool.

Eighteen RCTs were included for analysis with 758 participants (49% F) with a mean age of 41.4 years. All received BT injections into the internal anal sphincter (IAS). Mean follow-up post-treatment was 92.6 weeks. 50-100U of BT injected into the midline had the highest healing rate at 87% (p < 0.001) but carried the highest incontinence rate (18%). Injections of 20-49U of BT into the lateral or midline aspect of the IAS produced similar rates of healing (68%, 63%) and incontinence rates (5%, 6.9%).

Injections of 20-49U of BT into either the midline or lateral aspect of the IAS produce sustained healing of CAF in > 60% of patients with minimal incontinence rates. Higher doses are associated with healing only if injected into the midline and carry a substantial incontinence risk.