Botulinum toxin A injection for chronic anal fissure: A retrospective observational study

Chronic anal fissure (CAF) is a common anorectal disorder associated with severe pain and impaired quality of life. Botulinum toxin A (BTA) injection has emerged as a minimally invasive alternative to lateral internal sphincterotomy; however, data regarding high-dose Dysport® protocols and the clinical relevance of booster injections remain limited. This retrospective single-center observational study was conducted at the General Surgery Clinic of Mersin City Training and Research Hospital. Patients treated for CAF between January 1, 2025, and December 1, 2025, were identified through institutional medical records. Sixty consecutive patients were screened; 10 were excluded because they did not attend follow-up visits, and 50 patients with complete follow-up data were included in the final analysis. All patients received a standardized 75 IU Dysport® injection targeting the internal anal sphincter. At the first follow-up reassessment, a booster injection was considered when either <50% reduction in visual analog scale (VAS) pain score or incomplete fissure healing was present. Pain severity was assessed using the VAS, and fissure healing was evaluated clinically and anoscopically. Outcomes were analyzed. The mean age was 45.8 ± 12.3 years, and 28 patients (56%) were men. The mean VAS pain score decreased from 7.80 ± 0.99 (95% confidence interval [CI]: 7.52-8.08) at baseline to 3.18 ± 0.85 (95% CI: 2.94-3.42) at 1 month and 1.00 ± 0.67 (95% CI: 0.81-1.19) at 3 months. Repeated-measures analysis of variance demonstrated a statistically significant reduction in pain over time (F[2, 98] = 1512.68, P < .001, partial η2 = 0.969). Healing was observed in 34/50 patients (68.0%, 95% CI: 54.2-79.2) at 1 month and 45/50 patients (90.0%, 95% CI: 78.6-95.7) at 3 months. Booster injections were required in 30/50 patients (60.0%, 95% CI: 46.2-72.4). Recurrence was observed in 5/50 patients (10.0%, 95% CI: 4.3-21.4) during follow-up; these patients subsequently underwent lateral internal sphincterotomy. Transient mild incontinence occurred in 3/50 patients (6.0%, 95% CI: 2.1-16.2) and resolved with conservative management. High-dose Dysport® injection appears to be a safe and effective minimally invasive option for the short-term treatment of CAF. A booster-based stepwise strategy may improve outcomes in selected patients before escalation to surgery.