Efficacy and safety of botulinum toxin injection in the management of chronic symptomatic anal fissure: a systematic review and meta-analysis of randomized controlled trials

Background: Anal fissure is one of the most painful anal conditions. Various management options are available, including topical nitrites, calcium channel blockers, botulinum toxin injection, and lateral internal sphincterotomy. This study aimed to assess the efficacy and safety of botulinum toxin A (BT) injection for the management of symptomatic chronic anal fissures by conducting a systematic review of the literature and meta-analysis of published randomized controlled trials (RCTs).

Methods: A systematic search was conducted using the Embase and Medline search platforms. The search identified 264 papers published from January 1974 to December 2023, 35 of which were RCTs. Meta-analysis was performed on the collected data with a random effects model using Freeman-Tukey arcsine-transformed proportions. A p value less than 0.05 was considered to indicate statistical significance. The I² test was used to assess heterogeneity.

Results: A total of 1532 patients were included. After data were pooled, 1117 patients out of 1532 (72.7%) demonstrated healing of the fissure after the first injection of BT (P < 0.001, I² = 86.6%). Subgroup analysis was performed on the basis of the follow-up period in months. Nine studies reported that a second BT injection was needed for patients who did not respond after the initial injection. Twenty-nine out of 38 patients (78.5%) responded to the second injection (p < 0.001, I² = 50.6%). Complications were observed in 88 out of 1532 patients (4.02%) (p < 0.001, I² = 60.2%).

Conclusion: BT injection is a safe treatment approach for chronic symptomatic anal fissures, typically associated with only minor, temporary complications. Evidence also supports the use of repeat injections for managing recurrent or persistent symptoms.