Comparison of botulinum toxin injection and lateral internal sphincterotomy for the treatment of chronic anal fissure

Abstract

Purpose: Botulinum toxin injection into the internal anal sphincter has been shown to be an effective treatment for chronic anal fissure. A randomized, prospective trial was conducted to compare botulinum toxin with lateral internal anal sphincterotomy as definitive management for chronic anal fissure.

Methods: Patients diagnosed as having chronic anal fissure were randomly assigned to one of the two treatment arms. In the botulinum toxin group (n = 61), 20 to 30 U (approximately 0.3 U/kg) of type A botulinum toxin (Botox) was injected into the internal anal sphincter. The injection was repeated two months later if complete healing was not accomplished. Patients in the sphincterotomy group (n = 50) underwent lateral internal anal sphincterotomy. The same investigators evaluated the patients on postoperative/postinjection days 7 and 28, and then in a blinded manner at 2, 6, and 12 months.

Results: In the botulinum group, single injection resulted in complete healing in 45 of the 61 patients (73.8 percent) at the second month. Of the 16 failures, 6 patients refused further treatment, and 10 were treated with a second injection, which resulted in an overall healing rate of 86.9 percent (53/61) at 6 months. In the sphincterotomy group, the success rate was 82 percent (41/50) at day 28 and 98 percent (49/50) at the second month (P = 0.023 and P < 0.0001, respectively, compared with the botulinum group-single injection). At 6 months, 2 patients in the LIS group developed recurrences, and the healing rate was similar to that of the botulinum group (86.9 96.4 percent; P = 0.212). At 12 months, the success rate of the Botox group fell to 75.4 percent (46/61) with 7 recurrences, whereas it remained stable in the sphincterotomy group (94 percent, P = 0.008). Sphincterotomy was associated with a significantly higher complication rate (8 cases of anal incontinence none in the botulinum toxin group; P < 0.001). Full return to daily activities took significantly less time in the botulinum group (1 14.8 +/- 5.7 days; P < 0.0001).

Conclusion: Although the healing rate of chronic anal fissure is considerably high with botulinum toxin injection with earlier recovery and less complications compared with sphincterotomy, it occasionally requires a repeat injection, and the healing is slower. The early (two months) and late (one year) healing rates are significantly higher in the sphincterotomy group, the two groups reaching similar healing rates only at six months.