Purpose: Lateral internal sphincterotomy has been the gold standard treatment for chronic anal fissure, but it still carries the risk of permanent damage of the anal sphincter, which has led to the implementation of alternative treatment like botulinum toxin injection. The aim of this randomized prospective controlled trial was to compare the efficacy and morbidity of botulinum toxin injection and lateral internal sphincterotomy in the treatment of chronic anal fissure.
Methods: Fifty consecutive adults with chronic anal fissure were randomly treated with either lateral internal sphincterotomy or botulinum toxin (BT) injection with 50 U BT into the internal sphincter. The complications, healing and recurrence rate, and incontinence score were assessed 2, 3, 6, 12 months after the procedure.
Results: Inspection at the 2-month visit revealed complete healing of the fissure in 11 (44 %) of the patients in the BT group and 22 (88 %) of the patients in the lateral internal sphincterotomy (LIS) group (p = 0.001). At the 3-month visit, there was no significant difference between the two groups in healing. The overall recurrence rate after 6 months in the BT group was higher than in the LIS group (p < 0.05). In the 3-month follow-up, the LIS group had a higher rate of anal incontinence compared to the BT group (p < 0.05). The final percentage of incontinence was 4 % in the LIS group (p > 0.05).
Conclusions: The treatment of chronic anal fissure must be individualized depending on the different clinical profiles of patients. Botulinum toxin injection has a higher recurrence rate than LIS, and LIS provides rapid and permanent recovery. However, LIS carries a higher risk of anal incontinence in patients.