High-dose circumferential chemodenervation of the internal anal sphincter: A new treatment modality for uncomplicated chronic anal fissure: A retrospective cohort study (with video).

[BACKGROUND] Botulinum toxin injection into the internal anal sphincter is gaining popularity as a second line therapy for chronic anal fissures if medical therapy fails. The dosage of botulinum toxin reported ranged from 20 to 50 IU with no more than 3 injection sites and results in a healing rate of 41%-88% at 3 months. We propose a new injection method of high-dose circumferential chemodenervation of 100 IU in treating chronic anal fissure.

[METHODS] This was a retrospective review at a single academic center. 75 patients (50 women and 25 men) with uncomplicated chronic anal fissures underwent high-dose circumferential chemodenervation-internal anal sphincter (100 IU). We measured fissure healing, complication, and recurrence rates at 3 and 6 months post injection.

[RESULTS] Of the 75 patients, healing rate was 90.7% at 3 months follow up with the first injection and 81.3% with the second injection. The recurrence rates were 20.6% and 12.5% at 6 months after the 1st and 2nd injections respectively. Excluding 5 patients who lost follow up, the total healing rate of the study cohort was 100%. At 2 weeks and 3 months, there were no major complications including hematoma, infection, flatus, fecal, and urinary incontinence.

[CONCLUSIONS] High-dose circumferential chemodenervation-internal anal sphincter (100 IU) is a safe and effective method for uncomplicated chronic anal fissure.