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Background: Botulinum toxin injection into the internal anal sphincter (IAS) is gaining popularity as a second line therapy for chronic anal fissures after patients fail medical therapy. Although lateral internal sphincterotomy (LIS) can achieve a healing rate of 91-95%, it is associated with fecal incontinence of 11%. The dosage of Botulinum toxin reported in the literature ranged from 20-50 IU with no more than 3 injection sites and results in a healing rate of 65%-73% and recurrence rate of 35%. We propose a new injection method of high-dose circumferential chemodenervation (HDCC) of 100 IU in treating chronic anal fissure.
Aim: We evaluate the fissure healing, complication, and recurrence rates with this new method during 6 months study period after each injection.
Methods: Between 2008-2012, 75 consecutive patients (32 Blacks, 42 Whites, 1 Native American) (50 Women, 25 Men) with complete follow-up data were included in this study. These patients presented with uncomplicated chronic anal fissure and underwent HDCC-IAS by a single colorectal surgeon. HDCC is an anoscopy assisted percutaneous injection involving greater than 8 injection sites in a circumferential technique under anesthesia. Follow up data were obtained by chart review and office follow up.
Results: Of the 75 patients, the 1st injection success rate was 90.6% at 3 months follow-up (Table 1). A few patients developed transient flatus or fecal incontinence, but shortly resolved. There was no major complication following HDCC-IAS including hematoma, infection, flatus, fecal, and urinary incontinence after 1 month.
Conclusion: HDCC-IAS is a safe and effective method for uncomplicated chronic anal fissure. It's efficacy rivals reported LIS healing rate without the associated fecal incontinence. In addition, HDCC-IAS demonstrated far superior healing rates compared to standard injection method without increased complication rate.
Key Words: Botulinum toxin, anal fissure, injection, high-dose circumferential chemodenvervation (HDCC), internal anal sphincter, lateral internal sphincterotomy (LIS)
Table 1. Treatment of uncomplicated chronic anal fissures with high-dose circumferential chemodenervation (HDCC) of the internal anal sphincter

HDCC sessions	Healing Rate (3 months)	Healing Rate (6 months)	Recurrence Rate (6 months)	Average Healing Time (weeks)	Complications (after 1 month)
First injection (n=75)	90.6%	90.6%	8.0%	6.2	0
Second injection (n=16)	81.3%	93.8%	0%	7.4	0
3rd Injection (n=3)	100%	100%	33%	12	0
4th Injection (n=1)	100%	100%	100%	12	0
5th injection (n=1)	0%	100%	0%	20	0