Outcomes Following Intrasphincteric Injection of Botulinum Toxin for Treatment of Anal Fissures

Background Intrasphincteric injection of botulinum toxin is an alternative treatment for anal fissures, which may present less risk of fecal incontinence than more invasive procedures, such as lateral internal sphincterotomy. The aim is to compare cure and complication rates between these two treatments. Methods We conducted a retrospective audit of patients who underwent treatment of anal fissures with intrasphincteric botulinum toxin or lateral internal sphincterotomy from 2016 to 2020 at the Colorectal Surgery Unit of Monash Health, Melbourne, Australia, excluding those who had previously had either procedure. Results Fifty-one patients received intrasphincteric botulinum toxin, and 40 patients underwent lateral internal sphincterotomy. Most patients in the botulinum group had a total dose of either 80 (53%; n=27) or 100 units (37%; n=19) and had the dose administered bilaterally at the 3 o'clock and 9 o'clock positions (n=41; 80%). Thirty-one patients in the botulinum group (61%) had complete resolution of symptoms, with a mean time to cure of two months, compared to 36 patients (90%) in the sphincterotomy group with a mean time to cure of 1.5 months. In most cases, postoperative incontinence was transient, although one patient in the botulinum group had persistent incontinence of flatus, and two patients in the sphincterotomy group had persistent fecal incontinence. Conclusion Intrasphincteric botulinum injection is an effective, less-invasive alternative to sphincterotomy for the treatment of anal fissures, with incontinence usually temporary when it occurs. Further research is needed to optimize the dose and location of injection and guide future recommendations.