BACKGROUND—Chronic anal fissure is a common and painful condition associated with internal anal sphincter hypertonia. Reduction of this hypertonia improves the local blood supply, encouraging fissure healing. Surgical sphincterotomy is very successful at healing these fissures but requires an operation with associated morbidity. Temporary reduction in sphincter tone can be achieved on an outpatient basis by applying a topical nitric oxide donor (for example, glyceryl trinitrate) or injecting botulinum toxin into the anal sphincter. METHODS—A Medline database was used to perform a literature search for articles relating to the non-surgical treatment of chronic anal fissure. RESULTS—Review of the literature shows botulinum toxin injection to be more effective at healing chronic anal fissures than topical glyceryl trinitrate. Topical isosorbide dinitrate has not been directly compared with either of these two agents but has a healing rate approaching that of botulinum toxin injection. The main side effect of botulinum toxin injection is temporary faecal incontinence in approximately 2% of cases, whereas topical nitrates cause headaches in 20%-100% of cases. No long term side effects were identified with any of the medical treatments. CONCLUSION—Chemical sphincterotomy is an effective treatment for chronic anal fissure and has the advantages over surgical treatment of avoiding long term complications (notably incontinence) and not requiring hospitalisation.
