Treatment of anal fissure by lateral subcutaneous sphincterotomy should be under general anaesthesia.

Seventy-one consecutive patients with acute anal fissure were randomly allocated to treatment by lateral subcutaneous sphincterotomy under either local anaesthesia (n = 34) or general anaesthesia (n = 37). Four months after treatment there were 18 patients with a recurrent or persistent anal fissure, 17 had had local anaesthesia (50 per cent) and only one had a recurrent fissure after general anaesthesia (3 per cent). These results indicate that if lateral subcutaneous sphincterotomy is used for treatment of anal fissure the operation should be performed under a general anaesthetic.