A sphincterotomy is a procedure performed on the internal anal sphincter muscle for the treatment of chronic anal fissure.
The internal anal sphincter is one of two muscles that comprise the anal sphincter which controls the passage of faeces. The procedure is carried out whilst under sedation together with administration of local anaesthetic to the area being treated. The surgery involves making a very small incision between the internal sphincter and the external sphincter at the anal verge, and dividing the lowest fibres of the internal sphincter for a distance limited to the vertical height of the fissure, usually just a few millimetres (and always less than one centimetre), carefully preserving the majority of the internal sphincter and thus ensuring optimal control and continence. The technique helps to slightly lower the resting pressure of the internal anal sphincter, which improves blood supply to the fissure and allows faster healing.