Internal Anal Sphincterotomy

An anal fissure is a common benign anorectal disease affecting both children and adults. It is a painful linear tear in the posterior anoderm extending the cephalad to the dentate line. Classically, these are caused by a large, firm, forceful bowel movement. This results in cycles of recurring anal pain and bleeding, leading to chronic anal fissures in as many as 40% of patients who develops fissures. An anal fissure can typically be diagnosed based on history alone. Patients describe moderate to severe anal pain with bowel movements with variable amounts of bleeding. The bleeding is described as blood on the toilet paper with wiping. The pain commonly persists for 15 to 30 minutes following a bowel movement. The exposed internal anal sphincter frequently spasms, leading to significant pain. If this persists, this muscle becomes hypertrophied leading to nonhealing anal fissures. Typically, these are self-limiting in children, whereas in adults, these can require surgical intervention.

The majority of anal fissures (90%) are located in the posterior midline. Fissures can be located in the anterior midline in as many as 25% of females and 8% of males. Fissures in the lateral position should raise concerns about other disease processes like inflammatory bowel disease or granulomatous diseases.

Several medical therapies, including salves, fiber, and topical nitroglycerin, aid in spontaneous closure early in the disease process. Surgical therapies include botulinum toxin injections, fissurectomy, advancement flaps, and internal lateral anal sphincterotomy. Surgical intervention is typically indicated with chronic fissures or for fissures that are not amenable to medical therapy.

Internal lateral anal sphincterotomy was first introduced in 1951 by Eisenhammer. The procedure provides prompt symptomatic relief by reducing pathologically elevated pressures within the anal canal. The procedure has provided a greater than 95% cure rate at 3 weeks post-procedure. Currently, it is considered the gold standard surgical intervention.