Anal Fissures: Internal Anal Sphincterotomy

Topic Overview

Surgery may be needed if medicine fails to heal a tear (fissure) in the anus. The preferred procedure is an internal anal sphincterotomy. A doctor makes a small incision in the internal anal sphincter, one of two muscles that control the anus. This can be done as outpatient surgery under local anesthesia or general anesthesia.

The internal anal sphincter is always under tension, also known as resting pressure. If that pressure becomes too high, a fissure may form or an existing one may not heal. The incision reduces the resting pressure, allowing the fissure to heal.

It's important to understand that, even with surgery, an anal fissure must heal on its own. A sphincterotomy involves operating on the sphincter muscles, not closing the actual fissure.

Internal anal sphincterotomy has a better success rate than any medicine that is used to treat long-term anal fissures. The results last longer, and fewer people have anal fissures come back after surgery than after treatment with medicine.^{footnote 1}

In some studies, a greater number of people who had internal anal sphincterotomy had some inability to control gas or stool (incontinence) after surgery compared to people treated with medicine. Despite these results, satisfaction with this surgery is high. And a review of many studies showed that the risk of incontinence was 8%. This means that about 8 out of 100 people who had the surgery had some problem with incontinence. But this rate was not very different from the rates seen in people who were treated with medicine for their chronic anal fissures.^{footnote 2}

Another study showed that internal anal sphincterotomy was better than nitroglycerin cream at healing chronic anal fissures. And there was no difference in long-term continence between the people who used nitroglycerin cream and the people who had surgery.^{footnote 3}

If you are deciding whether to have this surgery, it is important that you consider the chance of incontinence. In some cases, the risk of incontinence is too great to justify doing internal anal sphincterotomy. This may be true for women who develop a fissure while giving birth, because they typically don't have a high resting pressure in their internal sphincter. A procedure called anal advancement flap may be done instead of sphincterotomy. In this procedure, the edges of the fissure are removed, and healthy tissue is sewn over the area.