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What Is a Lateral Internal Sphincterotomy?

By H. Colledge
Updated Mar 03, 2024
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Lateral internal sphincterotomy is a type of surgery used to treat a condition known as chronic anal fissure. An anal fissure occurs when the skin lining the anal passage tears, causing severe pain and sometimes bleeding when passing stools. In some people, healing is prevented because the valve, or sphincter, at the anal opening goes into spasm, reducing the blood supply to the damaged area. When non-surgical treatments have failed, lateral internal sphincterotomy may be recommended. During the procedure the sphincter muscle is cut to relieve spasming and enable healing to occur

An anal fissure can cause a lot of pain, often resulting in constipation as patients become reluctant to pass stools. Bleeding is typically seen on toilet paper after a bowel movement, and the blood is bright red in color. Many anal fissures are thought to be caused by passing a hard stool, and often they will heal by themselves. In people where healing does not take place it is thought that an abnormality of the internal anal sphincter may be present, which reduces the amount of blood flowing to the fissure area. The sphincter muscle pressure is often too high, and lateral internal sphincterotomy can lower the pressure to a normal level.

For most patients, medical anal fissure treatment is successful by using measures such as stool softeners and high-fiber diets. It is when such treatments fail that patients may undergo a lateral internal sphincterotomy procedure. Surgery can be carried out under a general anesthetic, so patients are unconscious, or a spinal anesthetic, where they are sedated but awake.

The surgeon uses a scalpel to make a cut in the circular internal anal sphincter muscle. It is important not to damage the external anal sphincter muscle which surrounds it. The surgery takes around 15 minutes to perform and patients can normally return home the same day. Most people make a full recovery and find that their anal fissure pain quickly improves.

Lateral internal sphincterotomy complications are rare but may include infection, pain and bleeding. Sometimes patients are left with a degree of incontinence, which might involve passing feces together with gas, or a small amount of involuntary soiling. Often, these problems are present immediately after surgery but resolve later. In a few patients, the anal fissure does not heal following lateral internal sphincterotomy, or the fissure recurs. Around half of cases where the fissure fails to heal are associated with an inflammatory condition of the bowel known as Crohn's disease.

The Health Board is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
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