An anal fissure is a split or tear in the lining of the anal canal (rectal opening).
A fissure most commonly occurs after an episode of constipation, but it can happen after an attack of diarrhea. A fissure begins on the surface and usually heals rapidly on its own. Sometimes fissures may deepen to reach the underlying sphincter muscle (the muscle around the anal canal). It is not completely understood why some fissures heal and others do not. One major factor is persistent constipation or diarrhea, which can prevent healing. In addition, each time stool passes, the muscle goes into spasm, tightening the anal canal. If the sphincter muscle does not relax and the anal canal remains too tight, the fissure opens again with each bowel movement.
Rarely, a fissure can be caused by Crohn's disease or an infection. Treatment for the underlying disease usually relieves the fissure. Fissures very rarely become infected and they do not become cancerous.
Most superficial fissures heal without treatment, but some become chronic and cause ongoing discomfort. The first step is to correct the constipation or diarrhea and treat any underlying disease. A high-fiber diet or dietary bulk agent with plenty of fluids is recommended. A topical anesthetic ointment may help relieve the pain. The spasm may also be relieved by sitting in a warm bath several times a day. These measures usually result in healing. If they do not or the symptoms return, surgery may be required. Your doctor will discuss this with you.