An anal fissure is a small tear in the lining of the anal canal, usually at the very back of the anal opening. The fissure can be acute (coming on suddenly and lasting a short time) or chronic (longer lasting), and may be a disorder on its own or a symptom of another disorder, such as Crohn's disease or ulcerative colitis.

An anal fissure existing on its own (primary) is usually thought to be the result of straining - either from passing hard and large stool, or (more uncommon) from explosive diarrhea. It may also be due to the strain of childbirth.

Anal fissures are one of the most common causes of anal pain. They can occur at any age and often in people who are frequently or severely constipated. Many anal fissures heal with self-care steps, but some may require medication or surgery to relax the anal sphincter muscle.

How is an anal fissure diagnosed?

Diagnosis begins with a patient's history of the problem, but it must be confirmed by physical examination. Sometimes a fissure may be immediately visible. In other cases, a doctor might need an anoscope to view the anal canal.

To rule out other disorders, doctors might also use:

A proctoscope - To examine the rectum and lower portion of the colon
A flexible sigmoidoscope - A thin tube with a lighted camera inside the tip that allows doctors to view the lining of the rectum and sigmoid colon as a magnified image on a television screen.

The fissure's location can give doctors clues to whether the fissure might be a symptom of another disorder. A fissure that occurs at the side of the anal opening, rather than the back or front, is more likely to be a sign of another disorder, such as inflammatory bowel disease.

How is an anal fissure treated?

Acute anal fissures are usually initially treated with self-care procedures, while chronic, painful fissures may require medication or surgery. Treatment of acute anal fissures aims to break the cycle of passing hard stools (or explosive diarrhea) and the resulting pain and spasms.

Doctors generally recommend self-care procedures such as:

Soaking in warm water for 15-30 minutes to relax the anal sphincter muscle
Consumption of additional liquids and fiber
Stool bulking agents
Acetaminophen for pain; but avoiding aspirin and nonsteroidal anti-inflammatory drugs (NSAIDS), as they affect the blood's ability to clot and could delay healing
Hand washing the area with soap and water after bowel movements

Anal fissures which don't respond to self-care and become chronic can be treated with medication or possibly surgery.

Nitroglycerin or nifedipine paste might be prescribed to apply around the anus a few times a day. The paste relieves pressure in tissue around the fissure and increases blood flow to promote healing. Temporary headaches or light-headedness from the paste are possible side effects.

When self-care procedures and medication do not heal an anal fissure, surgery may be an option.

Lateral Internal Sphincterotomy

"Lateral" refers to side, and "internal sphincterotomy" refers to the cutting of a small portion of the inner part of the sphincter muscle. While fissures usually occur in the back or front of the anus, cutting the sphincter muscle at the side is still effective in relaxing the anus and encouraging the fissure to heal without creating another wound near the fissure. The surgery has a very high success rate with a very small risk for gas or stool incontinence or recurrence. It's usually an outpatient procedure, performed under general, regional or local anesthesia.