What is an anal fissure?

An anal fissure is a tear in the lining of the lower rectum (anus) that causes pain during bowel movements. It is a common condition. Anal fissures do not lead to more serious conditions such as colon cancer.

Most anal fissures heal with home treatment after a few days or weeks (acute anal fissures). Occasionally a fissure takes more than 6 weeks to heal (chronic anal fissure), in which case it usually requires medication to heal. Surgery may be necessary for fissures that do not heal with medication.

Anal fissures affect people of all ages, particularly young and otherwise healthy people. They are equally common in men and women.

Sometimes an anal fissure and a hemorrhoid develop at the same time.

What causes an anal fissure?

Anal fissures are caused by vigorous stretching of the anal canal. A fissure may develop if you are constipated and try to pass a large, hard stool; if you don't relax your anal muscles (sphincter muscles) during a bowel movement; or sometimes after repeated diarrhea.

Many experts believe the most common cause is excessive tension in the two muscular rings (sphincters) controlling the anus. The external anal sphincter is under your conscious control. However, the internal anal sphincter is not under your control. This muscle remains under pressure, or tension, all of the time. A fissure may develop if the internal sphincter's resting pressure becomes too high, causing spasm and reducing blood flow to the anus.

Trauma also can cause fissures. During childbirth, 11% of women develop anal fissures.¹ Fissures can also be caused by digital insertion (as during an examination), foreign body insertion, or anal intercourse.

In some cases, an anal fissure may be caused by Crohn's disease, an inflammatory bowel disease (IBD) that causes bloody diarrhea, abdominal pain, fever, weight loss, and fissures or fistulas near the anus.

A low-fiber diet may play a role in the development of fissures.

What are the symptoms?

An anal fissure causes a sharp, stinging, or burning pain during a bowel movement. The pain, which can be severe, may last for a few hours.

Fissures may itch. They often bleed lightly or cause a yellowish discharge. You may see a small spot of bright red blood on toilet tissue or a few drops in the toilet bowl. The blood is separate from the stool. Blood mixed with stool indicates some other condition, possibly inflammatory bowel disease (IBD) or colon cancer. You should contact a health professional if you have bleeding with bowel movements or dark, bloody stools.

Occasionally an anal fissure may be a painless wound that won't heal and that bleeds intermittently but causes no other symptoms.

How is an anal fissure diagnosed?