An anal fissure is a tear in the internal lining of the anus. This area is called the anal mucosa. This break in the anal lining often reopens during bowel movements. The result is bright red blood and intense pain.

What is going on in the body?

An anal fissure is a tear in the bowel lining. It causes painful, bloody bowel movements. It is often confused with hemorrhoids, which are painful swellings at the anus caused by enlarged veins. A fissure can be acute or chronic. The chronic condition is often associated with a buildup of tissue at the external end of the tear. This is called a sentinel pile and may be noticed by an affected person. The internal end may also have a buildup of tissue that an affected person can rarely see.

When a fissure is present, the mucosa of the anus opens each time it is stretched to allow for a bowel movement. This continual opening prevents healing. It can also leave scar tissue. Most chronic fissures are in the center of the back of the anus.

The anal sphincter muscles need to relax for a person to have a bowel movement. A person with a fissure may have muscles that are too tight. This makes bowel movements painful.

What are the causes and risks of the condition?

Anal fissures are usually related to abnormal bowel movements. Constipation or frequent stools can cause straining and worsen the problem. Injury to the anal area can also damage the anal mucosa. Pregnancy or difficult delivery is often a cause of this trauma. There are also several medical conditions that can cause anal fissures, including:

Venereal warts, which are sexually transmitted warts caused by a virus, can look like anal fissures and may have similar symptoms.