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Anorectal Abscess

By

Parswa Ansari

, MD, Hofstra Northwell-Lenox Hill Hospital, New York

Last full review/revision Feb 2021| Content last modified Feb 2021
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Topic Resources

An anorectal abscess is a pus-filled cavity caused by bacteria invading a mucus-secreting gland in the anus and rectum.

  • Bacteria infect a blocked gland in the anus or rectum and create an abscess.

  • The infection produces pus and causes pain and swelling.

  • The diagnosis is based on an examination and the results of imaging tests if needed.

  • Cutting and draining the abscess is the best form of treatment.

The rectum is the section of the digestive tract above the anus where stool is held before it passes out of the body through the anus. The anus is the opening at the end of the digestive tract where stool leaves the body. (See also Overview of the Anus and Rectum Overview of the Anus and Rectum The anus is the opening at the end of the digestive tract where stool leaves the body. The rectum is the section of the digestive tract above the anus where stool is held before it passes out... read more .)

The Digestive System

Locating the Rectum and Anus

An abscess may be deep in the rectum or close to the opening of the anus. An abscess develops when a mucus-secreting gland in the anus or rectum is blocked, and bacteria grow and multiply. Although the anus is an area that is rich in bacteria, infection generally does not occur because blood flow to the area is rich. When infection does occur, it usually is caused by a combination of different types of bacteria.

Symptoms of Anorectal Abscess

Abscesses just under the skin can be swollen, red, tender, and very painful. Rarely, people have fever.

Abscesses deep in the rectum may be less painful but may cause fever and pain in the lower abdomen.

Diagnosis of Anorectal Abscess

  • A doctor's evaluation

  • Rarely computed tomography

A doctor can usually see an abscess if it is in the skin around the anus. When no external swelling or redness is seen, however, a doctor can make the diagnosis of anorectal abscess by examining the rectum with a gloved finger. A tender swelling in the rectum indicates an abscess.

Treatment of Anorectal Abscess

  • Cutting and draining the abscess

  • Antibiotics for some people

Antibiotics are typically given only to people who have fever, a weakened immune system, diabetes, cellulitis, or an infection elsewhere in the body. People who have an abnormally low number of a type of white blood cell (neutropenia Neutropenia Neutropenia is an abnormally low number of neutrophils (a type of white blood cell) in the blood. Neutropenia, if severe, significantly increases the risk of life-threatening infection. Neutropenia... read more Neutropenia ) are given antibiotics but usually do not have the abscess drained.

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