Anal Abscess (and Anal Fistula)En Español (Spanish Version)
An anal abscess is a pus-filled glandular cavity near the anus, either deep in the rectum or close to the anus opening. When the abscess opens to the surface and fails to heal, a fistula occurs. The fistula will often drain pus or fecal material.
Since some abscesses require surgery, talk to your doctor right away if you think you may have this condition.
Abscesses result when bacteria infect a mucus-secreting gland in the anus or rectum, causing blockage and damage to surrounding intramuscular tissue. The reason why the infection occurs is unknown because, normally, this area is free from infection.
A risk factor is something that increases your chance of getting a disease or condition.
The following factors increase your chance of developing an anal abscess. If you have any of these risk factors, discuss them with your doctor:
If you experience any of these symptoms, do not assume it is due to an anal abscess. These symptoms may be caused by other health conditions. If you experience any one of them, discuss them with your doctor.
Abscess located near the surface of the skin on the buttocks:
- Pain and tenderness radiating from the location of the abscess
- Visible redness and swelling
Abscess located deeper within the rectum:
- Pain in the lower abdomen
- Swelling in the rectum that can be seen during examination of the rectum
Your doctor will ask about your symptoms and medical history, and perform a physical exam. While your doctor will be able to see an abscess near the surface of the skin, he may need to exam the rectum with a gloved finger to determine the presence of a deeper abscess. Tests that may be done include:
Treatment normally consists of draining the abscess, which is done by making an incision through the skin near the anus into the abscess. For this, you will be given local anesthesia. In rare cases, admittance to a hospital is required, as well as
Antibiotics may be given to reduce fever or under other special circumstances.
If you have Crohns disease, your doctor will give you medicine to treat this condition.
Following drainage (or natural rupture) of an abscess, more than half the cases will develop into anal
fistulas—usually occurring weeks but sometimes years later. In this condition, a permanent abnormal channel is formed from the site of the original abscess to the surface of the skin near the anus. This channel (fistula) allows for the continuous drainage of the abscesses’ pus-like fluid. In the case of a fistula, surgery to remove and close-up the channel is normally recommended. In rare cases, the fistula (and stool incontinence) will return after surgery.
If you are diagnosed with an anal abscess or fistula, follow your doctor's
Copyright © Nucleus Medical Media, Inc.
There are no known ways to prevent anal abscesses or subsequent fistulas because the cause of the original infection of anal glands is unknown.
American College of Gastroenterology
American Society of Colon and Rectal Surgeons
Canadian Association of Gastroenterology
Anal abscess/fistula. American Society of Colon and Rectal Surgeons website. Available at:
November 25, 2006.
Anal rectal abscess and fistula. Hemorrhoid.net website. Available at:
http://www.hemorrhoid.net/abscess.php. Accessed Nov. 29, 2006
Anorectal abscess. The Merck Manuals Online Medical Library website. Available at:
November 28, 2006.
Caliste X, Nazir S, et al. Sensitivity of computed tomography in detection of perirectal abscess.
Common gastrointestinal problems: rectal complaints. American College of Gastroenterology website. Available at:
http://www.acg.gi.org/patients/cgp/cgpvol3.asp#rectal. Accessed Nov. 28, 2006
Fistual-in-ano. DynaMed website. Available at:
Accessed November 25, 2006.
Schaffzin DM, Wong WD. Surgeon-performed ultrasound: endorectal ultrasound.
Surg Clin North Am.
Sun MR, Smith MP, et al. Current techniques in imaging of fistula in ano: three-dimensional endoanal ultrasound and magnetic resonance imaging.
Semin Ultrasound CT MR.
Last Reviewed October 2012