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Anal Abscess/Fistula


What is a perianal abscess?
A perianal abscess is an infection in a mucous-secreting gland in the anal canal around your anus.

What is a perianal fistula?
A perianal fistula, almost always the result of a previous abscess, is a small passage connecting the anal gland from which the abscess arose to the skin where the abscess was drained.

What causes an abscess?
An abscess is formed when a small gland just inside the anus becomes infected from bacteria or stool trapped in the gland. You did nothing to cause this infection. Certain conditions — constipation, diarrhea, colitis, or other inflammation of the intestine, for example — may make these infections more likely.

What causes a fistula?
After an abscess has been drained, a passage may remain between the anal gland and the skin, resulting in a fistula. If the gland does not heal, there will be persistent drainage through this passage. If the outside opening of the fistula heals first, a recurrent abscess may develop.

What are the symptoms of an abscess or fistula?
Perianal abscesses are generally manifested by intense anal pain and swelling. Fever is possible. Drainage of the abscess, either on its own or with an incision, relieves the pain and pressure. Fistulas are associated with drainage of blood, pus, or mucus, but they are generally not painful.

Does an abscess always become a fistula?
No. A fistula develops in up to 50 percent of all abscess cases. There is no way to predict if this will occur. If drainage persists for two to three months, the diagnosis of perianal fistula is made.

How is an abscess treated? 
An abscess is treated by draining the pus through an opening made in the skin near the anus. Often this can be done in the doctor's office using a local anesthetic. A large or deep abscess may require drainage in the operating room. Hospitalization may be necessary for patients susceptible to more serious infections, such as diabetics or people with decreased immunity.

How is a fistula treated?
Surgery is generally necessary to treat a perianal fistula. This usually involves cutting a small portion of the anal sphincter muscle to open the passage, joining the external and internal opening, and converting the passage into a groove that will then heal from the inside out. Most fistula surgery can be performed on an outpatient basis. If the fistula involves too much sphincter muscle, a two-stage procedure or more complicated repair may be necessary.

What can I expect after fistula surgery?
Discomfort after fistula surgery can be mild to moderate for the first week and can be controlled with pain medication. The amount of time lost from work or school is usually minimal. There will be no limitation on activity. Soak the affected area in warm water three or four times a day. Stool softeners may also be recommended. You may need to wear a gauze pad or minipad to prevent the drainage from soiling your clothes. Bowel movements will not affect healing.

Will an abscess or fistula recur?
If proper healing occurs, the problem usually will not return. If your bowels are otherwise normal, you are probably not at higher risk for developing another abscess.

Learn more about Anal Abscess/Fistula from the American Society of Colon and Rectal Surgeons (ASCRS) Website