NWCRC: What We Treat

What is an anal abscess/anal fistula?

An anal abscess is a painful, infected cavity filled with pus located near the anus or rectum. If the abscess is large, a person may develop fever, chills or a general ill feeling. An anal fistula is a small tunnel which starts inside the anus and usually exits at one or more places on the skin of the buttocks outside the anus. A fistula almost always is the result of a previous abscess. A fistula may cause irritation to the skin around the anus, itching or drainage of stool or mucous.

What causes an anal abscess?
An abscess is caused by an infection of a small gland just inside the anus. Bacteria or foreign matter enters the tissue through the gland. Certain conditions, such as colitis, can sometimes make these infections more likely.

How is an anal abscess treated?
In order for an abscess to heal, the pus must be released from the cavity. This usually is done by making an opening through the skin near the anus to relieve pressure and allow the pus to drain. If the abscess is small and near the surface of the skin, this usually can be accomplished in the doctor's office using a local anesthetic. A very large or deep abscess may require more extensive anesthesia. In those circumstances, the drainage procedure usually is performed in the hospital. Antibiotics, for the most part, are unnecessary and are not an alternative to draining the pus.

How long will it take before I feel better?
When the pus is allowed to drain, relief is rapid and dramatic. The abscess may continue to drain for several weeks until all the infection is gone and the cavity which contained the pus has a chance to heal.

What should be done at home while the abscess cavity is healing?
Soaking the affected area in warm water (a sitz bath) for 20 minutes, three to four times a day, will help ease pain and speed healing. This should be done for as long as the area is uncomfortable. Drainage may continue for several weeks and is a healthy sign of healing. It may be necessary to wear a light gauze dressing or mini-pad inside the underwear to keep the drainage from soiling clothing. Bowel movements will not affect the healing process.

Does an anal abscess always become an anal fistula?
About half of the people who get an abscess will ultimately develop a fistula. There usually is no way to predict who will and who will not develop a fistula.

How long will it take to find out whether I will have a fistula?
Usually this is evident by 4 to 6 weeks after the abscess is drained, though anal fistulas occasionally may develop months or years later. Sometimes a fistula is discovered only after the development of another abscess in the same area.

How is an anal fistula treated?
Fistulas require a surgical procedure for treatment. This surgery almost always can be performed in an Outpatient Surgery Department without the need for an overnight hospital stay. The discomfort after such a procedure is mild to moderate and usually is easily controlled by pain pills for a few days. The amount of time lost from work typically is minimal. This surgery usually does not interfere with one's ability to control bowel movements.