ANAL ABSCESS/FISTULA

A patient who feels ill and complains of chill, fever and pain in the rectum or anus could be suffering from an anal abscess or fistula. These medical terms describe common ailments about which many people know little.

What is an anal abscess?

An anal abscess is an infected cavity filled with pus found near the anus or rectum.

What is an anal fistula?

An anal fistula, almost always the result of a previous abscess, is a small tunnel connecting the anal gland from which the abscess arose to the skin of the buttocks outside the anus.

What causes an abscess?

An abscess results from an acute infection of a small gland just inside the anus, when bacteria or foreign matter enters the tissue through the gland. Certain conditions – colitis or other inflammation of the intestine, for example – can sometimes make these infections more likely.
 

 

 What causes a fistula?

After an abscess has been drained, a tunnel may persist connecting the anal gland from which the abscess arose to the skin. If this occurs, persistent drainage from the outside opening may indicate the persistence of this tunnel. If the outside opening of the tunnel heals, recurrent abscess may develop.

What are the symptoms of an abscess or fistula?

Symptoms of both ailments include constant pain, sometimes accompanied by swelling. This is not necessarily related to bowel movements. Other symptoms include irritation of skin around the anus, drainage of pus (which often relieves the pain), fever and feeling poorly in general.

 

Does an abscess always become a fistula?

No. A fistula develops in about 50% of all abscess cases, and there is really no way to predict if this will occur.

How is an abscess treated?

An abscess is treated by draining the pus from the infected cavity, making an opening in the skin near the anus to relieve the pressure. Hospitalisation may also be necessary for patients prone to more serious infections, such as diabetics or people with decreased immunity. Antibiotics are not usually an alternative to draining the pus, because antibiotics are carried by the blood stream and do not penetrate the fluid within an abscess.

The surgeon who drains your abscess will send a sample of the pus to the laboratory to see what sort of organisms are causing this. Generally, you will go home next day with arrangements for change of dressings made by the nursing staff. You will be requested to attend the out patient clinic in 10 days time for the results of the pus swab and depending on those results you may be asked to come back for a thorough examination under anaesthesia (EUA). This examination is to look for a possible fistula. 

 

What about treatment for a fistula?

Surgery is necessary to cure an anal fistula. Although fistula surgery is usually relatively straightforward (in the majority of cases), the potential for complication exists, and is preferably performed by a specialist in colon and rectal surgery. It is not advisable to perform at the same time as the abscess surgery. Fistulae often develop four to six weeks after an abscess is drained sometimes even months or years later. Fistula surgery usually involves cutting a small portion of the anal sphincter muscle to open the tunnel, joining the external and internal opening and converting the tunnel into a groove that will then heal from within outward. Most of the time, fistula surgery can be performed on a day surgical unit under anaesthesia – or with a short hospital stay. However complex fistulae will need more than simple laying-open. It may require longer hospital stay and a rubber sling (seton) inserted into the tract. The precise details of the procedure will be explained to you by the Colorectal surgeon or one of his team.

 

How long does it take before patients feel better?

Discomfort after fistula surgery can be mild to moderate for the first week and can be controlled with pain killers. The amount of time lost from work or school is usually minimal.

Treatment of an abscess or fistula is followed by a period of time at home, when soaking the affected area in warm water (sitz bath) is recommended three or four times a day. Stool softeners may also be recommended. It may be necessary to wear a gauze pad or surgipad to prevent the drainage from soiling clothes. Nursing staff on the ward will be able to give you a few of these on discharge until the district nurse visits you. Bowel movements will not affect healing.

 

What are the chances of a recurrence of an abscess or fistula?

If properly healed, the problem will usually not return. However, it is important to follow the directions of a colon and rectal surgeon to prevent recurrence.