Anal Abscess / Anal Fistula

What Is An Anal Abscess?

An abscess is a collection of pus in any localised space in the body. An anal abscess is one that develops in the tissues around the anus.

What Is The Cause Of An Anal Abscess?

A number of small glands are normally present between the inner and outer layers of the anal sphincter muscle. Bacteria may lodge in these glands, setting up an infection. An abscess develops from this infective process. This may extend to various areas around the anal canal to involve the anal sphincter muscle and surrounding structures. The abscess may enlarge and burst through the overlying skin or may be drained by surgical treatment.

What Are The Symptoms Of Abscess?

As the amount of pus in an abscess increases, the pressure within it rises. This produces constant throbbing pain which continues until the pus escapes. Other symptoms are fever and sweating.

How Is An Abscess Treated?

The pus is drained from the abscess cavity by making an opening through the overlying skin. This may be done under local anaesthesia in the doctor’s office. A large abscess may require wider drainage, under general anaesthesia. Hospital admission is needed for such a procedure. Antibiotics may be used to control the spread of infection, but antibiotics alone will not cure an abscess. Drainage of the pus is always necessary. 

What Is A Fistula?

An anal fistula is an abnormal track (“tunnel”) between the internal lining of the anus and the skin outside the anus. A fistula may develop after drainage of an anal abscess but may occur spontaneously. Discharge of pus may be constant or intermittent as the external opening on the skin may heal temporarily. 

Is A Fistula Related To Cancer?

No, a fistula is not related to cancer.

Is A Fistula Related To Other Diseases?

Most fistulae are the result of infections in an anal gland. However patients suffering from inflammatory bowel disease (Colitis and Crohn’s disease) are more likely to develop anal abscesses and fistulae.

How Is A Fistula Treated?

Surgery is needed to cure a fistula. The course of the track between the anus and the skin has to be identified and exposed. This track may be treated in one of three ways according to its complexity.

  • Fistulotomy opens the length of the track to the skin’s surface allowing the open wound to heal slowly. Some sphincter muscle is divided. This is the most common treatment employed.
  • A Seton is a loop of flexible material placed along the track to maintain drainage for a period of time.
  • Fistula repair closes the internal opening of the track and preserves anal sphincter muscle. This is a more complex operation. 

Examination under anaesthesia may be necessary to assess the process of healing. Most operations for fistulae are performed in hospital but small fistulae can be managed in Day Care Centres.

Anal fistula can be a difficult and frustrating condition for a patient, as healing rates are variable, and there is often the need for several surgeries in the situation of a complex anal fistula. As a patient, it is important that you receive a clear description of the likelihood of healing from your surgeon. Please discuss any concerns around this with your surgeon, in particular if the condition is affecting your mood and your ability to carry out your normal daily activities.

Anal Sphincter Control After Surgery

Fistulotomy divides a varying depth of anal sphincter and this may result in some weakness of the muscle. The effect on continence will depend on the anatomy of the fistula and the amount of intact sphincter remaining after surgical treatment.


Fistula: from Latin meaning pipe or read. Fistula surgery has been practised since ancient times and is mentioned in the Ebers Papyrus of 1550 B.C. from Egypt. Fistula instuments have been unearthed in the ruins of Pompeii. Hippocrates (460-356 B.C.) realised that an anal fistula required fistulotomy and also used the Seton technique. Henry V of England died of a fistula at the age of 35. Louis XIV of France had a fistula successfully treated in 1687 which did much to improve the lowly status of surgeons at that time.