Anal Abscess & Fistula

An abscess is a collection of pus.  Abscesses may occur anywhere in the body after the early infection becomes localised.

Cause of an Abscess

There are a number of small glands just within the anal canal, which communicate between the lining of the anal canal and the muscular sphincters around the anal canal.  The bacteria accumulates in these glands and when these conditions are ripe an infection occurs.  As this infection becomes localised an abscess develops.  The tissues around the anus are loose and the abscess can spread deeper, involving the muscles and surrounding tissues.  The natural course of any abscess is to enlarge and rupture through the overlying skin or inwards into the anal canal and rectum.


As the abscess enlarges the pressure within the abscess increases and this causes severe pain.  There may be a throbbing pain and if it is a severe abscess then there may be an elevated temperature and night sweats.

Treatment of an Abscess

Initially antibiotics are often given but once an abscess stays these usually only contain the infection rather than cure it.  Thus surgical treatment and drainage is required.

For a small superficial abscess this can be done under Local Anaesthetic in the Surgeon’s office.  A larger abscess may require hospitalisation and drainage under General Anaesthesia.  Antibiotics by themselves do not cure an abscess.  They may control some of the fever and also the spread of infection into the general circulation.


Fistulas may occur in many sites of the body.  They are an abnormal track between two surfaces.  An anal fistula is track between the lining of the anal canal and the skin around the anus.  A fistula forms usually after an anal abscess has drained spontaneously or following surgery.  Because the track comes lined with chronic infection it tends not to heal up by itself and there is a persistent discharge of pus, which may settle temporarily but then recurs.  Fistulas can occur in association with other conditions such as inflammatory bowel disease e.g. Crohn’s disease or ulcerative colitis.  A fistula will not heal usually by itself and there are a variety of ways of treating fistulas depending on their size, length and how deep they are into the anal canal.  The more superficial fistulas are usually readily treated surgically.


A General Anaesthetic is usually required in hospital.  The track is completely opened up and allowed to heal by what is termed second intention healing.  This process does take some time and cannot be hastened by sewing up.

If the fistula passes through the muscle this muscle has to be divided and this makes the operation a little tricky because there is a slight risk if too much muscle is divided there can be a permanent leakage of fluid.  Thus particular care is required with this procedure.


A loop of flexible material is passed through the track and ties over the skin.  With time this cuts through the skin and the drainage allows the fistula to