Anal Fistula

An anal fistula is a tunnel or communication between the inside of the anal canal and the outside skin. 

There are multiple different paths this communication can take.  This is known as the fistula tract.

Everyone has two circular muscles around the anus.  This is known as the anal sphincter and allows one to have control over their bowels and flatus (wind).  A fistula tract may pass through around or in-between these muscles.

Anal fistula are known as peri-anal fistula or fistula-in-ano.

What causes an anal fistula?

The most common cause of an anal fistula is a previous anal abscess.  Whilst most anal abscesses heal completely after appropriate treatment, up to 40% of cases may become an anal fistula.

Less commonly, an anal fistula may be associated with other causes, such as bowel conditions, previous trauma or surgery in nearby areas or radiotherapy.

What are the symptoms of an anal fistula?

Common symptoms of an anal fistula include a persistent skin opening (of variable size) or fluid discharge from the site of previous anal abscess surgery, discomfort around the anus and skin irritation around the anus.  Sometimes, an anal fistula may close on its own and re-open at a later time.  This may produce symptoms that come and go.

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How is an anal fistula diagnosed?

An anal fistula is usually diagnosed on inspection and examination of the perianal area.  This may require an experienced colorectal surgeon to identify. 

Other tests may be required, such as a 3-dimensional ultrasound of the anus and rectum, or an MRI scan. 

Sometimes, a minor surgical procedure may be needed to identify a fistula.

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How is an anal fistula treated?

An anal fistula almost always requires surgery for cure.  There is currently no medication available to cure an anal fistula.  Sometimes more than one procedure is required to treat an anal fistula.

Firstly, the fistula tract and whether it involves the anal sphincter needs to be clarified.  Any associated infection also needs to be eliminated.  This is best achieved by putting a thin piece of elastic material or suture through the fistula tract.  This is known as a seton.

After this, there are several possible surgical treatment options.  The choice should be personalized to each patient, based on factors including the location and amount of anal sphincter involved in the fistula tract, each patient’s individual bowel function and other medical conditions (if present).

It is recommended that anal fistula surgery be performed by a specialist colorectal surgeon to achieve optimal results.

Dr Zhu is a specialist colorectal surgeon and has extensive experience in the treatment of anal fistula.  Dr Zhu can assess your symptoms and recommend a personalized treatment plan.