Anal Fistula

An anal fistula is an abnormal tunnel connecting the skin near the anus with the inner lining of the rectum.

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Understand your Problems

Anal fistula is usually the result of an infection near the anus causing a collection of pus, called a perianal abscess.  This is like a big pimple near the anus. After the pus has been drained away, an abnormal tunnel remains. Anal fistula can also be a result of inflammatory conditions such as tuberculosis or inflammatory bowel disease.


Common symptoms include skin irritation around the anus, and a constant pain that is worsened when you sit down or move your bowel. There is usually a smelly discharge. Occasionally there may be passage of blood. So the patient would complain his underwear is often stained. The abscess may recur and the patient will complain of worsening pain, fever and swelling around the anus. The key finding is the presence of one or more small holes in the skin near the anus. Pressing on the skin around these holes may cause a bloody or smelly discharge from these holes.

Seeking a medical consult

If you complain of pain or a persistent smelly discharge around the anus, you should see a doctor. If the doctor confirms the diagnosis of an anal fistula, surgery is usually recommended as it is the most effective treatment. Anal fistula rarely heals by itself.


There are different types of surgical procedures available. The aim is to disconnect the tunnel. Special care has to be taken not to damage the anal muscles (anal sphincter) as the anal sphincter controls bowel continence.


The choice of procedure depends largely on the type of the abnormal tunnel.


If the tunnel lies close to the skin, the surgery is straightforward, and involves opening up the abnormal tunnel to allow drainage (called Fistulotomy) or the removal of the whole tunnel (Fistulectomy).


If the tunnel lies very deep, or if there are multiple tunnels, we may have to choose other techniques. Such techniques may include the insertion of a specialised surgical thread called a seton, or filling the tunnel with a special glue or tying the tunnel (LIFT procedure). All these procedures have different risks and benefits. However, in general, most of these procedures may be performed as a Day Surgery procedure. If admission is required, the average length of stay is one night.


Some patients may require multiple operations especially if there are multiple tunnels or if the tunnel lies very deep. As with any type of treatment, surgery for anal fistula also carries some risks. The fistula can recur despite surgery. There is also a risk of damage to the muscles controlling bowel movement (anal sphincters), and thus a risk of faecal incontinence. Fortunately, this is very rare.

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