Anal Fistula

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An anal fistula is an abnormal tunnel connecting the skin near the anus with the inner lining of the rectum. It is usually the result of an infection near the anus causing a collection of pus, called a perianal abscess. After the pus has been drained away, an abnormal tunnel remains.

Anal fistulas can also be a result of inflammatory conditions such as tuberculosis or inflammatory bowel disease.

Anal Fistula Treatment
Spider Vein Treatment Procedure


Common symptoms of an anal fistula include:

  • Swelling around the anus
  • Discharge from the swelling
  • Passage of blood from the swelling
  • Skin irritation around the anus
  • Constant pain that is worse with sitting down or bowel movement
  • Fever (with swelling around the anus)

When to Seek Treatment

  • Pain
  • Persistent smelly discharge around the anus


The key finding from an examination is the presence of one or more small holes in the skin near the anus.

An MRI or ultrasound may be performed to confirm the diagnosis.


Surgery is usually recommended as it is the most effective treatment. An anal fistula rarely heals by itself.

The aim of surgery 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.

There are many types of surgical procedures available but the choice depends largely on the type of abnormal tunnel.

Superficial Tunnels- Fistulotomy
The abnormal tunnel is opened up to allow drainage.

Superficial Tunnels- Fistulectomy
The abnormal tunnel is removed.

Deeper or Multiple Tunnels
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, 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 is very deep. The fistula can recur despite surgery. There is also a risk of damage to the muscles controlling bowel movement (anal sphincters), and thus risk of faecal incontinence. Fortunately, this is very rare.


  • Constipation
  • Diarrhoea
  • Childbirth

Risk Factors

  • Inflammatory bowel disease
  • Tuberculosis
  • Anal cancer
  • STDs

Consult Our Doctor

Dr Jane Tan Jye Yng
Colorectal & General Surgeon

MBBS (Singapore), M.Med (Surgery), MRCS (Edin), FAMS (Surgery)


Avoiding standing still for long periods will reduce the pressure in the veins in the legs. For people who need to stand for long periods at work, wearing compression stockings will reduce the pressure build up in the legs.

The ultrasound will be done of the legs from the thigh to the calves. Please wear or bring along a pair of shorts to change into for the scan.

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