Anal Fistula


An anal fistula is a tunnel between the anal canal and the skin near the anus. It may appear as a small hole in the anal area. Fistulas vary a great deal, from a single simple channel to quite complex structures involving several connecting tracts. They also vary in how much sphincter muscle is involved, which is important in recommending specific treatments.


Most fistulas are the result of infection, and they are common in patients who have previously suffered from anal abscess. They also occur quite frequently in patients who suffer from bowel problems such as Crohn’s disease.


Typically, symptoms involve a cycle of swelling, tenderness and discharge of pus or blood. It is common to experience discomfort (often worse when you sit down or pass a bowel movement), and a discharge of blood or pus on bowel movement. Skin irritation around the anus is also common.


Your surgeon will carry out a physical examination at your consultation. He or she may use a proctoscope to get a detailed view. This is not usually painful unless an abscess is present, but if so it is possible to arrange to have this examination under general anaesthetic


Surgical treatment is usually necessary as few fistulas heal by themselves. Unfortunately it is often necessary to have a series of staged procedures to clean, drain and prepare the fistula for healing. The aim is to break the cycle of infection, draining and reinfection which prevents healing happening naturally, whilst minimising risk of damage to anal sphincter muscles which can cause incontinence.

The first stage is to confirm diagnosis and to control any infection. This is usually done under general anaesthetic using a seton drain. This is where a piece of soft elastic drain is placed through the fistula (or parts of the fistula if it is complex) to keep it open for long enough for the pus to drain easily.

Once the inflammation has settled due to the seton, your surgeon will be able to assess the complexity and location of your fistula. We usually wish to reassess and discuss options with you at this stage. It may be useful to have an anorectal physiology and endoanal ultrasoundtest to assess your anal sphincter function. In complex cases an MRI scan might be necessary.

Laying open of the fistula (‘fistulotomy’) may be an option. Under general anaesthetic, the fistula is opened up or ‘laid open’, converting it into a small wound which should heal after a few weeks. This may only be appropriate for patients where the risk of sphincter damage from this procedure is deemed very low.

LIFT procedure (ligation of intersphincteric fistula tract) is an operation in which the fistula is approached from the area between the internal and external sphincter muscles. The fistula in the internal sphincter fistula is tied off and the fistula in the external sphincter is removed. This is a relatively new procedure with very encouraging results.

An advancement flap is an operation in which a flap of tissue from the rectum or skin around the anus is freed up and ‘advanced’ to cover the internal opening inside the anus.

Alternatively, a variety of fillers and plugs may be used. A collagen plug is a cone-shaped plug made of collagen derived from animal tissue which is inserted into the fistula. It is stitched in place internally, leaving an opening on the outside so that possible infection can drain. During healing, new tissue grows into and replaces the plug. It does not need to be removed. This procedure has the advantage of involving no surgical incision and thus having a very low risk of sphincter damage. However, it may not be as effective as other surgical techniques and recurrence of the problem may be more frequent after this operation.

Fibrin glue or collagen paste are biological pastes which are injected into the fistula to seal the channel. These are safe and painless methods of treatment, but although they provide a good short term solution, the long term results are poor: a majority of patients have a recurrence of their fistula after one or two years.

It is important to be aware that many factors influence which course of treatment will be best suitable for you, and there may not be a hard and fast ‘correct’ course of action. Your surgeon will guide you through the best pathway for you.

Please be advised that the information on this website is not a substitute for professional medical advice, diagnosis or treatment