Anal fistula treatment

An anal fistula is a connection or tunnel that develops between the bowel (anal canal) and the skin of the anus (bottom). It can often be seen as a small hole near your anus (where poo leaves the body) 

There are different types of fistulas. They can be a simple tunnel linking your anus and skin, or more complex tunnels that branch off in different directions. 

Some fistulas run through the sphincter muscles which surround the anus. The sphincter muscles open and close the anus.

Fistulas very rarely heal by themselves, and surgery is the only way to treat them.

Causes of an anal fistula

A fistula can form because of intestinal diseases, such as Crohn’s disease.

1 in 2 cases happens from an infection around the anus which causes an abscess.

An abscess is a painful swollen area containing pus, a yellow-green liquid. An abscess in the anus can happen when a small gland becomes infected. When an abscess discharges its pus, it may cause a fistula.  

Fistulas can also form from a previous abscess that has not fully healed after being drained.

Symptoms of an anal fistula

The main symptoms are pain and pus (sometimes blood-stained) leaking from the fistula. 

This leakage often relieves the pain. If there is an abscess, there will also be swelling around the anus. 

The NHS website has more information about symptoms of an anal fistula.


Surgery is the only way to treat a fistula. It aims to help your symptoms, and remove the tracts and any infection. If you do not have the surgery, your fistula is unlikely to heal.

There are different procedures. The surgery you have depends on the position of the fistula and if it's a single channel or branches in different directions. Your surgeon will talk to you about surgery, and recommend the best surgery for you.

During surgery the infected tract is cut or ‘laid open’ to stop unhealed pockets of infection from being trapped inside. If an abscess is found, this is cut open and drained first, before the fistula is laid open.

Surgery for an anal fistula is done under general anaesthetic.

Read more about having surgery for an anal fistula

Risks of surgery

Your surgeon will talk to you about the possible risks of surgery, before asking you to sign a consent form. 

The risk of complications for this type of surgery depend on where your fistula is. If the fistula is deep or complex, there might be more risk of damage to your anal sphincter muscles, which are important for controlling your bowels. 

In most cases, surgery does not involve cutting a significant section of these muscles. However, you should be aware that any damage to the sphincter muscles can lead to a change in your ability to control wind or poo (bowel incontinence). 

We want to involve you in decisions about your care and treatment. If you decide to have surgery, you will be asked to sign a consent form to say that you agree to have the treatment and you understand what it involves. 

If you would like more information about our consent process, speak to a member of staff caring for you.

Resource number: 0908/VER6
Last reviewed: March 2022
Next review: March 2025

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