Overview

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 that connects your anus and skin
• more complex tunnels that branch off in different directions

Some fistulas run through the sphincter muscles that surround the anus. These muscles open and close the anus.

Fistulas rarely heal by themselves. Surgery is the only way to treat them.

Causes of an anal fistula

You can get a fistula because of digestive conditions, such as Crohn’s disease. This is a lifelong condition where parts of the digestive system become inflamed.

1 in 2 cases are caused by an infection around the anus that makes you get an abscess.

An abscess is a painful swollen area that contains a yellow-green liquid called pus. You can get an abscess in the anus if a small gland becomes infected. When an abscess leaks pus, this may cause a fistula.

You can also get a fistula if a previous abscess 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 eases the pain. If you have an abscess, there will also be swelling around the anus. 

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

Treatment for an anal fistula

Surgery is the only way to treat a fistula. The aim of surgery is to help your symptoms, and remove the tunnels and any infection. If you do not have the surgery, your fistula is unlikely to heal.

There are different procedures. The surgery that you have depends on:

• the position of the fistula
• if the fistula is a single tunnel or branches in different directions

Your surgeon talks to you about surgery and recommends the best option for you.

During surgery, we cut or 'lay open' the infected tunnel to stop unhealed pockets of infection from being trapped inside. If we find an abscess, we cut open and drain this first before laying open the fistula.

You have surgery for an anal fistula under a general anaesthetic. This is a medicine that makes you sleep and stops you feeling any pain during the procedure.

Most people do not need to stay in hospital overnight unless the surgery is more complex.

Read more about having surgery for an anal fistula. 

Risks of surgery

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

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

In most cases, surgery does not involve cutting a big section of the anal sphincter muscles. However, any damage to these muscles can make it harder for you to control wind or poo (bowel incontinence). 

After surgery there is a risk of:

• pain
• infection
• bleeding
• fistula returning

Giving your permission (consent)

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

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