Symptoms of an anal fistula include skin irritation around the anus, a throbbing pain, and a discharge of pus or blood when you have a bowel movement.
There are several common symptoms of an anal fistula.
- skin irritation around the anus (the opening where waste leaves the body)
- a throbbing, constant pain that may be worse when you sit down, move around, have a bowel movement or cough
- a discharge of pus or blood when you have a bowel movement – read more information about rectal bleeding
If your fistula was caused by an abscess that you still have, you may have:
- a high temperature of 38ºC (100.4ºF) or over
- a general feeling of being unwell
If your fistula was caused by inflammation of the intestines (part of your digestive system) – for example, because of a condition such as Crohn's disease – you may also have:
Read more information about the causes of an anal fistula.
Types of fistula
An anal fistula is usually classified as:
- simple or complex – depending on whether there is a single fistula tract or interlinking connections
- low or high – depending on its position and how close it is to the sphincter muscles
The sphincter muscles are two rings of muscles that open and close the anus. They are known as the internal and external sphincter muscles.
The most common types of anal fistula are:
- intersphincteric fistula – the fistula tract (channel) crosses the internal sphincter and opens on the surface of the skin next to the anus
- transsphincteric fistula – the fistula tract passes through both the internal and external sphincters and opens on the surface of the skin next to the anus
Other types of anal fistula can:
- begin at a different part of the colon (large intestine)
- extend in a different direction so the fistula does not open next to the anus
- develop in a horseshoe shape, with two open ends either side of the anus
Surgery is usually necessary to treat an anal fistula because very few will heal by themselves. The procedure used is usually a fistulotomy.
Surgery is usually necessary to treat an anal fistula as very few heal by themselves.
The type of surgery you have will depend on the position of your fistula and whether it is classed as simple or complex. Your surgeon will be able to explain the procedure to you in more detail.
The aim of surgery is to heal the fistula while avoiding damage to the sphincter muscles (the ring of muscles that open and close the anus). Damage to the sphincter muscles could lead to bowel incontinence, where you do not have control over your bowels.
Read more about complications of an anal fistula.
Surgery for an anal fistula is usually carried out under a general anaesthetic, where you are unconscious and cannot feel anything. In some cases a local anaesthetic is used, where you are conscious but the area being treated is numbed so you do not feel any pain.
Some of the different types of anal fistula surgery are explained below.
A fistulotomy is the most commonly used type of anal fistula surgery, used in 85-95% of cases.
It involves cutting open the whole length of the fistula, from the internal opening to the external opening. The surgeon will flush out the contents and flatten it out. After one to two months, the fistula will heal into a flat scar.
To access the fistula, your surgeon may have to cut a small portion of the anal sphincter muscle. However, this will depend on the position of the fistula. Your surgeon will make every attempt to reduce the likelihood of bowel incontinence.
Your surgeon may decide to use a seton during your surgery. A seton is a piece of surgical thread that is left in the fistula tract to keep the tract open, often for several months. This allows it to drain properly before it heals.
This may be considered if you are at high risk of developing incontinence – for example, because your fistula crosses your sphincter muscles.
It is also sometimes used to allow secondary tracts to heal before further surgery is carried out on the main tract. It can also be used to divide the sphincter muscle, which allows it to heal between operations.
If your surgeon is planning to use a seton, they will discuss this with you. In some cases, it may be necessary to have several operations to treat your fistula using seton techniques.
Advancement flap procedures
Advancement flap procedures may be considered if your fistula is complex or there is a high risk of incontinence.
An advancement flap is a piece of tissue that is removed from the rectum or from the skin around the anus.
During surgery, the fistula tract is removed (a procedure called fistulotomy). The advancement flap is then attached to where the internal opening of the fistula was.
A bioprosthetic plug is a cone-shaped plug made from animal tissue. It can be used to block the internal opening of the fistula.
Stitches are used to keep the plug in place, but the external opening is not completely sealed so the fistula can continue to drain. New tissue then grows around the plug to heal it.
However, this procedure can sometimes lead to complications, such as:
- pain and increased drainage – this may require treatment with antibiotics
- a new abscess forming
- the plug being pushed out of place
Read the National Institute for Health and Care Excellence (NICE) guidance on closure of anal fistula using a suturable bioprosthetic plug.
Two trials using bioprosthetic plugs have reported success rates of more than 80%. However, there is still uncertainty over the recurrence rates and long-term outcomes.
Fibrin glue is currently the only non-surgical option for treating an anal fistula. The fibrin glue is injected into the fistula to seal the tract. It is injected through the opening of the fistula and the opening is then stitched closed.
Fibrin glue may seem an attractive option as it is a simple, safe and painless procedure. However, the long-term results for this treatment method are poor. For example, one small study had an initial success rate of 77%, but after 16 months only 14% of people were still successfully healed.
Several clinical trials are currently taking place to compare the different types of treatment for an anal fistula. You may be asked to take part in one.
Read more information about taking part in a clinical trial.
If you are interested, you will be given information about the particular trial and asked for your consent.
Before giving your consent, make sure that you are fully aware of everything the trial involves. Feel free to decline if you do not wish to take part.
Read a list of current clinical trials for anal fistula.