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Anal fistula

If you would like to know about anal fistula surgery, the reasons for an anal fistula operation and the benefits of anal fistula surgery, the following information will interest you.


Before you agree to have your anal fistula operation it is important to know all you can about it. The information here is a guide to common medical practice. Each hospital and doctor will have slightly different ways of doing things when carrying out anal fistula surgery, so you should follow their guidance where it is different from the information given here. Because all patients, conditions and treatments vary it cannot cover everything. Use this information when making your treatment choices with your doctors. You should mention any worries you have. Remember that you can ask for more information at any time.



What is the problem?

You have a channel or tunnel running from inside the anus to the nearby skin. The medical name for the channel is an anal fistula. There may be more than one fistula.

Anal fistula

The fistula discharges yellow or brown liquid onto the skin. There may be attacks of pain and swelling at the skin opening and bleeding.


A fistula tracks near the anal sphincter that controls the opening of the bowel. If it runs just inside the sphincter or just through a small part of it, it is called a low fistula. If it runs from well above the sphincter, it will be right outside the sphincter and is a called a high fistula. These are important matters when treating a fistula.


What has gone wrong?

The most common cause of a low fistula is infection of a little gland just inside the anus. Instead of draining back into the anal canal, the infection burrows through the wall of the anus. It may form an abscess in the skin near the anus, called a perianal abscess. The pus may discharge through the skin.


About half of these abscesses do not heal, but go on to form a fistula. These fistulas are usually single.

Anal fistula 2

A high fistula is less common. The lining of the lower bowel may be affected by an inflammatory condition, called Crohn’s disease. Infection burrows through the wall of the bowel like a simple fistula, but usually from a much higher level. These fistulas are often multiple, complex and more difficult to treat. More rarely still, the cause of the fistula may be a bowel tumour.


Special tests, such as scans, a barium enema, x-rays and injection of x-ray liquids down the fistula may be needed to give more information about the problem.


The aims

The aims are to find the track of a low fistula, cut down onto it and allow it to heal. Imagine a tunnel being changed into a trench, by taking the roof off. The wound heals from the floor of the trench to form a flat scar, which may take several weeks.


The operation aims to avoid damage to the anal sphincter.

Anal fistula 3

A piece of the wall is taken for examination under the microscope to rule out Crohn’s disease or a tumour. You should be able to have your operation as a day case, which means you come into hospital and go home the same day.


The treatment of a high fistula aims to do the same, but is more complex, because of the anal sphincter and the underlying disease in the bowel. Sometimes it is not possible to tell before surgery the extent of the fistula and decisions are made when you are under anaesthetic.


The benefits

The discharge and bouts of pain, swelling and bleeding should stop as the fistula heals. If there is Crohn’s disease or a tumour, more treatment will be planned.


Are there any alternatives?

If you do nothing, the fistula may heal up by itself. More often, the discharge continues. Perianal abscesses may form in the same place over time.


With some very complex high fistulas, just treating the abscesses that appear from time to time may be the best treatment.


An older treatment was to pass a thread from the skin opening, through the fistula, out through the anus, and to tie the thread in a loop. The loop would pass through the tissues over several weeks. The fistula heals as the tissues also heal.


Author: Mr Michael Edwards FRCSEng FRCSEd. Consultant general surgeon.

© Dumas Ltd 2006

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