Fistula

An anal fistula usually develops after an anal abscess (a collection of pus) bursts. It can also form when an abscess has not been completely treated.

They can also be caused by a condition that affects the intestines, such as irritable bowel syndrome or Crohn’s disease.

Most anal fistulas require surgery, as they rarely heal if left untreated. However, complications are rare, and in most cases, a fistula will not develop for a second time.

Symptoms

The symptoms of an anal fistula may include:

• A throbbing, constant pain
• Irritation of skin around the anus
• Fever
• Evidence of pus or blood when passing stools, and
• Generally feeling unwell

Pain tends to worsen when you sit, move around, pass stools or cough

If a fistula has been caused by a condition which causes inflammation of the intestines, such as irritable bowel syndrome (IBS), ulcerative colitis, diverticulitis or Crohn’s disease, you may experience other symptoms such as:

• Abdominal pain
• Diarrhoea
• Loss of appetite
• Weight loss
• Nausea, and
• Vomiting

Causes

Anal abscess

Anal fistulas most commonly develop as a result of an anal abscess. An abscess is a collection of pus and infected fluid. An anal abscess normally develops after a small gland, just inside the anus, becomes infected with bacteria or foreign matter. Abscesses are usually treated with a course of antibiotics. In most cases, you will also need to have the infected fluid drained away from the abscess.

If an anal abscess bursts before it has been treated, then it can sometimes lead to an anal fistula. A fistula may also occur if an abscess has not completely healed, or if the infected fluid has not been entirely drained away.

An abscess does not always develop into a fistula. Approximately half of all people who experience an anal abscess will go on to develop a fistula. There is no way of predicting when a fistula will develop.

Anal fistulas are also a common complication of conditions that result in inflammation of the intestines. Some of these conditions include:

• Irritable bowel syndrome (IBS)
• Diverticulitis
• Ulcerative colitis
• Crohn’s disease
• Tuberculosis
• Gonorrhoea, and,
• Cancer of the rectum

Diagnosis

To make a diagnosis, your GP will look at your medical history and carry out a physical examination. Your GP will pay particular attention to any history of anal abscesses or conditions which affect your bowels, such as Crohn’s disease, as these conditions can sometimes lead to an anal fistula.

When conducting a physical examination, your GP will look closely at your anal region to see if there are physical signs of a fistula. The opening of a fistula normally appears as a red, inflamed spot, which is often oozing pus. If your GP is able to locate the opening of the fistula, they may be able to make a more accurate judgement as to where the path of the fistula lies. Sometimes the path of the fistula can be felt as a hard, cord-like structure beneath the skin.

In many cases, you may have to have further testing carried out so that a more detailed look at the fistula can take place. Your doctor may use the following instruments to carry out further investigation:

• Fistula probe: A fine, narrow instrument which is specifically designed to be inserted though a fistula
• Anoscope: This instrument is lubricated and is passed a few inches into your rectum (the last part of the large intestine which stores solid waste). An anoscope has a light on the end, which allows the person using it to see the entire anal canal. It is also able to take small tissue samples.

If your fistula is in a complicated or unusual position, your doctor may also have to carry out further tests, which may include:

• Diluted methylene blue dye: This dye is injected into the fistula and it helps to show your doctor the fistula’s position and path. The dye very rarely causes any side effects.
• Fistulography: This involves having a special solution injected into your fistula. You will then have an x-ray, which shows the path of the solution as an x- ray image.
• Magnetic resonance imaging (MRI) scan: This scan uses magnetic and radio waves to produce detailed images of the inside of your body. This type of scan will help pinpoint the size and route of a fistula.

Treatment

The main aim of treatment for an anal fistula is to heal the fistula with as little effect on the anal sphincter muscles (the ring of muscles that open and close the anus) as possible. Damage to the sphincter muscles could cause incontinence problems in the future.

Very few anal fistulas are able to heal by themselves, so surgery is usually necessary.

Fistulotomy

The main surgical procedure used to treat a fistula is a fistulotomy. During this procedure, the surgeon will cut open the fistula, whilst you are under general anesthetic, and then scrape and flush out its contents. The fistula is then laid open and flattened out. After 1-2 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.

If the fistula is relatively simple to operate on, you may have the surgery and go home the same day. If the path of the fistula is particularly long or complicated, you may need to stay in the hospital for a few days, or undergo a second stage of surgery to complete the procedure.

It can be painful to move around soon after the operation, but after approximately one week, any pain and discomfort should ease. Most people make a full recovery after two to six weeks, but if the fistula was particularly complicated, it can take up to eight weeks for it to heal completely.

Fibrin glue or collagen plug

Most cases of anal fistula will require surgery, However, in some cases, you may be able to have the fistula sealed with a special type of glue made from protein. This means the fistula will not have to be cut open. The glue is injected through the opening of the fistula and then stitched closed. A fistula can also be sealed using a small plug made of collagen and then stitched closed.

Complications

Infection

An anal fistula rarely causes any further complications. There is approximately a one in ten chance of a fistula recurring, but with proper treatment and care, a fistula will not normally return. If complications do develop, they are usually the result of fistula surgery.

Any type of surgery carries a risk of infection, and if the fistula is not completely treated during surgery, it can sometimes cause the infection in the tract to spread to other parts of the body. If this happens you may require a course of antibiotics. If the infection is severe, you may need to be admitted to the hospital so that antibiotics can be administered intravenously (through a drip in your arm).

Sphincter muscle damage

In some rare cases, surgery may damager the anal sphincter muscles (the ring of muscles that open and close the anus). If the muscles are damaged, this can lead to you losing some control of your bowels (faecal incontinence). If you already have some faecal incontinence, you may find that this worsens after fistula surgery.