Embarrassing Illnesses

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.