Sometimes the symptoms of a fistula can be mistaken for the symptoms of another condition. A number of tests and investigations may be done to find out exactly what is causing the symptoms.
It’s important to know whether a fistula has developed because of a cancer that is growing, or as a result of previous treatment. This is because the way the fistula is managed will be different depending on why it has developed.
Your doctor will ask about your symptoms and talk to you about any surgery or treatment you've had in the past. They may also need to do a physical examination of the affected area. As many fistulas can develop in the pelvic area, some people feel embarrassed by this procedure. If you would prefer to be examined by a doctor of the same sex as you, just let your doctor or nurse know.
The kind of tests used will depend on the symptoms you have and the area of the body that is affected. Your doctor or nurse will explain the investigations to you and will answer any questions you have. Some of the tests that can be used are:
Methylene blue test
This is used to help diagnose a fistula involving the vagina and bowel. A tampon is placed into the vagina and then some harmless blue dye (methylene) is placed into the back passage. After about 10-15 minutes the tampon will be removed. Blue staining on the tampon shows that there is a fistula.
CT (computerised tomography) scan
A CT scan takes a series of x-rays that build up a three-dimensional picture of the inside of your body. The scan is painless but takes about 10-30 minutes. CT scans use a small amount of radiation, which will be very unlikely to harm you and will not harm anyone you come into contact with. You will be asked not to eat or drink for at least four hours before the scan. A CT scan can be used to identify a fistula and show exactly which parts of the body are affected.
MRI (magnetic resonance imaging) scan
This test is similar to a CT scan, but uses magnetism instead of x-rays to build up a detailed picture of an area of your body. During the scan you will be asked to lie very still on the couch inside a long tube for about 30 minutes. It is painless but can be uncomfortable, and some people can feel a bit claustrophobic during the scan. It is noisy, but you will be given ear plugs or headphones.
Sometimes a liquid that shows up on x-rays is used to help show the structures of the body affected by the fistula. The liquid is called a contrast medium. It can be injected into a vein in your arm or inserted into the part of the body that is affected, such as the bladder, the vagina or a fistula opening on the skin. The liquid is completely harmless.
The different types of contrast x-ray are explained below:
To help diagnose a fistula involving the bladder, the contrast medium is inserted into the bladder using a thin, rubber tube (catheter).
This test can help to show whether there is a fistula involving the vagina. A thin, rubber tube (catheter), which has a small balloon on the end, is inserted into the vagina. The balloon is then inflated to block the opening of the vagina before the contrast liquid is injected into the vagina through the catheter. X-rays of the vagina are then taken, and any leakage of the liquid will show the position and size of a fistula.
A very small catheter or blunt needle is inserted into the opening of the fistula on the skin. The contrast liquid is then injected into the fistula and x-rays are taken.
Intravenous urogram (IVU/IVP)
This test, also known as an intravenous pyelogram, can help show a fistula involving the bladder and kidneys. It is done in the hospital x-ray department and takes about an hour.
A dye is injected into a vein, usually in the arm, and flows through the bloodstream to the kidneys. The doctor can watch the passage of the dye on an x-ray screen and see any abnormalities in the kidneys, bladder and the rest of the urinary system.
The dye will probably make you feel hot and flushed for a few minutes, but this feeling gradually disappears. You may feel some discomfort in your abdomen, but this will only be for a short time. You should be able to go home as soon as the test is over.
These tests can be done to look for a fistula involving the digestive system. Barium is a substance that shows up on x-rays and can be given as a drink or in an enema. You may need to have an empty bowel before your barium x-ray so that a clear picture can be seen. Your hospital will give you instructions, but it is likely that you will be asked to take a laxative on the day before the test and to drink plenty of fluids.
Depending on which part of the body is being investigated, you'll either be given a drink of liquid containing the barium (a barium meal or swallow) or an enema of a liquid containing the barium (a barium enema). The doctor can watch the passage of the barium through your digestive system on a screen and can see any abnormalities.
Examination under anaesthetic (EUA)
This allows your doctor to carefully examine the areas affected by the fistula while you are under a general anaesthetic. The doctor can do a thorough examination without causing you any discomfort.