Colonoscopy: examination of the colon
What is a colonoscopy?
A colonoscopy is an examination of the lower digestive tract or colon, using a colonoscope — a long, thin, flexible tube containing a camera and a light — to view the lining of the bowel. A colonoscope is a type of endoscope.
Why is this test done?
A colonoscopy is usually performed to investigate any recent changes in bowel habits, bleeding from the rectum (back passage), abdominal pain or prolonged diarrhoea, and to screen for early signs of bowel cancer. It is done to make or confirm a diagnosis.
What do I need to do to prepare for a colonoscopy?
You will usually be given a preparation kit with full instructions. This usually means having a special diet for a couple of days, and nothing but clear fluids for 24 hours before the test. You will usually be asked to take a laxative to clean out the bowel and some people may require an enema if they have been constipated. Before the colonoscopy, the doctor will discuss the test with you and answer any questions, and then you will be asked to sign a consent form allowing the test to be done.
What happens during a colonoscopy?
You may be asked to change into a hospital gown and lie on the table on your left side, with your knees pulled up. Usually you will have a needle inserted into your hand and a light sedative will be given. This will help you to relax, and may put you to sleep. Generally, you will have no recollection of the procedure.
The doctor will lubricate your rectal opening, then the scope will be inserted and gently guided along the bowel until it reaches an area near the appendix. Air will be pumped in, to make it easier to see the bowel lining and pass the scope.
Sometimes a special instrument can be inserted through the scope, and a small piece of tissue (a biopsy) or a polyp (a small, usually benign, growth) can be removed from the wall of the bowel and sent to the laboratory for examination. Both of these things are usually painless. The doctor may also take some pictures to refer to later. Once the doctor is happy that everything has been seen, the scope will be removed. The procedure usually takes between 20 and 45 minutes.
What happens after a colonoscopy?
You will be taken to a recovery room to rest for about 2 hours while the sedative starts to wear off. You will probably be allowed to go home after this time, but you will need to have a friend or relative drive you home. You should not drive or operate machinery until the next day.
Your doctor may briefly run through the test results with you when you wake up, but a follow-up appointment is recommended to discuss the findings more fully.
What are the risks?
Most people experience no serious side effects from a colonoscopy. You may experience some pain in the abdomen from the air that was pumped in and you will be passing wind for a day or 2. Some minor bleeding may occur, especially if a biopsy was taken or a polyp removed. Some people may not tolerate the preparation, or have a reaction to the sedative.
Very rarely, major bleeding or a bowel perforation (a tear in the bowel wall) may occur. In such cases, you would be admitted to hospital and may need a blood transfusion or an operation to repair any damage to the bowel wall.
Further information and support
Talk to your doctor. Contact the hospital or centre where you are having the colonoscopy.
Last Reviewed: 25 November 2009
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