A colonoscopy is a way of examining the lining of the bowel from the inside. The procedure is usually done in the hospital outpatient department and takes about an hour. It's the most thorough and effective way of diagnosing bowel cancer. The colonoscopy can also see if there are any polyps in your bowel.
The bowel has to be completely empty for a colonoscopy. This means following a careful diet for a few days before your test. You'll also need to take laxatives, which the screening centre or hospital pharmacy will provide. The department carrying out your colonoscopy will give you instructions about your diet, and about exactly when to take your laxatives.
Shortly before the colonoscopy, you may be given a sedative to help you feel relaxed. Once you're lying comfortably on your side, the nurse or doctor will gently pass a thin flexible tube (a colonoscope) into your back passage. The tube is made up of flexible fibres so it can easily pass around the curves of the bowel. A tiny light and camera on the end of the tube are used to show any abnormal areas.
During the colonoscopy, photographs and samples (biopsies) of the cells on the inside of the large bowel can be taken. Most polyps can be painlessly removed using a wire loop that is passed down the colonoscope. A colonoscopy can be uncomfortable, but the sedative will help you feel more relaxed.
Most people are ready to go home a couple of hours after their test. You'll need to arrange for someone to collect you from the hospital as you shouldn't drive for several hours after a sedative. You should also have someone with you for about 12 hours afterwards.
Sometimes it's not possible to see the whole bowel during a colonoscopy. This can happen if the bowel isn't completely empty or if the colonoscope can't pass round a bend in the bowel to reach the end. If this happens, you may be asked to have another colonoscopy, or a CT colonogram.