Colonoscopy

A colonoscopy allows the specialist (usually called a gastroenterologist) to examine the lining of the bowel wall, from the lowest part, the rectum, all the way up through the colon to the lower end of the small intestine. The procedure is used to diagnose the causes of unexplained changes in bowel habits. It is also used to look for the early signs of cancer in the large bowel and rectum. A colonoscopy enables the specialist to see inflamed tissue, abnormal growths, ulcers, bleeding and muscle spasms.

For the procedure, you will lie on your left side on the examining table. You will probably be given pain medication and a mild sedative to keep you comfortable and to help you relax during the examination. Your specialist will then insert a long, flexible tube with a light at the tip into your rectum and slowly guide it into your bowel. The instrument is called a colonoscope. The instrument transmits an image of the inside of the colon onto a television or computer monitor, so the specialist can carefully examine the lining of the bowel. The instrument is flexible, so the specialist can advance it around the curves of your bowel. You may be asked to change position occasionally to help the specialist move the colonoscope. The doctor may also blow air into your bowel, to inflate it and so help with visualisation. This may result in some degree of temporary discomfort.

If anything unusual is found, such as a polyp or inflamed tissue, the specialist can remove a small piece of it using tiny instruments passed through the colonoscope. That piece of tissue (a biopsy) is then sent to a laboratory for testing. If there is bleeding in the bowel, the specialist can pass a laser, heater probe or electrical probe, or inject special medicines through the instrument to stop the bleeding.

Bleeding and puncture of the bowel are possible complications of colonoscopy. However, these problems are very rare, occurring in only about one in 1,500 cases.

A colonoscopy takes 30 to 45 minutes. The sedative and pain medicine should prevent you from feeling much discomfort during the examination. You will need to remain at the hospital or medical centre for one to two hours until the sedative wears off.

Preparation for a colonoscopy

Your colon must be completely empty for the colonoscopy to be thorough and safe. To prepare for the procedure you may have to follow a liquid diet for one to three days beforehand. A liquid diet can include fat-free bouillon or broth, strained fruit juice, water, black coffee and black tea. You will usually also be given a bowel preparation medication (a strong laxative) to help empty the gut before the procedure. In addition, you must arrange for someone to take you home afterwards -- you will not be allowed to drive because of the sedatives. Your specialist may give you other instructions to follow, and you also usually receive a written advice sheet.