DEAR DOCTOR K:

My brother was recently diagnosed with colon cancer. Now my doctor wants me to have a colonoscopy. Can you tell me what will happen during this procedure?

DEAR READER:

Your brother's diagnosis puts you at higher risk for colon cancer, so I'm glad to hear your doctor has recommended that you get checked.

Colonoscopy is used to look at the lining of your colon, or large intestine. The procedure can detect colon cancer, as well as abnormal growths (polyps), inflammation, bleeding, weaknesses in the wall of the intestine (diverticular disease) and other problems of the digestive tract.

Your bowel needs to be empty during the colonoscopy to give your doctor a clear view of your intestine. Your doctor may ask you to have a liquid diet the afternoon and evening before the test, and to eat nothing the night before the procedure. To help empty your bowel, your doctor will ask you to drink a lot of fluid, with laxatives in it, the day before the procedure. This is the part of the procedure that makes you "go" a lot.

Many people find "the cleanout" to be the unpleasant part of the procedure. I've had two colonoscopies myself, and that's surely my view. As far as I'm concerned, anyone who can invent a way of cleaning out the bowels without the use of laxatives should get the Nobel Prize.

For the procedure itself, you will be asked to lie on your side on an examination table. The lower part of your body will be covered by a sheet.

Your doctor will use an instrument called a colonoscope. This is a flexible viewing tube with lenses, a small TV camera and a light on one end. The colonoscope scans the inside of your colon and transmits images to a video screen.

The colonoscope is lubricated and bends easily. You will be given light doses of sedatives to minimize any discomfort. The sedatives can create a sort of "dreamy" feeling. In fact, you may not remember much about the procedure after it's over.

Your doctor will insert the colonoscope into your rectum and, as necessary, pump a small amount of air through the colonoscope. The air will open up your intestine for a clearer view. You may be asked to raise one or both of your knees up to your chest.

If your doctor sees a suspicious area during colonoscopy, he can take a small tissue sample to be examined in a laboratory. If a polyp is found during colonoscopy, your doctor may remove it.

The procedure can take up to an hour. Afterward, you may still feel drowsy from the medication. You need to arrange for a friend or family member to help you get home: In most states, the doctor is not allowed to let you walk or drive yourself home, or even to take a taxi. Either the doctor performing the test or your primary care doctor will tell you the results.

Even though it has its unpleasant aspects, a colonoscopy is a miraculous advance. It can see inside your colon, catch colon cancer early and save your life.

(Dr. Komaroff is a physician and professor at Harvard Medical School. Go to his website to send questions and get additional information: www.AskDoctorK.com.)

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