During a colonoscopy, your doctor uses a thin, flexible camera to detect abnormalities or disease in the colon. The colon is the lowest part of the gastrointestinal tract that absorbs food, nutrients and eliminates waste. The colon is attached to the anus via the rectum. Your doctor may also take tissue samples for a biopsy. This allows them to remove abnormal tissue such as polyps.

In what cases is this procedure performed?

A colonoscopy can be used to screen for colon cancer and other problems. Screening can help your doctor to:

• Look for signs of cancer and other problems
• Explore the cause of unexplained changes in bowel habits
• Assess symptoms of pain or bleeding in the abdominal area
• Find a reason for weight loss, chronic constipation or diarrhea

Anyone older than 50 years with an average risk of colon cancer should have a colonoscopy once every 10 years. If you are at increased risk, you may need more frequent procedures. It is estimated that 76-90% of colon cancers can be prevented through colonoscopy screening.

The risks of a colonoscopy

Because a colonoscopy is a routine procedure, this test usually has little lasting effect. In the vast majority of cases, the benefits of detecting problems and starting treatment far outweigh the risks of complications from a colonoscopy.

However, some rare complications include:

• Bleeding from a biopsy site if a biopsy has been performed
• A reaction to the sedative
• A tear in the rectal or colonic wall

How to prepare for this medical examination?

Your doctor will explain how to do a "bowel prep". You must be on a clear liquid diet for 24 to 72 hours before your procedure. The typical gut preparation regimen includes:

• Broth
• Gelatin
• Regular coffee or tea
• Juice without pulp
• Sports drinks

Be careful not to drink liquids that contain red or purple dye, as they can discolor your colon.

Tell your doctor about all the medications you are taking, including over-the-counter medications or supplements. If they can affect your colonoscopy, your doctor may ask you to stop taking them. These may include blood thinners, iron-containing vitamins, and some anti diabetes.

Your doctor may prescribe a laxative to take the night before your appointment. He or she will probably advise you to use an enema to clean out your colon on the day of the procedure.

How is a colonoscopy performed?

Just before the procedure, you will put on a hospital gown. Most people take a sedative, usually in pill form.

During the procedure, you will lie on a padded examination table. Your doctor may position you with your knees close to your chest to get a better angle with your colon.

While you are under sedation, your doctor will insert a flexible, lighted tube called a colonoscope into your anus. It will guide it through the rectum and into the colon. A camera at the end of the colonoscope transmits images to a monitor that your doctor will watch.

Once the scope is placed, your doctor will inflate your colon with carbon dioxide. It gives them a better view.

Your doctor may remove polyps or a tissue sample for biopsy during this procedure. You will be awake during your colonoscopy so that your doctor can tell you what is going on.

The whole procedure takes about 40 minutes to an hour.

After a colonoscopy

Once the procedure is complete, you wait about an hour to allow the sedative to wear off. You will be advised not to drive for the next 24 hours until its effects wear off.

In addition, your doctor will probably inject you with gas and bloating. If this continues for days, it may mean a problem and you should contact your doctor.

Also, a little blood in your stool after the procedure is normal. However, call your doctor if you continue to have blood or blood clots. If you have abdominal pain or a fever over 30°C, see your doctor as well.

In the event that your doctor removes a tissue or polyp during a biopsy, he or she will send it to a laboratory for testing. Your doctor will tell you the results when they are ready, which is usually within a few days.

Foods you can eat after a colonoscopy

After a colonoscopy, you should eat or drink foods that are gentle on your digestive system. Drinking plenty of fluids and fluid-based foods will help you avoid dehydration.

Your doctor may recommend that you follow a gentle, low-residue diet immediately after the procedure. This consists of a limited amount of dairy products, as well as foods that are low in fiber, easy to digest and produce less stool.

Foods and drinks to have the day after your colonoscopy are:

• Drinks with electrolytes
• Water
• Fruit juice
• Vegetable juice
• Herbal tea
• Savoury cookies
• Soup
• Applesauce
• Scrambled eggs
• Tender, cooked vegetables
• Canned fruit, such as peaches
• Yogurt
• Popsicles
• Pudding
• Mashed or baked potato
• White bread or toast
• Smooth nut butter
• Soft white fish
• Apple butter

Sources

Colonoscopy. (November 2014)
digestive.niddk.nih.gov/ddiseases/pubs/colonoscopy/

Colonoscopy. (2014, November)
facs.org/public_info/operation/brochures/colonoscopy.pdf