What Is a Colonoscopy?

During a colonoscopy, your doctor uses a thin, flexible camera to check for abnormalities or disease in your lower intestine or colon.

The colon is the lowest portion of the gastrointestinal tract that takes in food, absorbs nutrients, and disposes of waste. The colon is attached to the anus via the rectum. The anus is the opening in your body where feces are expelled.

During a colonoscopy, your doctor may also take tissue samples for biopsy. They may also remove abnormal tissue such as polyps.

A colonoscopy can be done as a screening for colon cancer and other problems. The screening can help your doctor:

  • look for signs of cancers and other problems
  • explore the cause of unexplained changes in bowel habits
  • evaluate symptoms of pain or bleeding located in the abdominal area
  • find a reason for weight loss, chronic constipation, or diarrhea

Everyone over the age of 50 who is at average risk of colon cancer should get a colonoscopy once every 10 years. If you’re at an increased risk, you may need more frequent procedures. The American College of Surgeons estimates that between 76 and 90 percent of colon cancer can be prevented through colonoscopy screening.

Since a colonoscopy is a routine procedure, there are typically few lasting effects from this test. In the vast majority of cases, the benefits of detecting problems and beginning treatment far outweigh the risks of complications from a colonoscopy.

However, some rare complications include:

  • bleeding from a biopsy site if a biopsy was done
  • a reaction to the sedative
  • a tear in the rectal wall or colon

Your doctor will give you instructions for a “bowel prep.” You must have a clear liquid diet for 24 to 72 hours before your procedure. The typical bowel prep diet includes:

  • bouillon or broth
  • gelatin
  • plain coffee or tea
  • pulp-free juice
  • sports drinks, such as Gatorade

Make sure not to drink any liquids containing red or purple dye because they can discolor your colon.

Tell your doctor about any medications you’re taking, including over-the-counter drugs or supplements. If they can affect your colonoscopy, your doctor may tell you to stop taking them. These might include blood thinners, vitamins that contain iron, and certain diabetes medications.

Your doctor may give you a laxative to take the night before your appointment. They’ll likely advise you to use an enema to flush out your colon the day of the procedure.

You may want to arrange for a ride home after your appointment. The sedative you’ll be given for the procedure makes it unsafe for you to drive yourself.

Just before your colonoscopy, you’ll change into a hospital gown. Most people get a sedative, usually in pill form.

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

While you’re on your side and sedated, your doctor will guide a flexible, lighted tube called a colonoscope into your anus. Slowly and gently, they’ll guide it up through the rectum and into the colon. A camera on the end of the colonoscope transmits images to a monitor that your doctor will be watching.

Once the scope is positioned, your doctor will inflate your colon using carbon dioxide gas. This gives them a better view.

Your doctor may remove polyps or a tissue sample for biopsy during this procedure. You’ll be awake during your colonoscopy, so your doctor will be able to tell you what’s happening.

The entire procedure takes about 40 minutes to an hour.

After the procedure is done, you’ll wait for about an hour to allow the sedative wear off. You’ll be advised not to drive for the next 24 hours, until its full effects fade.

In addition, you’ll likely have some gas and bloating from the gas your doctor placed into your colon. Give this time to get out of your system. If it continues for days after, it could mean there’s a problem and you should contact your doctor.

Also, a little bit of blood in your stool after the procedure is normal. However, call your doctor if you continue to pass blood or blood clots, experience abdominal pain, or have a fever over 100°F.

If your doctor removes tissue or a polyp during a biopsy, they’ll send it to a laboratory for testing. Your doctor will tell you the results when they’re ready, which is normally within a few days.