Colonoscopy

Doctors use the colonoscopy procedure to look for abnormalities or changes in the lower part of your digestive tract, such as the rectum and large intestine (colon).

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What is a colonoscopy?

Colonoscopy uses a tiny video camera on the end of a long, flexible tube. During the procedure, the tube is inserted into the rectum, which provides a video image of the inside of your entire colon.

If the doctor performing the colonoscopy sees anything unusual, such as a polyp or other abnormal tissue, it can be sampled for analysis and often removed through the scope.

You may be referred for a colonoscopy to:

  • Discover the source of symptoms. If you are having symptoms such as abdominal pain, chronic constipation, rectal bleeding, chronic diarrhea and other intestinal issues, your doctor may suggest a colonoscopy to see if there's anything abnormal in your colon that could be causing them.
  • Screen for cancer. Depending on your age and risk factors, your doctor may refer you for colonoscopy to screen for colon cancer. Until recently, U.S. guidelines recommended a colonoscopy every 10 years for people age 50 or older who have an average risk of colon cancer. However, new recommendations advise screenings start at age 45. If you are at higher risk, such as a family history of colon cancer, your doctor may suggest more frequent screening.
  • Reexamine the colon. If you have had polyps in the past or another abnormality, your doctor may suggest another colonoscopy to reexamine your colon and remove any additional polyps. Removing polyps helps reduce your risk of colon cancer.

What can I eat before a colonoscopy?

Colonoscopy prep starts with emptying your colon, as any food residue or debris can create problems viewing the walls of the colon and rectum. There are a few ways to empty your colon. Your doctor will talk to you about the best method that works for you. The process includes:

  • Following a prescribed diet 24 hours before the exam. Usually, the day before your colonoscopy you won't be able to eat solid food, such as chocolate or crisps. You can typically drink clear liquids, such as water, broth, tea and coffee (no milk or cream), and carbonated beverages. You'll want to avoid red liquids as they can look like blood to the camera. Depending on your circumstances, you might not be able to eat or drink anything after midnight the night before the exam.
  • Use laxatives. To empty your colon, your doctor will probably ask you to take a laxative. Depending on your circumstances, you might need to take it just the night before or the night before and the morning of your procedure.

Depending on your situation, you may need to adjust your medications. At least a week before your colonoscopy, talk to your doctor about your medications. This is especially important if you take blood-thinning medications or have a condition such as high blood pressure, heart problems or diabetes, or if you take medications or supplements that contain iron. To ensure the best image possible, you may be asked to adjust a dose or even temporarily stop a medication.

If you are worried about your medications, one of our staff will be happy to advise you when you set up your appointment.

Is a colonoscopy painful?

A colonoscopy is not usually painful. However, for most people, sedation during colonoscopy is recommended. This will usually be a sedative combined with pain medication given intravenously.

The procedure generally requires wearing a gown with nothing else. The exam begins with you lying on your side with knees drawn up as the doctor inserts the colonoscope into the rectum.

Besides containing the camera, the scope has a light and tube that inflates the colon with air, carbon dioxide or even sterile water, giving the doctor a better view of the colon lining. During the procedure, you may feel cramping or feel the need to have a bowel movement. The doctor can also pass instruments through the tube to remove polyps or take tissue samples.

How long does a colonoscopy take?

A colonoscopy usually takes between 30 and 60 minutes.

Usually it takes about an hour for the sedative to start wearing off. However, its effects can last a full day, so it is important for your safety that you have someone take you home. You won't be able to drive and shouldn't make important decisions or go back to work for the rest of the day.

Because the procedure pumps air into the colon, you may feel bloated for a few hours after the exam and pass gas. Walking can help lessen discomfort.

Mayo Clinic Healthcare will work with you to determine if a colonoscopy is appropriate to your needs.

Read more about colonoscopy on MayoClinic.org