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Colonoscopy is a test to view the inside of your lower digestive tract (colon and rectum). Sometimes it can show the last part of the small intestine (ileum). During the test, small pieces of tissue may be removed for testing. This is called a biopsy. Small growths, such as polyps, may also be removed. 

Doctor and technician performing colonoscopy on patient lying on side.
A camera attached to a flexible tube with a viewing lens is used to take video pictures.

Why is colonoscopy done?

The test is done to help look for colon cancer. And it can help find the source of abdominal pain, bleeding, and changes in bowel habits. It may be needed once a year to every 10 years, depending on factors such as your:

  • Age

  • Health history

  • Family health history

  • Symptoms

  • Results from any prior colonoscopy

Risks and possible complications

These include:

  • Bleeding             

  • A puncture or tear in the colon 

  • Risks of anesthesia

  • A cancer lesion not being seen or fully removed

Getting ready 

To prepare for the test:

  • Talk with your healthcare provider about the risks of the test (see below). Also ask your healthcare provider about alternatives to the test.

  • Tell your healthcare provider about any medicines and supplements you take. Also tell him or her about any health conditions you may have.

  • Make sure your rectum and colon are empty for the test. Follow the diet and bowel prep instructions exactly. If you don’t, the test may need to be rescheduled.

  • Plan for a friend or family member to drive you home after the test.


You may discuss the results with your doctor right away or at a future visit.

During the test 

The test is usually done in the hospital on an outpatient basis or at an outpatient clinic. This means you go home the same day. The procedure takes about 30 minutes. During that time:

  • You are given relaxing (sedating) medicine through an IV line. You may be drowsy, or fully asleep.

  • The healthcare provider will first give you a physical exam to check for anal and rectal problems.

  • Then the anus is lubricated and the scope inserted.

  • If you are awake, you may have a feeling similar to needing to have a bowel movement. You may also feel pressure as air is pumped into the colon. It’s OK to pass gas during the procedure.

  • Biopsy, polyp removal, or other treatments may be done during the test.

After the test 

You may have gas right after the test. It can help to try to pass it to help prevent later bloating. Your healthcare provider may discuss the results with you right away. Or you may need to schedule a follow-up visit to talk about the results. After the test, you can go back to your normal eating and other activities. You may be tired from the sedation and need to rest for a few hours. Discuss your medicines with your provider to understand if they can be restarted right away.

When to call your healthcare provider

Call your healthcare provider if you have any of the following after the procedure:

  • Pain in your belly

  • Fever of 100.4°F (38°C) or higher, or as directed by your provider

  • Rectal bleeding

  • Nausea or vomiting

Online Medical Reviewer: Jen Lehrer MD
Online Medical Reviewer: L Renee Watson MSN RN
Online Medical Reviewer: Ronald Karlin MD
Date Last Reviewed: 6/1/2019
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