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Colonoscopy is a procedure that lets your doctor look inside your entire large intestine. It uses an instrument called a colonoscope, or scope for short. Scopes have a tiny camera attached to a long, thin tube. The procedure lets your doctor see things such as inflamed tissue, abnormal growths, and ulcers.

Your doctor may recommend a colonoscopy:

  • To look for early signs of cancer in the colon and rectum. It may be part of a routine screening, which usually starts at age 50.
  • To look for causes of unexplained changes in bowel habits
  • To evaluate symptoms like abdominal pain, rectal bleeding, and weight loss

Your doctor can also remove polyps from your colon during a colonoscopy.

You need to be on a clear liquid diet for 1 to 3 days before the colonoscopy. During the procedure, you receive medicines to keep you relaxed.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

  • Start Here

    • ColonoscopyFrom the National Institutes of Health(National Institute of Diabetes and Digestive and Kidney Diseases)
    • ColonoscopyInteractive Tutorial(Patient Education Institute)
    • Also available in Spanish


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Illustration of the large intestine, small intestine and rectum


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