Healthcare worker with anatomical demonstration tool

Colonoscopy

Colonoscopy lets the physician look inside your entire large intestine, from the lowest part, the rectum, all the way up through the colon to the lower end of the small intestine. The procedure is used to diagnose the causes of unexplained changes in bowel habits. It is also used to look for early signs of cancer in the colon and rectum. Colonoscopy enables the physician to see inflamed tissue, abnormal growths, ulcers, bleeding, and muscle spasms.

The Process

  • For the procedure, you will lie on your left side on the examining table.
  • You will probably be given pain medication and a mild sedative to keep you comfortable and to help you relax during the exam.
  • The physician will insert a long, flexible, lighted tube into your rectum and slowly guide it into your colon. The tube is called a colonoscope.
  • The scope transmits an image of the inside of the colon so the physician can carefully examine the lining of the colon.
  • The scope bends so the physician can move it around the curves of your colon.
  • You may be asked to change position occasionally to help the physician move the scope.
  • The scope also blows air into your colon, which inflates the colon and helps the physician see better.
  • If anything unusual is in your colon, like a polyp or inflamed tissue, the physician can remove a piece of it using tiny instruments passed through the scope.
  • That tissue (biopsy) is then sent to a lab for testing.
  • If there is bleeding in the colon, the physician can pass a laser, heater probe, or electrical probe, or inject special medicines, through the scope and use it to stop the bleeding.
  • Bleeding and puncture of the colon are possible complications of the colonoscopy. However, such complications are uncommon.
  • Colonoscopy takes 30 to 60 minutes.
  • The sedative and pain medicine should keep you from feeling much discomfort during the exam.
  • You will need to remain in the recovery room for at least 30 minutes until the sedative wears off.
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Stomach ulcer illustration with highlighted area
Doctor using an endoscopic device

Preparation

Your colon must be completely empty for the colonoscopy to be thorough and safe. To prepare for the procedure, you may have to follow a liquid diet for 1 to 3 days beforehand. A liquid diet means fat-free bouillon or broth, Jell-O, strained fruit juice, water, plain coffee, plain tea, or diet soda. You may need to take laxatives or an enema before the procedure. Also, you must arrange for someone to take you home afterward—you will not be allowed to drive because of the sedatives. Your physician may give you other special instructions.

This information has been prepared by the National Digestive Diseases Information Clearinghouse, a service of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Public Health Service.