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In this procedure, a flexible fibre optic instrument called a colonoscope is inserted into the large intestine, or colon. The colonoscope permits the doctor to view the details of the inner surface of the colon. This helps detect any abnormal tissues or growths. The doctor can also sample or remove abnormal growths through the colonoscope.

Who is a candidate for the test?
A colonoscopy may be recommended for a person with:
  • prolonged or unexplained diarrhoea.
  • blood, pus or mucous in the stool.
  • abdominal pain of unknown aetiology.
  • a change in bowel habits.
  • a high risk for bowel cancer. This may include a strong family history for bowel cancer, polyps or ulcerative colitis.
  • a history of bowel cancer, to monitor for any new lesions.
  • unexplained anaemia or weight loss
How is the test performed?
Before the test, the doctor may give the person medication to make him or her drowsy or more comfortable during the procedure. The person lies on one side with knees flexed toward the abdomen. The doctor inserts the colonoscope through the anus and into the large intestine. The instrument is advanced through the bowel until it comes to the place where the bowel meets the small intestine. At that point, air is passed through the colonoscope to gently inflate the bowel. This gives the doctor a clear view of all aspects of the inner lining of the bowel. The doctor then slowly withdraws the instrument, examining all regions of the bowel along the way. Places of interest on the interior of the bowel are sometimes photographed. If the doctor sees tissue that looks abnormal, a biopsy may be taken as well. The removal of small growths, or polyps, and laser treatment may also be performed during colonoscopy.

What is involved in preparation for the test?
Individuals should check with their doctors for specific instructions on how to prepare for this test. Some type of bowel preparation is usually needed. This may involve the use of enemas, or drinking a liquid that helps to cleanse the bowel before the procedure.

What do the test results mean?
The inner lining may have a healthy appearance.

Abnormalities seen in the lining of the large bowel may indicate:
  • bleeding in the lower gastrointestinal (GI) tract
  • polyps
  • tumour
  • inflammatory bowel disease (inflammation and damage of the walls of the intestines)
  • diverticulosis, which are pockets in the walls of the intestines that sometimes bleed or get infected
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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