Overview & Description

A colonoscopy is a test where a flexible fiber opticinstrument is inserted into the colon, also called the large intestine.This instrument is called acolonoscope. It is a long, thin tube with a camera and light on the end.With it, a doctor can view the inner surface of the colon.The doctor can also sample or remove abnormal growthsthrough the colonoscope.

Who is a candidate for the test?

A colonoscopy may be recommended for a person with:

  • abdominal pain
  • a change in bowel habits
  • colorectal polyps,which are small growths on the intestinal wall that may lead to cancer
  • a history of colorectal cancer
  • mucus, pus, or blood in the stool
  • prolonged or unexplained diarrhea
  • ulcerative colitis
  • A colonoscopy may also be recommended for someone at highrisk for colorectal cancer.This may include a person who has a strong family history of colorectalcancer or polyps.

    How is the test performed?

    The person may be given medicine to make him or her drowsy ormore comfortable during the procedure. The person lies on one side withknees flexed toward the abdomen. The doctor inserts the colonoscopethrough the anus and up into the large intestine. The instrument is pushedthrough the colon until it comes to the place where the colon meets thesmall intestine.

    At that point, air is passed throughthe colonoscope to gently inflate the colon. This gives the doctor a clearview of the inner lining of the colon. The doctor thenwithdraws the instrument slowly, while examining all regions of the colonalong the way. Places of interest on the interior of the colon are sometimesphotographed.

    If the doctor seestissue that looks abnormal, a biopsy,which is a small tissue sample, may be taken. Small colorectal polyps can also beremoved through the colonoscope.

    Preparation & Expectations

    What is involved in preparation for the test?

    The doctor can provide instructions.Some type of bowel preparation is usually needed. The person may be asked to:

  • fast overnight before the test
  • have enemas to remove stool from the lower intestine
  • stay on a liquid diet for 1 to 3 days before the test
  • swallow a liquid that cleanses the bowel
  • Results and Values

    What do the test results mean?

    Abnormalities in the lining of the colon may indicate:

  • colorectal cancer
  • colorectal polyps
  • diverticulosis, which causes pockets in the intestinal walls
  • gastrointestinal bleeding
  • inflammatory bowel disease
  • Article type: xmedgeneral