Definition Of Colonoscopy

A colonoscopy is an internal examination of the colon (large intestine) and rectum, using an instrument called a colonoscope.

How The Test Is Performed

The colonoscope has a small camera attached to a flexible tube. Unlike sigmoidoscopy, which can only reach the lower third of the colon, colonoscopy examines the entire length of the colon.

You will lie on your left side with your knees drawn up toward your chest. After you have received a sedative and pain reliever, the colonoscope is inserted through the anus. It is gently moved into the beginning of the large bowel and sometimes into the lowest part of the small intestine.

Air will be inserted through the scope to provide a better view. Suction may be used to remove fluid or stool.

Because the health care provider gets a better view as the colonoscope is pulled back out, a more careful examination is done while the scope is being pulled out. Tissue samples may be taken with tiny biopsy forceps inserted through the scope. Polyps may be removed with electrocautery snares, and photographs may be taken.

How To Prepare For The Test

You will need to completely cleanse your intestines. This may include a combination of enemas, not eating solid foods for 2 or 3 days before the test, and taking laxatives.You will be asked to drink plenty of clear liquids for 1 – 3 days before the test.Otherwise instructed, continue taking any regularly prescribed medication. Stop taking iron medications a few weeks before the test.

Outpatients must plan to have someone take them home after the test, because they will be woozy and unable to drive.

How The Test Will Feel

The sedative and pain medication will relax you and make you feel drowsy. A rectal examination usually is done before the test to make sure there are no major blockages.

Sedation should wear off in a few hours. Because of the sedation, you may not feel any discomfort and may have no memory of the test.

Why The Test Is Performed

  • Abdominal pain, changes in bowel movements, or weight loss
  • Abnormal changes (such as polyps) found on sigmoidoscopy or x-ray tests ( CT scan or barium enema)
  • Anemia due to low iron (usually when no other cause has been found)
  • Blood in the stool, or black, tarry stools
  • Follow-up of a past finding, such as polyps or colon cancer
  • Inflammatory bowel disease (ulcerative colitis and Crohn’s disease)
  • Screening for colorectal cancer