A colonoscopy is an internal examination of the colon (large intestine) and rectum, using an instrument called a colonoscope.
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.
Specialized procedures, such as laser therapy, may also be done.
You will need to completely cleanse your intestines. Your health care provider will give you instructions for doing this. This may include a combination of enemas, not eating solid foods for 2 or 3 days before the test, and taking laxatives. You will usually be told to stop taking aspirin, ibuprofen, naproxen, or other blood-thinning medications for several days before the test.
You will be asked to drink plenty of clear liquids for 1 - 3 days before the test. Examples of clear liquids are:
Unless otherwise instructed, continue taking any regularly prescribed medication. Stop taking iron medications a few weeks before the test, unless your health care provider tells you otherwise. Iron can produce a dark black stool, which makes the view inside the bowel less clear.
Outpatients must plan to have someone take them home after the test, because they will be woozy and unable to drive.
Infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:
The sedative and pain medication will relax you and make you feel drowsy. Many patients do not remember having the colonoscopy. A rectal examination usually is done before the test to make sure there are no major blockages. You may have the urge to have a bowel movement when the rectal exam is performed or as the colonoscope is inserted.
You may feel pressure as the scope moves inside. You may feel brief cramping and gas pains as air is inserted or the scope advances. Passing gas is necessary and should be expected.
You can reduce discomfort by taking slow, deep breaths. This will also help relax your abdominal muscles. You may have mild abdominal cramping and pass a lot of gas after the exam. 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.
Colonoscopy may be used for the following reasons:
Normal findings are healthy intestinal tissues.
Additional conditions under which the test may be performed:
You must sign an informed consent form. Several hours of rest is recommended after the test. To replace fluids lost because of laxatives and fasting, drink plenty of liquids after the test.
Kimmey MB. Complications of gastrointestinal endoscopy. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier;2010:chap 40.
Pasricha PJ. Gastrointestinal endoscopy. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 136.
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