General Information:

  • Description: A long, flexible tube with a camera mounted on the end (colonoscope) is inserted into the rectum and guided to the end of the colon (large intestines). This allows for viewing the internal lining of the colon directly. A gastroenterologist performs the test with assistance from a nurse in a hospital, endoscopy suite, or doctor’s office. The gastroenterologist interprets the results. If specimens are obtained, a pathologist interprets the results. The test takes 15-60 minutes to complete. 
  • Discomfort: An intravenous line has to be placed. Depending on the level of sedation, there may be some discomfort as the scope is passed through the colon and as air is instilled into the intestines.
  • Results: The Gastroenterologist’s interpretation is available immediately; 2-3 days for results from tissue samples obtained. 
  • Risks of Procedure: Colon perforation is the major risk and occurs in 0.01% to 0.5% of cases. Other risks include bleeding, infection, and adverse reaction to the medication used for sedation.
  • Other Names: Lower Endoscopy

Indications for the Test:

  • Colon cancer and colon polyp screening
  • To further evaluate abnormalities identified in the colon by other tests 
  • To identify a source of diarrhea, bleeding, or anemia (low blood count) 


  • Only clear liquids are consumed on the day before the test. After midnight on the morning of the test, nothing should be consumed, except medications as directed by your doctor.
  • A special medication (laxative) will be given the day before the test with instructions on how to take it. An enema may be prescribed on the morning of the test. It is important that the laxative be taken as prescribed in order for the colon to be cleaned adequately.
  • Aspirin, non-steroidal anti-inflammatory drugs (aspirin substitutes), blood thinners, anticoagulants, and iron supplements should not be taken for five days before the test to reduce the risk of bleeding.
  • If the procedure is performed on an outpatient basis, patient must arrange in advance to have someone drive them home afterward.
  • Patient will be asked to remove all clothing and wear a hospital gown.
  • If patient is at a high risk of certain types of heart disease, they may be given antibiotics to prevent infection, since there is a small risk that infectious organisms from the bowels may penetrate the bloodstream as a result of this procedure and may travel to the heart. 


  • After changing into a hospital gown, you will have an intravenous line placed for the sedative to be given.
  • Monitors are attached to observe the blood pressure, pulse rate, and oxygen level of the blood. Supplemental oxygen is given via the nose.
  • While lying on your left side, you are sedated. The doctor examines the colonic lining as it is projected to a TV monitor as the scope is guided into the colon. Air is instilled into the colon to aid in visualization of the lining.
  • If indicated by the findings, the doctor can take tissue samples, treat sites that are bleeding, place stents, or remove polyps (growths).
  • During the test, you may have discomfort related to a feeling of distention. Breathing slowly and deeply usually relieves this discomfort. 

After the Procedure:

  • You are monitored in the recovery area until the sedation wears off.
  • Once the sedation wears off, you may have someone drive you home.
  • You pass large amounts of gas for several hours after the test.
  • You may be advised not to take aspirin or aspirin substitutes for up to 2 weeks after the test. 
  • Notify your doctor immediately if you experience bleeding, severe pain, or fever after the test.

Factors Affecting Results:

  • An incomplete bowel preparation will obscure the lining of the colon, limiting the doctor’s ability to examine the colon.


  • The lining of the colon can be viewed directly. 
  • Abnormalities identified can be biopsied and polyps can be removed during the test. 


  • The preparation for the test is unpleasant.
  • There may be some discomfort during the test.
  • The test is invasive.
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