A colonoscopy is an exam that views the inside of the colon (large intestine) and rectum, using a tool called a colonoscope.
The colonoscope has a small camera attached to a flexible tube that can reach the length of the colon.
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How the Test is Performed
Colonoscopy is done most often in a procedure room at your doctor's office. It can also be done in the outpatient department of a hospital or medical center.
How to Prepare for the Test
Your bowel needs to be completely empty and clean for the exam. A problem in your large intestine that needs to be treated may be missed if your intestines are not cleaned out.
Your health care provider will give you the steps for cleansing your bowel. This is called bowel preparation. Steps may include:
You need to drink plenty of clear liquids for 1 to 3 days before the test. Examples of clear liquids are:
You will likely be told to stop taking aspirin, ibuprofen, naproxen, or other blood-thinning medicines for several days before the test. Keep taking your other medicines unless your doctor tells you otherwise.
You will need to stop taking iron pills or liquids a few days before the test, unless your provider tells you it is OK to continue. Iron can make your stool dark black. This makes it harder for the doctor to view inside your bowel.
How the Test will Feel
The medicines will make you sleepy so that you may not feel any discomfort or have any memory of the test.
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.
After the exam, you may have mild abdominal cramping and pass a lot of gas. You may also feel bloated and sick to your stomach. These soon go away.
You should be able to go home 1 hour after the test. You must plan to have someone take you home after the test, because you will be woozy and unable to drive. The providers will not let you leave until someone arrives to help you.
When you are home, follow instructions on recovering from the procedure. These may include:
Why the Test is Performed
Colonoscopy may be done for the following reasons:
Normal findings are healthy intestinal tissues.
What Abnormal Results Mean
Abnormal test results may mean any of the following:
Risks of colonoscopy may include any of the following:
Chernecky CC, Berger BJ. Colonoscopy - diagnostic. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:358-359.
Itzkowitz SH, Potack J. Colonic polyps and polyposis syndromes. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology/Diagnosis/Management. 10th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 126.
Lieberman DA, Rex DK, Winawer SJ, et al. United States Multi-Society Task Force on Colorectal Cancer. Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer. Gastroenterology. 2012;143:844-857. PMID: 22763141 www.ncbi.nlm.nih.gov/pubmed/22763141.
National Comprehensive Cancer Network. NCCN clinical practice guidelines in oncology: colorectal cancer screening. Version 1.2015. www.nccn.org/professionals/physician_gls/pdf/colorectal_screening.pdf. Accessed February 11, 2016.
Review Date: 1/28/2016
Reviewed By: Subodh K. Lal, MD, gastroenterologist at Gastrointestinal Specialists of Georgia, Austell, GA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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