The purpose of screening is early diagnosis and treatment. Screening tests are usually administered to people without current symptoms, but who may be at high risk for certain diseases or conditions.
Fecal Occult Blood Test—A small sample of stool is placed on a special card. It is then tested by a lab for hidden blood.
Blood can be present in the stool for many reasons. Colorectal cancer will not always cause blood in the stool. If positive, the test should be followed up with a more specific test such as endoscopy. A negative result does not guarantee that colorectal cancer is not present.
Usually multiple samples are collected.
Sigmoidoscopy—A sigmoidoscope is a thin, lighted tube with a tiny camera attached. It is inserted into the rectum to view the inside of the lower colon and rectum. The doctor will use it to search for polyps, tumors, or abnormal growths.
Colonoscopy—A thin, lighted tube with a tiny camera attached is inserted into the rectum. The inside of the entire colon and rectum are examined. If a polyp or abnormal tissue is discovered, it may be removed and reviewed for further testing.
For most patients, this is the standard for examining the colon.
Barium Enema—A barium liquid is put into the rectum by way of the anus. Barium is a metallic compound that helps highlight the image of the lower gastrointestinal tract on an x-ray.
Computed tomographic colonography—A type of CT scan that uses computer software along with CT imaging to examine to colon for polyps. A rubber catheter is used to introduce air into the colon.
Fecal Immunochemical Test—Like a fecal occult blood test, a sample of stool is placed on a special card. It is tested for hidden blood that reacts to a protein found in red blood cells. Blood from the upper part of the gastrointestinal tract, like the stomach, is not as likely to be detected. Unlike the fecal occult blood test, there is no dietary preparation required before taking the test.
Stool DNA Test—DNA cells are analyzed in a stool sample instead of blood. Colorectal cancer or polyp cells can be found in the stool. DNA tests look for genetic changes in the cells.
The decision to screen will likely be made on an individual basis based on your risk factors. Most guidelines suggest the following:
Beginning at age 50 (age may be younger for African-Americans and Native Americans), use one of the following methods:
- Annual fecal occult blood test (FOBT)
- Annual fecal immunochemical test (FIT)
- Stool DNA test every 3 years
- Flexible sigmoidoscopy every 5 years
- Double-contrast barium enema every 5 years
- Computed tomographic colonography every 5 years
- Colonoscopy every 10 years
- Begin screening at age 40
- Preferred screening: Colonoscopy every 10 years or more frequently, depending on the colonoscopy findings
- Begin screening at age 40 or 10 years younger than age of diagnosis of the affected relative (whichever is first)
- Preferred screening: Colonoscopy every 5 years
Colorectal cancer. American Cancer Society website. Available at: http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf. Updated January 17, 2013. Accessed May 14, 2013.
Colorectal cancer screening. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what. Updated May 6, 2013. Accessed May 14, 2013.
Rex DK, Johnson DA, Anderson JC, et al. American College of Gastroenterology guidelines for colorectal cancer screening 2009. Am J Gastroenterol. 2009;104(3):739-750.
Screening and testing to detect colon and rectal cancer. National Cancer Institute website. Available at: http://cancer.gov/cancertopics/screening/colon-and-rectal. Accessed May 14, 2013.
Last reviewed May 2013 by Mohei Abouzied, MD; Brian Randall, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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