Colorectal cancer screening is a type of test that checks for cancer of your rectum and colon (large intestine) even though you may not have any symptoms. Several tests may be used to check for colorectal cancer.
Why is it important?
Colorectal cancer is the second leading cause of cancer deaths in the US, even though it is one of the cancers that can be prevented.
Colorectal cancer screening checks for polyps as well as cancer. Polyps are growths inside your bowel that sometimes turn into cancer. When polyps are found early, they can be removed to prevent cancer.
Colorectal cancer screening can also find cancer in its early stages, before it causes symptoms. If cancer is found early, it can often be cured by surgery. Unfortunately, without screening, colorectal cancer is often found too late for a cure.
What are the screening tests?
Several tests may be used to check for colorectal cancer and polyps.
FOBT (fecal occult blood test) or FIT (fecal immunochemical test) are lab tests that look for hidden blood in your bowel movements (stool), which may be a sign of cancer. Your provider will give you test kits that you will use at home. Follow the instructions that come with the kit for getting samples of bowel movements and for returning the cards to a lab. Read all of the instructions that come with the test kit before you start. With the FOBT test, you may need to avoid some medicines or foods for several days before you collect your stool sample. Follow any other instructions your healthcare provider gives you.
If either the FOBT or the FIT test finds blood, more tests need to be done to look for the cause. Some conditions other than cancer, such as an ulcer, can cause a positive stool blood test.
Flexible sigmoidoscopy use a thin, flexible, lighted tube that is put into your rectum and lower part of your colon to look for cancer and polyps. Your healthcare provider can use the scope to remove polyps or other tissue. The tissue will be checked for cancer in the lab. Your rectum and lower colon needs to be cleaned out before this test. Follow your healthcare provider’s instructions for diet, liquids, laxatives or enemas before the test. This test usually takes about 20 minutes and although it can be a bit uncomfortable, you usually don’t need medicine to help you relax during the test.
Colonoscopy uses a longer scope and can check your rectum and most or all of your colon. Your healthcare provider can use the scope to remove polyps or other tissue. The tissue will be checked for cancer in the lab. Your colon needs to be cleaned out before this test. Follow you healthcare provider’s instructions for diet, liquids, laxatives or enemas before the test. During the test, your healthcare provider will give you medicine to help you relax.
Virtual colonoscopy is a way to look at the colon without putting a scope into the rectum. Pictures of the colon are taken using X-rays and a computer (computerized tomography, or CT). This test is not yet widely available, and it has not been shown to be as accurate as actual colonoscopy. If abnormal tissue is seen with this test, then you will need a regular colonoscopy to remove it. You will need to take liquids only and use a laxative or enema to clean out your bowel before the test. This lets your healthcare provider see all of the tissue lining the colon.
Double-contrast barium enema uses barium, which is a chalky liquid that shows up on X-rays, to check your rectum and colon. A tube is inserted into your rectum. Fluid containing barium is passed through the tube into your rectum and colon. The flow of barium in the colon can be seen with a fluoroscope, which is a special X-ray machine. Barium sticks to the walls and highlights them to show any abnormal areas. Other names for this test are air contrast barium enema, lower gastrointestinal (GI) exam, and lower GI. You will need to take liquids only and use a laxative or enema to clean out your bowel before the test. This lets your healthcare provider see all of the tissue lining the colon.
When should I have screening tests for colorectal cancer?
If you are 50 to 75 years old and have an average risk of colon cancer, you should be screened with 1 of these 3 methods:
Have your stool checked for blood with a FOBT or FIT once a year.
Have a sigmoidoscopy exam every 5 years with FOBT or FIT at least every 3 years between the 5-year exams.
Have a colonoscopy every 10 years. If you have not recently had a colonoscopy and the results from other tests show blood or abnormal tissue, then you will need to have a colonoscopy to check for cancer.
Barium enema may be done every 5 years instead of colonoscopy or sigmoidoscopy. This test may be done instead of a colonoscopy if you have certain conditions, such as a colon that is very twisted. (The twists make it difficult to pass the scope through the colon.)
If you have a parent, brother, or sister who has had polyps or cancer in the colon, especially before they were 50 years old, you may have a higher risk for polyps or cancer. In this case, your healthcare provider may want to start screening you before you are 50. You may also need to be checked more often than the regular screening guidelines recommend.
Ask your provider when and how often you should be tested for colorectal cancer.
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Adult Advisor 2015.1 published by RelayHealth. Last modified: 2014-03-10 Last reviewed: 2014-03-10
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
National Cancer Bulletin. Experts Recommend Steps to Increase Colorectal Cancer Screening in Primary Care. US Dept of Health and Human Services, National Cancer Institute, National Cancer Bulletin, Feb. 9, 2010, v.7, no.3. Accessed April 19, 2010 from http://www.cancer.gov/ncicancerbulletin/020910/page5.