What are screening tests for colorectal cancer?
Screening tests can find polyps or cancers before they are large enough to cause any symptoms. Screening tests are important because early detection means that the cancer can be more effectively treated. Your doctor will choose the tests that are right for you. The following are some screening tests for colorectal cancer:
Digital Rectal Exam
. In this exam, your doctor puts his or her gloved finger into your rectum to find any growths. This exam is simple to do and is not painful. However, because this exam can find less than 10% of colorectal cancers, it must be used along with another screening test.
. For this test, you are given an enema (injection of fluid into the rectum) with a liquid that makes your colon show up on an X-ray. Your doctor looks at the X-ray to find abnormal spots in your entire colon. If you have an abnormal spot or if the radiologist detects polyps in your colon, your doctor will probably want you to have colonoscopy.
Fecal Occult Blood Test
. This test checks your stool for blood that you can't see. Your doctor gives you a test kit and instructions to use it at home. Then you return a stool sample to your doctor for testing. If blood is found, another test is done to look for a polyp, cancer or another cause of bleeding. Your doctor will also ask you to not eat certain foods or take certain medicines that may interfere with test results a few days before the test.
Certain foods and medicines can make this test turn out positive, even though you don't really have blood in your stool. This is called a "false-positive" test. These include some raw vegetables, horseradish, red meat, non-steroidal anti-inflammatory drugs (such as ibuprofen), blood thinners, vitamin C supplements, iron supplements and aspirin. Some medical conditions, like hemorrhoids, can also cause a false-positive test result.
Stool DNA Test
. This test checks your stool for cells that are shed by colon cancers or precancerous polyps. Your doctor will give you a test kit with instructions on how to collect a stool sample. Your doctor may also ask you to not eat certain foods or take certain medicines that may interfere with test results a few days before the test. If your test turns out positive, your doctor will probably want you to have a screening test called colonscopy.
. Colonoscopy is well tolerated and rarely causes much discomfort. There is often a feeling of pressure, bloating, or cramping at times during the procedure. Your doctor may give you medication through a vein to help you relax and better tolerate any discomfort from the procedure. You will be lying on your side or back while the colonoscope is advanced slowly through the large intestine (colon). The colonoscope is then slowly withdrawn and the lining of the intestine is examined. The procedure usually takes 45-60 minutes.
. In this test, your doctor puts a thin, flexible, hollow tube with a light on the end into your rectum. The tube is connected to a tiny video camera so the doctor can look at the rectum and the lower part of your colon.
This test can be a bit uncomfortable, but it lets your doctor see polyps when they are very small (before they can be found with a fecal occult blood test). Because flexible sigmoidoscopy may miss cancerous polyps that are in the upper part of the colon, some doctors prefer a colonoscopy. Your doctor will discuss these options with you.
For more information, please visit the American Society Gastrointestinal Endoscope’s website: Understanding Colon Cancer Screening