Screening Tests

 

 

 

 

What are screening tests for colorectal cancer?

 

Screening tests are, by definition, evaluation intended to detect a condition at an earlier stage when an individual is asymptomatic.  Screening tests for colorectal cancer 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.  

 


 

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. Although this exam is simple to perform , because it can find less than 5% of colorectal cancers, it must be used along with another screening test.

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 on how to collect a stool sample. Then you return this sample or card to your doctor for testing. If blood is found, another test, usually a colonoscopy, 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 further testing to investigate the significance of this finding, usually a colonscopy.

This test is a laboratory-developed test, and is not subject to regulation by the U.S. Food and Drug Administration (FDA) and has not obtained FDA clearance or approval.

Colonoscopy

This is the most accurate method of colorectal detection.  This test allows a doctor to look at your entire colon by passing a thin, flexible tube with a light and camera on the tip through your rectum. The tube can also be used to remove polyps and sample suspected cancers during the exam. Colonoscopy may be briefly uncomfortable, but it is usually not painful as you are given medicines to relieve pain and make you relaxed and sleepy.  This does involve preparation of the bowel with a prescribed laxative regimen.

CT Colonography

This is a new test that uses a computerized tomography (CT) machine to take pictures of your colon. The radiologist can then see all of the images combined in a computer to check for polyps or cancer. If polyps or other abnormalities are detected in your colon, you will need to have a traditional colonscopy to examine them in more detail or to remove them. This does involve preparation of the bowel with a prescribed laxative regimen. Currently, this test is not covered by any medical insurance.

This test does not pick up small or flat polyps and test is generally not covered by most medical insurances.

Flexible Sigmoidoscopy

In this test, your doctor puts a thin, flexible tube with a light and camera on the end into your rectum and lower colon. This test can be a bit uncomfortable and may miss cancerous polyps that are in the upper part or the unexamined colon.This does involve preparation of the bowel with enema(s). 

Barium Enema

For this test, you are given an enema (injection of fluid into the rectum) with a contrast agent that makes your colon show up on an X-ray. A radiologist looks at the X-ray to find abnormal spots in your colon.  If the radiologist detects any abnormal spots in your colon, your doctor will probably want you to have colonoscopy to determine if these could be polyps or cancer.