Beginning at age 50, both men and women at average risk should follow one of the following five screening options:

1. Yearly stool blood test (fecal occult blood test–FOBT) or fecal immunochemical test (FIT) – FOBT is used to find small amounts of hidden (occult) blood in the stool. A sample of stool is tested for traces of blood. People having this test will receive a kit with instructions that explain how to take stool samples at home. The kit is then sent to a lab for testing. If the test is positive, further tests will be done to pinpoint the exact cause of the bleeding.

FIT is a newer kind of stool blood test. It is very much like the FOBT but is perhaps a little easier to do and it gives a fewer number of false positive results.

For the stool blood test, the take-home, multiple-sample method should be used.

2. Flexible sigmoidoscopy every 5 years – A sigmoidoscope is a slender, lighted tube about the thickness of a finger. It is placed into the lower part of the colon through the rectum. This allows the doctor to look at the inside of the rectum and part of the colon for cancer or polyps. Because the tube is only about 2 feet long, the doctor is only able to see about half of the colon. The test can be uncomfortable, but it should not be painful. Before the test, you will need to take an enema to clean out the lower colon.

3. Yearly stool blood test plus flexible sigmoidoscopy every 5 years -- Of these first three options, the American Cancer Society prefers this one – that is, FOBT or FIT every year plus flexible sigmoidoscopy every five years.

4. Double contrast barium enema every 5 years – A chalky substance is used to partly fill and open up the colon. Air is then pumped in to cause the colon to expand. This allows good x-ray films to be taken. You will need to use laxatives the night before the exam and have an enema the morning of the exam.

If anything abnormal is found on any of the above tests, a colonoscopy should be done.

5. Colonoscopy every 10 years– The doctor examines the patient’s rectum and entire colon with a thin, lighted tube. If polyps or other abnormal tissue are found, they can be removed immediately during the exam.

While a digital rectal exam (DRE), in which the doctor examines the patient’s rectum with a gloved finger, is often done as part of a regular physical exam, it should not be used as a stand-alone test for colorectal cancer.

People with certain risk factors should begin screening earlier or have screening more often. Talk to your doctor about your own risk and when you should have screening tests.

Other Tests
To help confirm the diagnosis and determine the stage of the cancer, a doctor may use a variety of other tests, which, along with colonoscopy, include:

• CT (Computed Tomography) Scan– Uses x-rays to take many pictures of the body that are then combined by a computer to give a detailed picture. A CT scan can often show whether the cancer has spread to the liver, lungs, or other organs. CT scans can also be used to help guide a biopsy needle into a tumor. CT scans take longer than regular x-rays. The patient has to lie still on a table while the CT scan is being done. A contrast "dye" may be injected or a special drink used to help outline the area being viewed.

A new way to use a CT scan is to do a "virtual colonoscopy." After stool is cleaned from the colon and the colon is filled with air, a computer can put together a picture of the inside of the colon. This method requires the same preparation as for a colonoscopy and there is some discomfort from the bowel being filled with air. If anything not normal is seen, a follow-up colonoscopy will be needed. Note: Virtual colonoscopy is still being studied and is currently not included among the tests recommended by the American Cancer Society or other major medical organizations as a screening test for colorectal cancer polyps or for the early detection of colorectal cancer.

• MRI (Magnetic Resonance Imaging)– A special imaging technique used to image internal structures of the body, particularly the soft tissues. An MRI image is often superior to a normal X-ray image. These scans may be used for detecting some cancers or for following their progress.

•PT ( Positron Emission Tomography) Scan– A scanning device that uses low- dose radioactive sugar primarily to measure brain activity, it is also a limited-use diagnostic tool for colorectal cancer that can be particularly helpful in finding out the extent to which the disease may have spread. In cancer, cells begin to grow at a much faster rate, feeding on sugars. The radioactive substance, called a tracer, travels through the body, emitting signals along the way and eventually collecting in the colorectal area. If the organ is cancerous, the tracer’s signals will be stronger since more sugar will be absorbed. If the lymph nodes near the tumor or if a distant organ is cancerous, they will also absorb more of the radioactive sugar and emit a stronger signal.