Colon and Rectal Cancer Screening

What is colon and rectal cancer screening?

The colon, also known as the large bowel, is a common area for patients to develop cancer. Since it is relatively easy to examine this area of the digestive system, it is also possible to find and prevent these cancers before it grows or spreads. Colon and rectal cancer (colorectal cancer) starts as small growths (polyps) which grow over time. The aim is to evaluate the colon and rectum for these polyps and remove them before they become cancer. Colon and rectal cancer screening is a way in which doctors check the colon and rectum for signs of cancer or growths (polyps) that might become cancer. It is done in people who have no symptoms and no reason to think they have cancer.

Studies show that having colon cancer screening lowers the chance of dying from colon cancer. There are 5 or 6 screening tests that can do this.

What are the different screening tests for colon cancer?


A colonoscopy allows visualization of the inside the entire colon. Advantages of this test is that this way we can find most small polyps and almost all large polyps and cancers. If found, polyps can be removed right away. The drawback to this test is that it has more risks than the other screening tests. In 1 in 1000 people, it can cause bleeding or tear the inside of the colon. Cleaning out the bowel beforehand can be unpleasant.


This investigation is very similar to a colonoscopy. The difference is that this test looks only at the last part of the colon, and a colonoscopy looks at the whole colon. Therefore this is a good investigation only to rule out cancer in the last part of the colon.

CT colonography

also known as virtual colonoscopy or CTC) Here a special type of CT scan is performed, and can be done without any sedation. Unfortunately polyps cannot be removed and no biopsies can be taken.

Barium enema

This is an older kind of X-ray test. To prepare for a barium enema, you must clean out your colon. On the day of the test, a doctor or nurse squirts a fluid that shows up on X-rays into your rectum and then takes X-rays to create pictures of the colon. This test is not used much anymore. Polyps or cancers cannot be removed during a barium enema, and CT colonography is better at finding problems.

Stool test for blood

Stool tests most commonly check for blood in samples of stool. Cancers and polyps can bleed, so blood will show up in the stool. Other less serious conditions can also cause small amounts of blood in the stool, and that will show up in this test.

Stool test for DNA

This is a newer test that that checks for colon cancer genes in a stool sample. The test is expensive, and some experts feel it has not been studied enough to use in screening.

Who should be screened for colon cancer?

Doctors recommend that most people begin having colon cancer screening at age 50. People who have an increased risk of getting colon cancer sometimes begin screening at a younger age. That might include people with a strong family history of colon cancer, and people with diseases of the colon called "Crohn's disease" and "ulcerative colitis." Most people can stop being screened around the age of 75, or at the latest 85.

How often should I be screened?

That depends on your risk of colon cancer and which test you have. Discuss this with your doctor. Most people can choose 1 of these schedules: