Just talking about a colonoscopy makes most people cringe. That's probably because the idea of having a tube inserted into your rectum and colon is disturbing.

But even more disturbing for many people is the thought of getting colorectal cancer. But when diagnosed at an early stage, before the cancer has invaded the colon wall or spread to distant sites, the chances of survival are high.

Still, by definition, all screening tests are performed on people who feel fine except for the anxiety they have about their future health.

What about colorectal screening? Is the unpleasant prospect of having a colonoscopy or some other equally disagreeable procedure really worth it? For many of us, the answer is “yes”.

Screening Tests: What Do They Entail?

Colorectal screening tests are designed to detect cancer or fingerlike projections of tissue called polyps. Polyps may be cancerous or precancerous. Although most polyps are not cancerous, the vast majority of colorectal cancers are believed to begin as polyps.

Here's what's involved with each screening test to detect polyps and colorectal cancer:

Fecal Occult Blood Test

The fecal occult blood test is a test for hidden blood in a sample of stool (feces) you have already passed. Blood in your feces may be the result of bleeding from a cancerous polyp in your colon or rectum, or it may be a sign of a more benign condition.

Stool DNA Test

This is a non-invasive method of testing a specimen of stool (feces) for altered DNA which is shed by colon cancer or polyps into the stool. It is more expensive than fecal occult blood testing. The sensitivity for detecting cancer with this test is variable. One limitation is that this test does not detect all types of colon cancer.

Flexible Sigmoidoscopy

For a flexible sigmoidoscopy, a thin, lighted tube is inserted into the rectum and lower colon to examine their internal mucosal lining. Images can be recorded while the doctor looks for polyps and other abnormalities on a monitor. This procedure does not look at the entire length of the colon like a colonoscopy does.

Colonoscopy

For a colonoscopy, a thin, lighted tube similar to a flexible sigmoidoscope is used. This time, the lighted tube goes all the way through to the end of your colon where it connects to the small intestine. Polyps that are detected can be removed during the procedure.

Double-Contrast Barium Enema

A double-contrast barium enema involves the injection of a fluid called barium followed by air into your rectum. This makes your entire colon visible on an x-ray, allowing doctors to see abnormal growths, like polyps.

Computed Tomography (CT) Colography

Computed tomography colography (“virtual colonoscopy”) is a technique that takes computer generated x-ray images after injection of air into the colon. One disadvantage to having this test compared to a colonoscopy is if a polyp is discovered during colonoscopy it can be removed right then and there, while if one is detected with virtual colonoscopy, a follow up real colonoscopy will be necessary.

Screening Recommendations

The American Cancer Society suggests that starting at age 50, men and women should be screened for colorectal cancer with one of the following options:

  • flexible sigmoidoscopy every 5 years; or
  • double-contrast barium enema every 5 years; or
  • CT colonography (virtual colonoscopy) every 5 years; or
  • colonoscopy every 10 years; or
  • yearly fecal occult blood test (preferably the take-home, multiple sample method); or
  • yearly fecal immunochemical test every year; or
  • stool DNA test, interval uncertain.

However, people at increased risk of colorectal cancer may need to have some of these tests earlier in life and more often. Some reasons why you would be considered high risk are:

  • Personal or family history of colorectal cancer or adenomatous polyps
  • Personal history of chronic inflammatory bowel disease, such as ulcerative colitis or Crohn's disease

What Tests Do You Need?

Talk to your doctor about the advantages and disadvantages of each screening test, especially if your risk for colorectal cancer is greater than average. These tests may save your life.