Colon cancer screening

Colon cancer is one of the leading causes of cancer-related deaths in the United States. The good news is that early diagnosis through preventive screening often leads to a complete cure.

Colorectal cancer starts in the large intestine, also known as the colon. Nearly all colon cancers begin as noncancerous, or benign, polyps, which slowly develop into cancer. Screening can detect these polyps and early cancers. The great thing is that we can remove polyps years before cancer even has a chance to develop!

Your doctor can use several tools to screen for cancer. The first step is a stool test. This test checks your bowel movements for blood that you may not even be able to see in your stool. Polyps in the colon and small cancers can bleed tiny amounts of blood that you can't see with the naked eye. The most common method is called the fecal occult blood test.

A second method is called a sigmoidoscopy exam. This test uses a flexible scope to look at the lower portion of your colon. But, because it looks only at the last one-third of the large intestine, it may miss some cancers. That's why this test is usually done along with a stool test.

A colonoscopy is similar to sigmoidoscopy, but it can see the entire colon. That's why we usually do colonoscopies over sigmoidoscopies nowadays. You'll usually be mildly sedated during this test.

Occasionally, your doctor may recommend, as an alternative, a double-contrast barium enema--which is a special x-ray of the large intestine, or a virtual colonoscopy, which uses a CAT scan and computer software to create a 3-D image of your large intestine.

So, who should be screened for colon cancer? Well, beginning at age 50, men and women should have a screening test. People with an average risk of colon cancer should have a colonoscopy every 10 years, a double-contrast barium enema every 5 years, or a fecal occult blood test every year. Additional options are sigmoidoscopy every 5 to 10 years.

People with certain risk factors for colon cancer may need screening before age 50, or more frequent testing. Such people include those with a family history of colon cancer, African-Americans, those with a history of previous colon cancer or polyps, or folks with a history of ulcerative colitis or Crohn's disease, which are both chronic inflammatory bowel diseases.

The death rate for colon cancer has dropped in the past 15 years and this may be due to increased awareness and colon screening. In general, early diagnosis can lead to a complete cure.

Version Info

  • Last reviewed on 11/16/2011
  • Mitchell W. Hecht, MD FACP, Internal Medicine private practice in Roswell, GA; author of the nationally-syndicated medical column 'Ask Dr. H.' Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

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