Screening for Colorectal Cancer

The purpose of screening is early diagnosis and treatment. Screening tests are usually administered to people without current symptoms, but who may be at high risk for certain diseases or conditions.

Screening Tests

Digital Rectal Exam—Your healthcare provider will examine the rectum for lumps or abnormal areas by inserting a lubricated, gloved finger into the rectum. About half of colorectal cancers can be diagnosed in this way, so it is important not to skip this part of your physical exam.

Fecal Occult Blood Test—A small sample of stool is placed on a special card and tested by a lab for hidden blood, which often comes from a bleeding cancer. Any positive test for occult blood should be followed up as suspicious (though not completely diagnostic) for cancer.

Sigmoidoscopy—The doctor inserts a sigmoidoscope (thin, lighted tube with a tiny camera attached) into the rectum to view the inside of the lower colon and rectum for polyps, tumors, or abnormal growths.

Colonoscopy—A colonoscopy examines the inside of the entire colon and rectum using a thin, lighted tube with a tiny camera attached, which is inserted into the rectum. If a polyp or abnormal tissue is discovered during this exam, it may be removed and reviewed for further testing.

A colonoscopy can be done by inserting a tube into the rectum (endoscopic colonoscopy), by swallowing a special camera device (capsule endoscopy, which is only available at certain centers), or by the use of highly specialized body scans ( virtual colonoscopy ). Your physician will discuss the techniques available in your area and help you decide which is the best option. Most patients undergo traditional endoscopic colonoscopy.

Barium Enema—A barium liquid is put into the rectum by way of the anus. Barium is a metallic compound that helps highlight the image of the lower gastrointestinal tract on an x-ray.

Virtual Colonscopy—A more comfortable procedure, virtual colonoscopy is a type of CT scan that uses computer software along with CT imaging to examine to colon for polyps. A rubber catheter is used to introduce air into the colon, but this procedure does not require the introduction of firm tubes (as do endoscopy and barium enema). Therefore, there is not the risk of possible injury to the bowel. You are not sedated, so recovery time is shorter. Additionally, you do not need to arrange for transportation to and from the procedure as with endoscopy.

Studies indicate that virtual colonscopy is almost as effective as endoscopy for determining the presence of polyps. However, if a polyp is found by virtual colonoscopy, a second procedure is necessary to remove and examine it—making this test inappropriate if you have a higher risk for developing polyps. With conventional endoscopy, the biopsy can usually be done at the same time. Virtual colonscopy is not available everywhere.

Screening Guidelines

The decision to screen will likely be made on an individual basis based on your risk factors. The American College of Gastroenterology suggests the following guidelines:

For people at average risk

Beginning at age 50:

  • Annual fecal occult blood test (FOBT)
  • Flexible sigmoidoscopy every 5 years
  • Annual FOBT plus flexible sigmoidoscopy every 5 years
  • Barium enema every 5 to 10 years
  • Colonoscopy every 10 years

For people with a first degree relative with onset of colorectal cancer after age 60

  • Begin screening at age 40
  • Preferred screening: Colonoscopy every 10 years or more frequently, depending on the colonoscopy findings

For people with a first degree relative with onset of colorectal cancer before age 60

  • Begin screening at age 40 or 10 years younger than age of diagnosis of the affected relative (whichever is first)
  • Preferred screening: Colonoscopy every 3 to 5 years


American College of Gastroenterology website. Available at: .

Last reviewed April 2007 by Barbara Harty-Golder, MD, JD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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