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 doctor will insert a lubricated gloved finger into the rectum. The doctor will check the rectum for lumps or abnormal areas. About half of colon cancers can be detected in this way, especially if a test for occult blood is done at the same time. It is not a good idea to ask your doctor to skip your rectal exam during a routine checkup. It is a good idea to agree to having your stool tested for occult blood.

]]>Fecal Occult Blood Test]]>—A small sample of stool is placed on a special card. It is then tested by a lab for hidden blood. Blood can be present in the stool for many reasons. Colorectal cancer will not always cause blood in the stool. If positive, the test should be followed up with a more specific test such as endoscopy. A negative result does not guarantee that colorectal cancer is not present.

]]>Sigmoidoscopy]]>—A sigmoidoscope is a thin, lighted tube with a tiny camera attached. It is inserted into the rectum to view the inside of the lower colon and rectum. The doctor will use it to search for polyps, tumors, or abnormal growths.

]]>Colonoscopy]]> —A thin, lighted tube with a tiny camera attached is inserted into the rectum. The inside of the entire colon and rectum are examined. If a polyp or abnormal tissue is discovered, it may be removed and reviewed for further testing. For most patients, this is the standard for examining the colon.

A colonoscopy can be done by inserting a tube into the rectum (endoscopic colonoscopy) or by the use of highly specialized body scans ( virtual colonoscopy). Your doctor 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 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. This procedure is still being studied. Some of the benefits of a virtual colonoscopy include:

  • Does not require the introduction of firm tubes (as do endoscopy and barium enema)
  • No risk of possible injury to the bowel
  • Sedation is not needed, recovery time is shorter
  • Transportation to and from the procedure is not needed

Some 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. Virtual colonoscopy is not appropriate 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