How do doctors screen for colorectal cancer?

Dr. David A. Berg, MD
Colorectal Surgeon

Doctors screen for colorectal cancer by performing a colonoscopy, a test designed to catch colorectal cancer early, when it is more easily treated. Experts recommend men and women get their first colonoscopy at age 50. Blacks should begin screenings at age 45. If the doctor finds a polyp, he or she will likely remove it and have it sent for testing to see if it is cancerous. That's what makes colonoscopy unique. One test can both screen for and prevent the same cancer.

If tests reveal no polyps,conoscopy may be repeated in 10 years. If polyps are found, tests would typically be repeated in three to five years.

Besides colonoscopy, there are other screening tests for colorectal cancer.

Sigmoidoscopy is similar to colonoscopy but only looks at the lower part of the colon and rectum. Others include barium enema and computed tomography (CT) colonography, also known as virtual colonoscopy. A fecal occult blood test, fecal immunochemical test and stool DNA test examine a stool sample for signs of cancer, but are less likely to detect polyps. If the results of any of these tests are abnormal, a full colonoscopy should be performed.

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Juliet Wilkinson
Oncology Nursing Specialist

There are a variety of screening tests for colorectal cancer, ranging from the quick and easy (but not definitive) to the invasive.

  • Stool blood tests, such as a fecal occult blood test, can pick up microscopic bleeds within the colon.
  • Diagnostic imaging studies, such as a barium enema or a computed tomography (CT) scan, can show structural irregularities, such as a mass, within the colon.
  • Digital rectal exams can alert your doctor to large masses within the rectum.
  • Colonoscopy or sigmoidoscopy is used to visualize the inside of the colon and detect abnormal tissues.

If you have concerns, schedule an appointment with your doctor so you can stop anticipating the worst and start dealing with the actual.

To find polyps or early cancer, healthcare providers may suggest one or more tests for colorectal cancer screening:

  • Flexible sigmoidoscopy every five years. Doctors use a flexible, lighted tube (sigmoidoscope) to look at the interior walls of the rectum and part of the colon.
  • Colonoscopy every 10 years. Doctors use a flexible, lighted tube (colonoscope) to look at the interior walls of the rectum and the entire colon. During this procedure, samples of tissue may be collected for closer examination or polyps may be removed.
  • Double-contrast barium enema every five years. Adults are given an enema with a barium solution, and air is pumped into the rectum. Several x-ray pictures are taken of the colon and rectum, where polyps or tumors may present.
  • Computed tomography (CT) colonography (virtual colonoscopy) every five years. This method is under investigation. Advanced CT scan of the colon and rectum produces two- and three-dimensional images of the colon and rectum that allow a doctor to look for polyps or cancer.
  • Fecal occult blood test (FOBT) every year, checking for hidden blood in three consecutive stool samples.
  • Digital rectal exam, often part of a routine physical examination.

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