Colorectal Cancer

How is colorectal cancer diagnosed?

There are a number of different tests that can be used to detect polyps, cancer or other abnormalities in the colon and rectum.

Before some of these tests, the colon must be completely empty and the doctor may prescribe an enema or a liquid laxative. This preparation is very important in ensuring the test accuracy.

Diagnostic tests include:

• Colonoscopy
• Part of regular screening and diagnostic procedures, a colonoscopy examines the colon and rectum using a special flexible camera inserted through the anus. It allows the removal of small polyps and taking of tissue samples (biopsies) of any abnormal areas.
• Digital rectal examination
  Often part of a routine physical examination, the doctor checks the lower most area of the rectum by inserting a lubricated gloved finger into the rectum and gently feeling for abnormal growths. The exam may be uncomfortable but should not be painful.
• Double Contrast Barium Enema
  • In this procedure, the colon and rectum is filled with a white liquid, called barium, that helps x-rays show extra details, including polyps, in the large intestines better than normal x-rays.
• Computed Tomographic Colonography (CTC)
  • A CTC or virtual colonoscopy creates a 3D image of the colon to reveal any abnormal masses. Images are taken seconds after the colon is inflated with carbon dioxide through a small rectal tube and is sensitive enough to detect more abnormal growths than other tests.
• Flexible sigmoidoscopy
  • A narrow lighted tubular instrument called a sigmoidoscope is passed into the rectum allowing the doctor to look into the rectum and left-sided part of the colon. This also enables taking of tissue samples (biopsies) of any abnormal areas.

If diagnosed with colon cancer, the doctor may recommend further tests to determine the extent or stage of cancer. These are usually imaging tests for the abdominal, pelvic and chest areas.

In some cases, the extent of the cancer will only be known after surgery.