Diagnosis

If your signs and symptoms indicate that you could have colon cancer, your doctor may recommend one of more tests and procedures, including:

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• Blood tests. Blood tests do not diagnose cancer, but can be used to indicate whether there is a problem present. The doctor will use the results to determine if further tests are needed. 
• Using dye and X-rays to make a picture of your colon. A barium enema allows your doctor to visualize your entire colon with an X-ray. Barium, a contrast dye, is placed into your bowel in an enema form. During a double-contrast barium enema, air also is added. The barium fills and coats the lining of the bowel, creating a clear silhouette of your rectum, colon and sometimes a small portion of your small intestine.
• Using a scope to examine the inside of your colon. Colonoscopy uses a long, flexible and slender tube attached to a video camera and monitor to view your entire colon and rectum. If any suspicious areas are found, your doctor can pass surgical tools through the tube to take tissue samples (biopsies) for analysis.
• Using multiple CT images to create a picture of your colon. Virtual colonoscopy combines multiple computerized tomography (CT) images to create a detailed picture of the inside of your colon. If you're unable to undergo colonoscopy, your doctor may recommend virtual colonoscopy.