How does my doctor know I have colorectal cancer?

If you have symptoms of colorectal cancer, your doctor will want to know why. To find out, your doctor is likely to ask you questions about the following things.

  • Your medical history
  • Your family history of cancer
  • Your lifestyle habits, including your diet, whether you smoke, and how active you are.

Your doctor may also ask for tests to check for colorectal cancer. Some of these tests are the same ones that are used for screening people who have no symptoms. The doctor could ask for any of these tests.

  • Digital rectal exam - This is an exam of your rectum. Your doctor inserts a lubricated, gloved finger into your rectum to feel for lumps or abnormal areas.
  • Fecal occult blood test, also called FOBT - This is a test to check your stool for blood that can only be seen with a microscope. You place small samples of stool on special cards and return them to your doctor or lab for testing.
  • Barium enema - This is a series of X-rays of your lower gastrointestinal tract. Before the X-rays, you'll get an enema into your rectum with a liquid that contains a silver-white metallic compound called barium. The barium coats your lower gastrointestinal tract so that it shows up better on X-rays. This procedure is also called a lowe GI series.
  • Sigmoidoscopy - A sigmoidoscopy lets your doctor see inside your anus, rectum, and lower colon, also called sigmoid colon. Because this test allows your doctor to look for hemorrhoids and other, noncancerous bowel disease, it's often done if you have unexplainable bleeding or pain in your rectum. It may also bedone if you have a change in bowel habits. The doctor inserts a sigmoidoscope, which is a thin, lighted tube, through your rectum into your sigmoid colon. It also lets the doctor biopsy the suspicious area.
  • Colonoscopy - A colonoscopy lets your doctor see inside your rectum and your entire colon. The doctor will use a thin, flexible, lighted tube called a colonoscope to perfrom this test.
  • Virtual colonoscopy - This investigational procedure uses a series of pictures made by a process called computed tomography, also called CT, to create a detailed image that may show polyps and anything else that seems unusual on the inside surface of your colon. This test is also called colonography or CT colonography. This does not allow the doctor to take a biopsy. You still may need a colonoscopy anyhow.
  • The results of these exams may be enough to rule out colorectal cancer. If not, your doctor may send polyps or tissue that was removed during an exam to the lab to be examined under a microscope. The exam can show whether there is abnormal cell growth, called dysplasia, or cancer. The process of removing tissue to be examined in a lab is called a biopsy. A biopsy can be done only via a sigmoidoscopy or a colonoscopy.

Reviewed By: Marc K. Wallack , MD
Chairman, Department of Surgery, St. Vincent's Hospital Manhattan, New York, NY
Reviewed By: Deborah Berg, RN, BSN
Oncology Nurse Consultant