How is colon cancer diagnosed?

If a doctor thinks a patient may have gastrointestinal and colorectal cancer, the doctor will review the patient's medical history, family history, and symptoms, and will perform a physical examination including digital rectal exam). The doctor will order other tests if necessary, including the following:

  • Fecal occult blood test to check for blood in the stool
  • Blood tests, including blood chemistry and complete blood count, to determine the number of red blood cells, and check for anemia.
  • Examination of the colon by sigmoidoscopy or colonoscopy. For these tests, the bowel is cleaned with a solution, and an instrument (usually flexible) is inserted through the rectum to check the lining of the colon. A sigmoidoscopy is an examination of the lower colon; a colonoscopy examines the entire colon. The doctor can also use the instrument to take samples of polyps for biopsy (a small sample of tissue is removed and examined under a microscope for cancer).
  • Lower GI series. The patient is given a barium enema (barium is a substance that allows cancers or other abnormalities to stand out on x-ray), and then has a series of x-rays taken.

What are the stages of colorectal cancer?

One of the biggest concerns about a cancer diagnosis is whether the cancer has spread (metastasized) beyond its original location. To determine this, the doctor assigns a number (I through IV) to the diagnosis. The higher the number, the more the cancer has spread throughout the body. This is called "staging."The stages of colorectal cancer include the following:

  • Stage I: The cancer has penetrated into the middle layers of the colon wall but not through it.
  • Stage II: The colorectal cancer has penetrated through the muscle wall of the colon.
  • Stage III: The cancer has moved to lymph nodes near the colon and rectum.
  • Stage IV: The cancer has spread to lymph nodes and to other sites in the body, such as the liver, lungs or lining of the abdomen (peritoneum).

Reviewed by a Cleveland Clinic medical professional.

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