How is Colon Cancer Diagnosed?
Any or all of the tests listed below could be done to find a colon cancer. Some tests may be paired together, such as the digital rectal exam and the sigmoidoscopy.
- Digital Rectal Exam (DRE)
A doctor inserts a gloved and lubricated finger into the rectum to feel for lumps or other abnormal areas. It is used as the first method of detection for rectal cancer.
- Fecal Occult Blood Test (FOBT)
- A test to see if there is hidden blood in the stool. A positive result may be a sign of cancer or polyps.
- Barium enema
- X-ray of the entire lower bowel using barium solution which is given through the rectum. This test can find polyps, cancer, colitis, and diverticulosis. Laxatives and regular enemas are used before the test to clean the bowel.
- Sigmoidoscopy
- An examination of the rectum and lower (sigmoid) colon with a hollow lighted tube. It is used to find colon polyps, cancer and/or to find the cause of bleeding. Tissue can be removed for a doctor to look at under a microscope to make a diagnosis. Laxatives must be used before the test to clean the bowel.
- Colonoscopy
- A test that looks in the rectum and entire colon by using a tube that is lighted and flexible. It may reveal polyps, cancer, colitis and diverticulosis. Tissue can be removed for a doctor to look at under a microscope to make a diagnosis. May require sedation. Laxatives must be used before the test to clean the bowel.
- Virtual colonoscopy (also called CT colonoscopy)
- A CT (computerized tomography) scan creates cross section images of the body, which may show cancer or its spread to other organs. Laxatives must be used before the test to clean the bowel.
- Complete blood count (CBC)
- A sample of blood is drawn and looked at for the number of red and white blood cells, platelets, hemoglobin (protein that carries oxygen), and the percentage of the blood sample that is red blood cells.
- Carcinoembryonic antigen assay (CEA)
- CEA is a tumor marker in the blood that may be a sign of certain types of cancer cells. It is often high in some people with colon cancer.
- Liver Function Tests (LFT)
- A group of blood tests that measures enzymes and proteins that give an indication of the health of the liver.
- DNA Stool test
- A stool sample is examined for abnormal DNA that may be a sign of colorectal cancer. This technology is still undergoing testing to see if it is more effective at finding cancer cells earlier than other screening options.
Source: UI Cancer Information Service
Last Reviewed: March 2011