Your doctor will ask about your symptoms, and medical and family history. The abdominal and rectal areas will be carefully examined. Your doctor may recommend different tests in order to identify abnormal growths and confirm diagnosis.
Suspicion of Colorectal Cancer
Bowel changes can be caused by many different factors. The following tests can be done in the office to start to look for signs of cancer or other possible problems. Tests may include:
- Digital rectal exam —Your doctor will insert a lubricated, gloved finger into the rectum. The rectum will be check for lumps or abnormal areas.
- Fecal occult blood test —A small sample of stool is placed on a special card. A lab will test for hidden blood. Blood can be caused by different health issues. If positive, other tests will be needed to confirm a cause. Colorectal cancer may also not cause bleeding. A negative result does not guarantee that colorectal cancer is not present.
- Blood tests —Certain substances are released into the blood when a tumor develops. These tumor markers may increase when cancer is present. Blood tests also evaluate blood cell counts. Low red blood cell counts may be present if there is bleeding in the intestine from cancerous growths.
Imaging and Visual Tests
Imaging and/or visual tests may be used to look for tumors. The tests can also show the size and location of tumors. Some tests use contrast material to highlight structures so images are more clear and detailed. Imaging tests may include:
- Sigmoidoscopy —A sigmoidoscope is a thin, lighted tube with a tiny camera attached. It is inserted into the rectum to view the inside of the lower colon and rectum. The doctor will use it to search for polyps, tumors, or abnormal growths. Polyps and abnormal tissue will be removed and examined under a microscope. Removal of a polyp is called a polypectomy.
- Colonoscopy —A thin, lighted tube with a tiny camera attached is inserted into the rectum and passed into the colon. The inside of the entire colon and rectum are examined. Polyps and abnormal tissue will be removed and examined under a microscope. For most people, this is the standard test for examining the colon and rectum.
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A virtual colonoscopy is a type of CT scan that takes detailed images of the rectum and colon. It does not require the insertion of a tube into the colon. Some of the benefits of a virtual colonoscopy include:
- Does not require the introduction of firm tubes as in endoscopy and barium enema
- No risk of possible injury to the bowel
- Sedation is not needed, recovery time is shorter
- Transportation to and from the procedure is not needed
However, if there is any suspicious-looking tissue, a colonoscopy will have to be done to remove it.
Diagnosis of Colorectal Cancer
Colorectal cancer may be suspected based on tests above. A biopsy will confirm cancer is present. A biopsy is a tissue sample that is removed from the colon or rectum. After removal, the sample is examined under a microscope. This is the only way to confirm a diagnosis.
Staging of Colorectal Cancer
Results from completed tests and new tests will help determine the stage of cancer. Staging is used to determine the prognosis and treatment plan. Factors that play a role in staging include how far the original tumor has spread, whether lymph nodes are involved, if cancer has spread to other tissue, and microscopic cellular or genetic details.
Tests that may help determine colorectal cancer stage:
- Blood tests
- Microscopic evaluation of tissue samples—to look for genetic characteristics.
- Imaging tests—to help determine how deep the tumor has moved into the layers of the colon, rectum, or nearby structures. They may also help to determine if there are any metastatic growths in other areas of the body. Imaging tests may include:
Stages of Colorectal Cancer
The colon and rectal walls are made of up 4 layers, the innermost mucosa, the submucosa, a thicker muscle layer, and a thin serosa. The location and depth of the tumor is important in staging. Colorectal cancer is staged from 0-IV.
- Stage 0—Carcinoma in situ —Abnormal cells are found only in the innermost lining of the colon or rectal wall.
- Stage 1 —Cancer has spread from the innermost lining of the colon or rectal wall TO the submucosa AND/OR muscle layers.
- Stage 2A —Cancer has spread from the muscle layer of the colon or rectum TO the serosa, the outermost layer of the wall.
- Stage 2B —Cancer has spread THROUGH the serosa of the colon or rectal wall, BUT not to any nearby organs.
- Stage 2C —Cancer has spread THROUGH the serosa of the colon or rectal wall TO nearby organs.
- Stage 3A —Cancer has spread TO the submucosa and possibly to the muscle layer of the colon or rectal wall AND to 1-3 lymph nodes or in the tissues next to the lymph nodes OR cancer has spread to the submucosa AND to 4-6 lymph nodes.
- Stage 3B —Cancer has spread THROUGH the muscle layer TO the serosa of the colon or rectal wall, BUT not to nearby organs AND to 1-3 lymph nodes or in the tissues next to the lymph nodes OR cancer has spread TO the muscle layer or serosa of the colon or rectal wall AND 4-6 lymph nodes OR cancer has spread THROUGH the mucosa TO the submucosa or muscle layer of the colon or rectal wall AND 7 or more lymph nodes.
- Stage 3C —Cancer has spread THROUGH the serosa of the colon or rectal wall, BUT not to nearby organs AND in 4-6 lymph nodes OR cancer has spread through the muscle layer of the colon or rectal wall, BUT not to nearby organs AND in 7 or more lymph nodes OR cancer has spread through the serosa of the colon or rectal wall AND nearby organs AND in 1 or more lymph nodes or in the tissues next to the lymph nodes.
- Stage 4 —Cancer has spread to other parts of the body through the lymph and blood streams. The most common sites for metastatic colorectal cancer are lymph nodes in other parts of the body, the lungs, liver, or other organs in the abdominal and pelvic cavities.
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Last reviewed December 2019 by Mohei Abouzied, MD Last Updated: 2/27/2020