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
If you are having bowel or other symptoms, your doctor may conduct certain tests to identify abnormalities. These may include:
Digital rectal exam
—Your doctor will insert a lubricated, gloved finger into the rectum. The doctor will check the rectum for lumps or abnormal areas.
The test is painless, though you may feel some pressure.
Fecal occult blood test
—A small sample of stool is placed on a special card. It is then tested by a lab for hidden blood.
Blood can be present in the stool for many reasons. Colorectal cancer will not always cause blood in the stool. If positive, the test will be followed up with additional tests. 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 be elevated in the presence of cancer. 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 the presence of tumors. They can also help assess their size and location. Some tests use contrast material to highlight structures so images are more clear and detailed. Imaging tests may include:
Barium enema—A barium liquid is put into the rectum by way of the anus. Barium is a metallic compound that helps highlight the image of the lower gastrointestinal tract on an x-ray.
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.
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
Diagnosis of colorectal cancer is confirmed with a biopsy. 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
If colorectal cancer is confirmed, results from completed tests and new tests will help determine the stage of cancer. Staging is used to identify characteristics of the tumor that will help 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 details.
Tests that may help determine colorectal cancer stage:
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:
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 I—Cancer has spread from the innermost lining of the colon or rectal wall TO the submucosa AND/OR muscle layers.
Stage IIA—Cancer has spread from the muscle layer of the colon or rectum TO the serosa, the outermost layer of the wall.
Stage IIB—Cancer has spread THROUGH the serosa of the colon or rectal wall, BUT not to any nearby organs.
Stage IIC—Cancer has spread THROUGH the serosa of the colon or rectal wall TO nearby organs.
Stage IIIA—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 IIIB—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 IIIC—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 one or more lymph nodes or in the tissues next to the lymph nodes.
Stage IV—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.
Colorectal cancer. American Cancer Society website. Available at: http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf. Accessed January 3, 2017.
Colorectal cancer. Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/gastrointestinal-disorders/tumors-of-the-gi-tract/colorectal-cancer. Updated July 2014. Accessed January 3, 2017.
Stages of colon cancer. National Cancer Institute website. Available at: https://www.cancer.gov/types/colorectal/patient/colon-treatment-pdq#section/_112. Updated June 30, 2016. Accessed January 3, 2017.
Stages of rectal cancer. National Cancer Institute website. Available at: https://www.cancer.gov/types/colorectal/patient/rectal-treatment-pdq#section/_111. Updated June 30, 2016. Accessed January 3, 2017.
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