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Diagnosis of Colorectal Cancer

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Your doctor will first review your medical history. A complete medical exam will be done. Your doctor may recommend different tests in order to identify tumors and confirm diagnosis.

Tests Used to Identify Potential Colorectal Cancers

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. Rarely colon cancers can be detected in this way.

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 should be followed up with a more specific test such as endoscopy. A negative result does not guarantee that colorectal cancer is not present.

Endoscopy—In endoscopy, the doctor inserts a flexible tube into the bowel. The tube contains a camera that is used to examine the interior surface of the bowel. The doctor will look for irregularities, such as polyps. Two types of endoscopy 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.
  • Colonoscopy —A thin, lighted tube with a tiny camera attached is inserted into the rectum. The inside of the entire colon and rectum are examined. If a polyp or abnormal tissue is discovered, it may be removed and reviewed for further testing. For most patients, this is the standard for examining the colon.
Colonoscopy Procedure
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Polypectomy—The removal of a polyp or polyps during sigmoidoscopy or colonoscopy.

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.

Virtual Colonoscopy—A type of CT scan that uses computer software along with CT imaging to examine the colon for polyps. A rubber catheter is used to introduce air into the colon. This procedure is still being studied. 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

Tests to Confirm Diagnosis

Diagnosis of colorectal cancer is done by biopsy. A biopsy is a tissue sample that is removed from the colon or rectum. After removal, the sample is sent to a pathologist for examination.

Staging of Colorectal Cancer

Staging is a careful attempt to determine whether the cancer has spread from the inner lining of the colon. If the cancer has spread, staging will also help determine what body parts are affected.

If cancer is found, the prognosis and treatment depends on the location, size, and stage of the cancer, and your general health.

Additional tests to determine the cancer’s stage may include:

  • Blood tests
  • X-rays of various parts of the body
  • CT scan—This is a series of x-rays put together by a computer to make detailed pictures of areas inside the body.
  • Ultrasonography—In this procedure, sound waves are bounced off body tissues. The echoes produce a picture.
  • MRI scan—A magnet linked to a computer is used to create detailed pictures of areas inside the body.
  • Positron emission tomography (PET) scan—This is a way of looking for small amounts of cancer that may have spread or not responded to treatments. A radioactive sugar molecule is injected into your vein. The scan is taken a few hours later. Tumors use sugar faster than normal tissues. The radioactive tracer attached to the sugar molecule helps identify the tumor cells.

If colorectal cancer is diagnosed, the following staging classification is used to identify how and where the cancer has spread.

  • Stage 0, also called carcinoma in situ—In this stage, abnormal cells are found only in the innermost lining of the colon.
  • Stage I—Cancer has spread beyond the innermost lining of the colon to the second and third layers and involves the inside wall of the colon. However, it has not spread outside the colon wall.
  • Stage II—Cancer has spread beyond the muscular walls of the colon and has spread as far as the fat or thin skin that surrounds the colon and rectum. It has not yet gone to the lymph nodes. Lymph nodes are structures found throughout the body that help filter lymph and fight infection and disease.
  • Stage III—Cancer has spread to nearby lymph nodes, but not to other parts of the body.
  • Stage IV—Cancer has spread to other parts of the body, such as the liver and lungs.

Revision Information

  • Colon and rectal cancer. National Cancer Institute website. Available at: http://www.cancer.gov/cancertopics/types/colon-and-rectal. Accessed May 14, 2013.

  • Colorectal cancer. American Cancer Society website. Available at: http://www.cancer.org/acs/groups/cid/documents/webcontent/003096-pdf.pdf . Updated January 17, 2013. Accessed May 14, 2013.

  • Colorectal cancer. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php. Updated May 3, 2013. Accessed May 14, 2013.