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Diagnosis of Colorectal Cancer
Tests Used to Identify Potential Colorectal Cancers
- 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.
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- 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
Staging of Colorectal Cancer
- 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.
- 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.
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.
- Reviewer: Mohei Abouzied, MD
- Review Date: 05/2014
- Update Date: 05/17/2014