Diagnosis of Colorectal Cancer
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Your doctor will first review your medical history. A complete medical exam will be done. One or more of the following tests may be done:
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. About half of colon cancers can be detected in this way, especially if a test for occult blood is done at the same time. It is not a good idea to ask your doctor to skip your rectal exam during a routine checkup. It is a good idea to agree to having your stool tested for occult blood.
]]>X-ray]]> of the Large Intestine—An x-ray will provide a picture to help identify the presence of polyps. This is often done with the addition of contrast medium (barium). Barium will help to create better pictures of the surface of the bowel.
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.
Endocsopy—In endocscopy, 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.
Polypectomy—The removal of a polyp or polyps during sigmoidoscopy or colonoscopy.
]]>Biopsy]]>—A tissue sample from a polyp is removed from the body. It is sent to a pathologist for examination.
]]>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 Colonscopy—A type of CT scan that uses computer software along with CT imaging to examine to 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 do 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
Some studies indicate that virtual colonscopy is almost as effective as endoscopy for determining the presence of polyps. However, if a polyp is found by virtual colonoscopy, a second procedure is necessary to remove and examine it. Virtual colonoscopy is not appropriate if you have a higher risk for developing polyps. With conventional endoscopy, the biopsy can usually be done at the same time. Virtual colonscopy is not available everywhere.
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 depend on the location, size, and stage of the cancer and your general health.
Additional tests to determine the cancer’s stage may include:
- Urine and blood tests
- Additional physical exam
- X-rays of various parts of the body, including lungs, bladder, kidneys, lymph nodes
- Barium enema to check the colon and rectum
- ]]>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.
- ]]>PET scan]]>—This is a relatively new 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 (also called Dukes’ A colon cancer)—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 (also called Dukes’ B colon cancer)—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 bean-shaped structures found throughout the body that help filter lymph and fight infection and disease.
- Stage III (also called Dukes’ C colon cancer)—Cancer has spread to nearby lymph nodes, but not to other parts of the body.
- Stage IV (also called Dukes’ D colon cancer)—Cancer has spread to other parts of the body, such as the liver and lungs.
- Recurrent—Recurrent cancer means that the cancer has returned after undergoing treatment.
National Cancer Institute website. Available at: http://www.cancer.gov/ .
Last reviewed February 2009 by ]]>Daus Mahnke, MD ]]>
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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