Diagnosis of Colorectal CancerEn Español (Spanish Version)
Your doctor will first review your medical history, then give you a complete medical exam. One or more of the following tests may be performed:
Digital Rectal Exam—Your healthcare provider will examine the rectum for lumps or abnormal areas by inserting a lubricated gloved finger into the rectum. 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’s a good idea never to ask your physician to skip your rectal exam during a routine checkup and always 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) to permit better examination of the surface of the bowel.
Fecal Occult Blood Test—A small sample of stool is placed on a special card and tested by a lab for hidden blood. Blood can be present in the stool for many reasons, and it may not be present even in the face of colorectal cancer. If positive, the test should be followed up with a more specific test such as endoscopy, but if it is negative, it is not a guarantee that colorectal cancer is nor present.
Endocsopy—In an endoscopic procedure, the physician inserts a flexible tube into the bowel and uses it to examine the interior surface of the bowel for irregularities, such as polyps. This may be limited to the lower colon and rectum (sigmoidoscopy) or may visualize the entire bowel (colonoscopy).
Sigmoidoscopy—The doctor inserts a sigmoidoscope (thin, lighted tube with a tiny camera attached) into the rectum to view the inside of the lower colon and rectum for polyps, tumors, or abnormal growths.
Colonoscopy—A colonoscopy examines the inside of the entire colon and rectum using a thin, lighted tube with a tiny camera attached, which is inserted into the rectum. If a polyp or abnormal tissue is discovered during this exam, it may be removed and reviewed for further testing. A newer form of colonoscopy, available at some centers, involves swallowing a small digital camera, which then transmits images of the bowel for viewing. Still another technique under study is “virtual colonoscopy,” a type of sophisticated and detailed body scan that allows physicians to examine the bowel without having the patient undergo an invasive procedure. For most patients, however, the standard for examining the colon remains endoscopic (tube) colonoscopy.
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Polypectomy—This involves removal of a polyp or polyps during sigmoidoscopy or colonoscopy.
Biopsy—During a biopsy, the doctor removes a tissue sample from a polyp for examination by a pathologist.
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 more comfortable procedure, virtual colonoscopy is 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, but this procedure does not require the introduction of firm tubes (as do endoscopy and barium enema). Therefore, there is not the risk of possible injury to the bowel. You are not sedated, so recovery time is shorter. Additionally, you do not need to arrange for transportation to and from the procedure as with endoscopy.
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—making this test inappropriate 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, and, if it has, 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, and 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 curative treatments. A radioactive sugar molecule is injected into your vein and then radiographically evaluated a few hours later. Since 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 April 2007 by Barbara Harty-Golder, MD, JD
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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