Screening for colon cancer - Gastro Services and Facilities

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sigmoidoscopy"). Procedure — Sigmoidoscopy requires that the patient prepare by cleaning out the lower bowel. This usually involves consuming a clear liquid diet, laxatives, and using an enema shortly before the examination. During the procedure, a thin, lighted tube is advanced into the rectum and the left side of the colon to check for polyps and cancer. Biopsies (small samples of tissue) can be removed during sigmoidoscopy. The procedure may cause mild cramping; most people do not need sedative drugs and are able to return to work or other activities the same day. Effectiveness — Physicians who perform sigmoidoscopy can identify polyps and cancers in the descending colon and rectum with a high degree of accuracy. Studies suggest that sigmoidoscopy, performed as infrequently as every 5 to 10 years, reduces death from cancers in the lower half of the colon and rectum (the area directly examined) by two-thirds [2]. Risks and disadvantages — The risks of sigmoidoscopy are small. The procedure can create a small tear in the intestinal wall in about 2 per every 10,000 people; death from this complication is rare. A major disadvantage of sigmoidoscopy is that it cannot detect polyps or cancers located only in the right side of the colon. Additional testing — Finding polyps or cancers in the lower colon increase the likelihood of polyps or cancer in the remaining part of the colon. Thus, if sigmoidoscopy reveals polyps or cancer, colonoscopy may be recommended to view the entire length of the colon. Faecal occult blood test and sigmoidoscopy — Combined screening with a faecal occult blood test and sigmoidoscopy is a common practice and may be more effective than screening with either test alone [3]. Colonoscopy — Colonoscopy allows a physician to see the lining of the rectum and the entire colon. (See "Patient information: Colonoscopy"). Procedure — Colonoscopy requires that the patient prepare by cleaning out the the entire colon and rectum. This usually involves consuming a liquid that causes diarrhea temporarily. The patient is given a mild sedative drug before the procedure. During colonoscopy, a thin, lighted tube is used to directly view the lining of the rectum and the entire colon. Polyps and some cancers can be removed during this procedure. Effectiveness — Colonoscopy detects most small polyps and almost all large polyps and cancers [4]. Risks and disadvantages — The risks of colonoscopy are greater than those of other screening tests. Colonoscopy leads to serious bleeding or a tear of the intestinal wall in about 1 in 1,000 people. Because the procedure requires sedation, the person must be accompanied home after the procedure and the person should not return to work or other activities on the same day. Barium enema test — A barium enema test provides a detailed x-ray picture of the rectum and the entire colon. A more accurate version of the test, called double-contrast barium enema, is usually recommended.
Procedure — During a double contrast barium enema test, liquid barium is inserted into the rectum where it coats the inside of the colon. The barium is then drained out and the colon is filled with air. A thin layer of barium is left on the colon wall, which allows x-ray images to show a detailed view of the colon wall, including structural abnormalities such as polyps and cancers. Preparation for a barium enema including cleaning the colon by drinking a saline laxative. Some people experience mild cramping during the procedure. Sedative drugs are usually not necessary and most people can return to work or other activities after the test is completed. Effectiveness — The barium enema test detects about one-half of large polyps and about 40 percent of all polyps in the colon and rectum [5]. Most experts feel that screening with barium enema reduces the risk of dying from colorectal cancer, but this has not been definitively proven. Risks and disadvantages — The barium enema test is relatively safe compared with other screening tests for colorectal cancer. Additional testing — If a barium enema test reveals an abnormality, a colonoscopy is usually recommended. New tests — Several new screening tests for colorectal cancer are being developed and evaluated. These tests include improved faecal occult blood tests, faecal tests for genetic abnormalities linked to colorectal cancer, and a type of computed tomography (CT) scan called a virtual colonoscopy. These tests are still being studied, and they are not yet recommended for routine screening. The major advantages of virtual colonoscopy compared with traditional colonoscopy are that the procedure is safe and there is no need for sedation. However, if a worrisome polyp is found on virtual colonoscopy, a traditional colonoscopy will be needed to see the area and remove a tissue sample (biopsy). Additionally, the accuracy of virtual colonoscopy depends upon how it is performed; the test that is currently available may not be accurate enough for use as a screening test. Virtual colonoscopy, like traditional colonoscopy, requires cleaning out the entire colon. SCREENING PLANS — The screening plan that is recommended depends upon a person's risk of colorectal cancer. Average risk of colorectal cancer — People with an average risk of colorectal cancer should begin screening at age 50. The tests differ in features (effectiveness in preventing cancer, comfort, safety, cost, and convenience). No single screening test has been identified as the best test for all adults. The available options should be discussed with a clinician to develop a screening plan that will be followed. Some clinicians recommend a faecal occult blood test once per year and a sigmoidoscopy once every five years; a combination of these screening tests may also be recommended. Alternative screening plans include a colonoscopy once every 10 years or a double contrast barium enema every five years. If the results of one or more of these tests are abnormal, more frequent testing may be recommended. Increased risk of colorectal cancer — Screening plans for people with an increased risk may entail screening at a younger age, more frequent screening, and the use of more sensitive
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