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Diagnostic Tests - Flexible Sigmoidoscopy
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Flexible Sigmoidoscopy

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What is the test?

Sigmoidoscopy uses an endoscope to look inside the lower portion of the large intestine. The endoscope used for this test is about a half-inch wide and long enough to reach about two feet into the colon. A sigmoidoscopy can detect early cancers as well as polyps that could later become cancerous.

Sigmoidoscopy is an effective screening test for colon cancer if you have the procedure done every five years starting at age 50. Alternatively, you might choose to have a colonoscopy every 10 years to screen for colon cancer. In either case, it's wise to have a fecal occult blood test in the years you don't have a sigmoidoscopy or colonoscopy. A sigmoidoscopy is also useful for evaluating the cause of abdominal pain, blood in the stool, constipation, and diarrhea.

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How do I prepare for the test?

Your doctor might ask you to limit your dinner on the night before the test to clear liquids such as juice or broth. On the day of the procedure, you are given one or two enemas 30-60 minutes before the test to empty your bowels, enabling the doctor to get a clear look at your large intestine. If you suffer from constipation, your doctor might also ask you to use a laxative the night before the test. Try to avoid taking NSAIDs or blood thinners for several days before this test to reduce the risk of bleeding if any tissue needs to be biopsied. If you are on medications for diabetes, ask your doctor about ways to avoid hypoglycemia.

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What happens when the test is performed?

You wear a hospital gown for the procedure and lie on your side on a table. After applying some clear jelly to his or her gloved hand, the doctor feels the inside of your rectum with a finger, then gently inserts one end of the sigmoidoscope inside.

The doctor will fill your intestine with air, which often causes some pain similar to the cramping you might get when you have gas. As the camera on the scope transmits pictures to a video screen, your doctor watches for any suspicious lesions on your bowel lining. If one appears, he or she might use some small clippers on the end of the scope to take a tissue sample to check under the microscope. When the test is finished, the doctor vacuums the air out of your intestine and slowly removes the tube. The test usually takes 10-30 minutes.

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What risks are there from the test?

The risks are minimal. The chance of perforation is less than for a colonoscopy. A few people have a small amount of bleeding after the procedure if a biopsy has been taken.

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Must I do anything special after the test is over?

You should feel fine and be able to return to your regular activities immediately after the test. Call your doctor if you have more than light bleeding from the rectum or if you have continuing abdominal pain.

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How long is it before the result of the test is known?

Your doctor can tell you right away if there were any polyps or suspicious tissue in your colon. If biopsies are taken, it usually takes a few days until a laboratory examines them and gives your doctor a report. If your doctor finds polyps or cancer in your colon, you will probably need to have a similar but more comprehensive procedure called a colonoscopy done on another day. This is because polyps can be removed only during a colonoscopy. Moreover, discovery of polyps in the lower portion of the colon during sigmoidoscopy means there is a greater likelihood that polyps or cancer may exist in the rest of the colon - and this can be determined only with a colonoscopy.

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Answer health care questions about medical tests in this special report
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Medical Tests: A Practical Guide to Common Tests

Are you the type of person who panics when sent for even the most routine medical test? Medical Tests: A Practical Guide to Common Tests provides you with information about common screening and diagnostic medical tests so that you can breathe easier. You’ll learn why the test is needed, how to prepare for it, what happens during the test, and so much more. Now you can go in prepared!. Read more



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