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Colonoscopy
What is the test?In colonoscopy, an endoscope is passed through the anus and all the way up through the entire colon (also called the large intestine) so that the doctor can see any abnormalities. This screening test is used to find early cancers and potentially cancerous polyps (growths on the colon lining). With colonoscopy, the doctor can immediately remove polyps and take biopsies of suspicious tissue. You should have regular screening for colon cancer starting at age 50, using either colonoscopy or sigmoidoscopy . Many people wonder which test is right for them. How do I prepare for the test?For the doctor to get a clear look at the lining of your large intestine, it's important that you drink only clear liquids, such as juice or broth, the night before the procedure. During the afternoon and evening before the procedure, you need to clear your bowels by drinking a fluid that will help flush them out. Because this fluid will cause you to go to the bathroom frequently, it's best to stay home after you take it. Some doctors recommend a laxative instead of this liquid, or they recommend using both. Your doctor may recommend an enema 30-60 minutes before the colonoscopy, so you have one last bowel movement. For many people who undergo a colonoscopy, the "clean-out procedures" before the test are more unpleasant than the test itself. Avoid taking aspirin or other NSAIDs for several days before the test to reduce the risk of bleeding in case a biopsy must be taken or a polyp removed. Also, let your doctor know if you're taking a blood-thinning medicine. In addition, tell your doctor if you've had any abdominal surgery and if you're taking insulin. Since you must limit what you eat on the day before the colonoscopy, if you take your usual dose of insulin, your blood sugar might become dangerously low. What happens when the test is performed?You may receive a sedative through an IV (see "Sedatives and anesthesia," page 8). You wear a hospital gown for the test and lie on your side on a table.After putting on a glove and applying some clear jelly to the outside of it, the doctor feels the inside of your rectum with a finger. He or she gently inserts one end of the colonoscope into your rectum. The colonoscope is a type of endoscope that is about half an inch wide and a little more than 5 feet long so it can reach the entire length of your large intestine (see "Endoscopes," page 27). The doctor fills your intestine with air so that the camera at the end of the colonoscope gets a good view. If you didn't receive a sedative, you might feel a cramplike pain - similar to the cramping you might get when you have gas-when air is pumped into your colon. Images of the interior of your colon appear on a video screen. If your doctor sees a suspicious place on the bowel lining, he or she might use some small clippers on the end of the scope to take a biopsy. If your doctor sees a polyp, he or she removes it with a loop of wire pushed through the colonoscope. The doctor tightens the loop around the polyp's stem and sends a brief electric current through the wire to burn the stem and separate it from your intestine. This process isn't painful because there are few nerve endings in the stem of the polyp. The polyp can be removed using vacuum pressure on the colonoscope or another tool on the end of the scope.When the doctor is finished, he or she sucks the extra air out of your intestine and gently pulls the colonoscope out. The test usually takes 20-90 minutes, depending on whether any polyps are removed. What risks are there from the test?The risks are small, although they are greater for this test than with sigmoidoscopy. If you had a biopsy, you might have a small amount of bleeding after the procedure. Some bleeding complications require another colonoscopy or surgery. It's also possible to have an adverse reaction to the sedative- for example, an allergic reaction or even heart or breathing complications. You may also feel some bloating or pain for a few days after the procedure. Must I do anything special after the test is over?Because you have been given a sedative, arrange for a friend or family member to drive you home afterward. Call your doctor if you have more than half a cup of bleeding from the rectum or if you have severe abdominal pain, fever, or chills. In rare cases, polyps that are separated from the colon wall cannot be pulled out of the colon with the scope. If this happens, your doctor might ask you to take a laxative and use a strainer to catch the polyp when you have a bowel movement, so it can be examined in the laboratory. How long is it before the result of the test is known?Your doctor can tell you the results of the exam immediately afterward. If biopsy samples or polyps were removed, they are examined in a laboratory for cancer and other diseases. It may take a few days for your doctor to get the lab report. |
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