Colonoscopy is a test that allows your doctor to look at the inner lining of your large intestine (rectum and colon). He or she uses a thin, flexible tube called a colonoscope to look at the colon. A colonoscopy helps find ulcers, colon polyps, tumors, and areas of inflammation or bleeding. During a colonoscopy, tissue samples can be collected (biopsy) and abnormal growths can be taken out. Colonoscopy can also be used as a screening test to check for cancer or precancerous growths in the colon or rectum (polyps).
The colonoscope is a thin, flexible tube that ranges from 48 in. (122 cm) to 72 in. (183 cm) long. A small video camera is attached to the colonoscope so that your doctor can take pictures or video of the large intestine (colon). The colonoscope can be used to look at the whole colon and the lower part of the small intestine. A test called sigmoidoscopy shows only the rectum and the lower part of the colon.
Before this test, you will need to clean out your colon (colon prep). Colon prep takes 1 to 2 days, depending on which type of prep your doctor recommends. Some preps may be taken the evening before the test. For many people, the prep for a colonoscopy is more trying than the actual test. Plan to stay home during your prep time since you will need to use the bathroom often. The colon prep causes loose, frequent stools and diarrhea so that your colon will be empty for the test. The colon prep may be uncomfortable and you may feel hungry on the clear liquid diet. If you need to drink a special solution as part of your prep, be sure to have clear fruit juices or soft drinks to drink after the prep because the solution tastes salty.
Colonoscopy is one of many tests that may be used to screen for colon cancer. Which screening test you choose depends on your risk, your preference, and your doctor. Talk to your doctor about what puts you at risk and what test is best for you.
For more information on screening tests for colon cancer, see:
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Why It Is Done
Colonoscopy is done to:
How To Prepare
Before you have a colonoscopy, tell your doctor if you:
You may be asked to stop taking aspirin products or iron supplements 7 to 14 days before the test. If you take blood-thinning medicines regularly, discuss with your doctor how to manage your medicine.
You will be asked to sign a consent form that says you understand the risks of colonoscopy and agree to have the test done. Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
Before this test, you will need to clean out your colon. The following information gives you a general idea of the preparation for a colonoscopy. Your doctor will give you specific instructions before your test.
Arrange to have someone take you home after the test because you may be given a medicine (sedative) to help you relax before the test.
How It Is Done
Colonoscopy may be done in a doctor's office, clinic, or a hospital. The test is most often done by a doctor who works with problems of the digestive system (gastroenterologist). The doctor may also have an assistant. Some family doctors, internists, and surgeons are also trained to do colonoscopy.
During the test, you may get a pain medicine and a sedative put in a vein in your arm (IV). These medicines help you relax and feel sleepy during the test. You may not remember much about the test.
You will need to take off most of your clothes. You will be given a gown to wear during the test.
You may lie on your left side with your knees pulled up to your belly. The doctor will gently put a gloved finger into your anus. Then he or she will put the thin, flexible colonoscope in your anus and move it slowly through your colon. The doctor can look at the lining of the colon through the scope or on a computer screen hooked to the scope.
You may feel the need to have a bowel movement while the scope is in your colon. You may also feel some cramping. Breathe deeply and slowly through your mouth to relax your belly muscles. This should help the cramping. You will likely feel and hear some air escape around the scope. There is no need to be embarrassed about it. The passing of air is expected. You may be asked to change your position during the test.
Your doctor will look at the whole length of your colon as the scope is gently moved in and then out of your colon.
View a slideshow about how a colonoscopy is done.
The doctor may also use tiny tools, such as forceps, loops, or swabs, through the scope to collect tissue samples (biopsy) or take out growths. Usually, people do not feel anything if a biopsy is done or if polyps are taken out.
The scope is slowly pulled out of your anus and the air escapes. Your anal area will be cleaned with tissues. If you are having cramps, passing gas may help relieve them.
The test usually takes 30 to 45 minutes, but it may take longer, depending upon what is found and what is done during the test.
After the test, you will be watched for 1 to 2 hours. When you are fully awake, you can go home. You will not be able to drive or operate machinery for 12 hours after the test. Your doctor will tell you when you can eat your normal diet and do your normal activities. Drink a lot of fluid after the test to replace the fluids you may have lost during the colon prep but do not drink alcohol.
If you received a sedative during the test, do not drive, operate machinery, or sign legal documents for 24 hours after the test. Arrange to have someone drive you home after the test.
How It Feels
This test can be uncomfortable and you may feel embarrassed. The colon prep will cause diarrhea and cramping which may make you use the bathroom often.
During the test, you may feel very sleepy and relaxed from the sedative and pain medicines. You may have cramping or feel brief, sharp pain when the scope is moved or air is blown into your colon. As the scope is moved up the colon, you may feel the need to have a bowel movement and pass gas. If you are having pain, tell your doctor.
The suction machine used to remove stool (feces) and secretions may be noisy but does not cause pain.
You will feel sleepy after the test for a few hours. Many people say they do not remember very much about the test because of the sedative.
After the test, you may have bloating or crampy gas pains and may need to pass some gas. If a biopsy was done or a polyp taken out, you may have traces of blood in your stool (feces) for a few days. If polyps were taken out, your doctor may instruct you to not take aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) for 7 to 14 days.
There is a small chance for problems from a colonoscopy. The scope or a small tool may tear the lining of the colon or cause bleeding.
After the test
After the test, call your doctor immediately if you:
Colonoscopy is a test that allows your doctor to look at the inner lining of your large intestine (rectum and colon). If a sample of tissue (biopsy) was collected during the colonoscopy, it will be sent to a lab for tests.
Your doctor may be able to tell you the results immediately after the procedure. Other test results are ready in 2 to 4 days. Test results for certain infections may be ready in several weeks.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
What To Think About
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