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What is a colonoscopy?

A colonoscopy is an exam of the colon (large intestine, or bowel) with a slim, flexible, lighted tube called a colonoscope. Your healthcare provider can use the scope to look at the full length of the inside of your colon.

When is it used?

Colonoscopy is the most direct and complete way to see the entire lining of the colon. It is usually done for one of the following reasons:

  • Prevention and early detection of cancer. A colonoscopy can help your provider find and remove growths (polyps) before they become cancerous. It can also allow your provider to find cancerous growths early, when the cancer is easier to cure.

    If you are between 50 and 75 years old, your healthcare provider may recommend that you have a colonoscopy at least every 10 years. If you have a personal or family history that increases your risk, your provider may recommend that you start having the test at an earlier age and have the test more often. In some cases, the test may be recommended for people older than 75.

  • Diagnosis of illness. If you have symptoms of illness that your provider has not been able to explain, you may have this test to try to find the cause of your symptoms. For example, you may be having unexplained abdominal pain or abnormal bowel movements. Your provider can check for inflammation of the bowel lining or infected pockets (diverticula) in the bowel wall.

An alternative to the colonoscopy procedure described here is a virtual colonoscopy. A virtual colonoscopy is a way to look for signs of precancerous growths (polyps), cancer, and other diseases of the large intestine without putting a scope into the colon. Images of the colon are taken using computerized tomography (CT). A computer puts a series of X-ray images together to create an animated 3-D view of the inside of the large intestine. Preparation of the bowel is the same as for a regular colonoscopy. If a polyp or cancer is seen, you will need to schedule a regular colonoscopy to obtain tissue (biopsy) for diagnosis. Virtual colonoscopy has not been accepted as a screening method by all major national guideline groups. Also, your insurance company may not pay for the procedure.

How do I prepare for the exam?

If you need a minor pain reliever in the week before the procedure, choose acetaminophen rather than aspirin, ibuprofen, or naproxen. This helps avoid extra bleeding during the procedure. If you are taking daily aspirin for a medical condition, ask your provider if you need to stop taking it before the procedure. If you have been taking Coumadin (a blood thinner), you will have to stop it several days before the exam. Unless otherwise instructed, you can keep taking any of your other usual medicines.

Your healthcare provider will give you written instructions on how to clear bowel movements from the colon.

  • You will probably be asked to not eat any solid food for 24 to 48 hours before the exam.
  • You should have only clear liquids 12 to 24 hours before the exam. Clear liquids are water, broth, apple or white grape juice, tea or coffee (no milk or cream), and soda. Gelatin in any color but red may also be eaten.
  • You will be asked to take a liquid laxative. You may be told to give yourself a home enema a few hours before your exam. This will clear stool from the bowel. Be sure to complete this bowel preparation. The exam may not be possible if the colon still has stool in it.

Drink plenty of clear liquids during the bowel prep to avoid dehydration. It is helpful to drink liquids that help replace the electrolytes (potassium and sodium) you lose during the prep. For example, you can drink sports drinks in any color but red.

The test takes 20 to 30 minutes. However, you will need to plan on being at the healthcare provider's office or clinic for a total of about 1 and a half to 2 hours for check-in, the exam, and recovery. Find someone to drive you home after the exam.

What happens during the procedure?

A colonoscopy may be done in the healthcare provider's office or in an outpatient clinic.

Just before your exam, you may be given a sedative, which will help relax you. You may be given this medicine with a needle in your vein (IV).

You will lie on a table on your side with your knees bent and drawn up to your stomach. This position makes it easier for your healthcare provider to pass the colonoscope into your anus and rectum and up into your colon.

Your provider can view the images of the colon on a TV monitor. As the scope is passed through your colon, air is pumped into the colon so your provider can see as much of the walls of the colon as possible. This air may make you feel bloated and give you cramps.

If your provider sees anything abnormal during the exam, he or she may take small samples of tissue through the colonoscope for lab tests. It may be possible to remove any abnormal areas, polyps, or small tumors from the colon through the colonoscope. This may help you avoid having another procedure to remove them.

What happens after the procedure?

After the scope is removed, you may rest until you are awake and alert enough to be driven home. You should plan on continuing to rest for a few hours after you get home. It is normal to have gas and mild cramps for a few hours after the exam. After resting you should feel like eating a normal diet again. Be sure to drink lots of fluids after the test.

If polyps or other tissue is removed, you may notice a small mount of blood in your stools for a short time.

Before you have the exam, ask your healthcare provider when and how you will be informed of the results. Someone may call you or you may need to call or make a follow-up appointment to get the results.

What are the benefits of this procedure?

This procedure helps your healthcare provider diagnose problems in the colon. For some problems, such as cancer, treatment is more effective when the problem is found early.

What are the risks associated with this procedure?

Risks include:

  • some pain or swelling in your lower abdomen if air was pumped into your intestine during the procedure (this will last until your body passes the extra air shortly after the procedure)
  • damage to the colon (perforation) from the colonoscope and possible infection, which may require surgery for repair
  • bleeding inside the colon, which also may need surgery

When should I call my healthcare provider?

Call your provider right away if:

  • You have severe abdominal pain or rectal bleeding.
  • Pain or symptoms you had before the procedure become worse.

Call during office hours if:

  • You have questions about the procedure or its results.
  • You want to make another appointment.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIA File diag5111.htm Release 13/2010

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