How to Find Colon Polyps Early

You can't see them or feel them, but they're definitely something you need to pay attention to.

Polyps are mushroom-like growths in the lining of your large intestine (colon) and your rectum. Why are they a problem? Some -- though not all -- can turn into colorectal cancer.

To keep this disease away, it's important to find polyps early. Since they usually don't cause symptoms, your best bet is to get a screening test that can spot them.

You've got several choices. Which one you get -- and how often -- depends on your age and what kind of risk you've got for colorectal cancer. Experts say you should get your first test at age 45, but if you've got a family history of the condition, you may need to start earlier. Check with your doctor about what's right for you.

Colonoscopy

With this method, your doctor not only can find polyps, he can remove them at the same time.

About 1 to 3 days before the test, you'll go on a clear liquid diet and drink a laxative to clean out your colon. The colonoscopy takes about 30 minutes. Your doctor places a thin, bendable tube through your anus and into your colon and rectum -- the lower part of your large intestine. The tube has a camera at one end so your doctor can see any polyps there, plus tiny instruments to remove them.

Your doctor will give you medicine so that you're not awake while he does his job. If he finds any polyps, he'll send them to a lab to check for signs of cancer.

If you choose a colonoscopy as your screening test, the American Cancer Society suggests you get one every 10 years, but your doctor may ask you to come back earlier if he finds polyps.

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Flexible Sigmoidoscopy

Like a colonoscopy, this test uses a thin, lighted tube to show the inside of your colon and rectum and remove polyps.

The disadvantage is that your doctor can only see the lower part of your colon. A sigmoidoscopy may miss polyps that are higher up.

You don't need to do as much bowel prep for a sigmoidoscopy. The test takes about 20 minutes. Unlike a colonoscopy, you're awake while it's going on, but your doctor may suggest you take medicine that helps you relax.

If sigmoidoscopies are your choice to check for polyps, the American Cancer Society recommends you get them every 5 years.

CT Colonography

Also called a virtual colonoscopy, this test uses low-dose X-rays to take pictures inside your colon from many different angles. The scope is shorter than the one used in a colonoscopy.

You won't be asleep during a CT colonography, but you'll still have to drink a liquid diet and take laxatives to clean out your bowel a day or two beforehand. If the doctor finds polyps in your colon, you'll need a colonoscopy to remove them.

If you choose this test for screening, the American Cancer Society recommends having one every 5 years. 

FOBT (Guaiac-Based Fecal Occult Blood Test)

Polyps and colon cancers have delicate blood vessels on their surface that can break and leak blood into your bowel movements. An FOBT looks for tiny traces of this blood.

Your doctor will give you a kit to collect a sample of your bowel movement at home. You'll place it onto a special card. Then you'll bring it back to your doctor's office or send it to a lab. The card is covered with a chemical called guaiac, which changes color if there's blood.

If this is the screening test you use, the American Cancer Society says you should get one every year. If an FOBT picks up signs of blood, you may need to get a colonoscopy or other tests to find out what's going on.

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FIT (Fecal Immunochemical Test)

Just like the FOBT, this test looks for tiny amounts of blood in your bowel movement. It looks for proteins in blood called antibodies.

To take this exam, you'll also need to collect a sample of your bowel movement at home. Then you'll return it to your doctor's office or a lab to be tested. If you choose FIT as your screening method, you need to get it once a year.

If the exam shows a problem, your doctor will likely ask you to get a colonoscopy to check some more.

Stool DNA Test

This newer test looks for gene changes in colon cancer cells or polyps. As with FIT and the FOBT, you collect a sample of your bowel movement at home and then send it to a lab for DNA tests.

If a stool DNA test is the method you use to check for colon cancer, you should get it done every 3 years. If the results show anything amiss, you'll need a colonoscopy to check for and remove polyps.

How to Choose a Test

Go over all your colorectal cancer screening options with your doctor. There are pros and cons to the different tests.

You'll want to think about things like how much prep you need to do and whether you'll be awake or not during the exam. Also ask your doctor about any risks or side effects. And find out if you need to take a different kind of test, like a colonoscopy, if your first exam shows signs of trouble.

Whichever one you go with, make sure you keep up with your doctor's suggestions for regular testing. Routine checks for polyps can be lifesavers. You'll keep cancer away or catch it early, when it's easier to treat.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on July 10, 2018

Sources

SOURCES:

American Cancer Society: "American Cancer Society recommendations for colorectal cancer early detection;" "Frequently Asked Questions About Colonoscopy and Sigmoidoscopy;" "Stool DNA Testing for Colon Cancer;" and "Colorectal cancer screening tests."

American College of Gastroenterology: "Colon Polyps."

American Society of Clinical Oncology: "Fecal Occult Blood Tests."

CDC: "Colorectal Cancer Screening Tests."

Colorectal Cancer Association of Canada: "Introduction to Fecal Occult Blood Tests."

Massachusetts General Hospital: "Double-Contrast Barium Enema (DCBE)."

National Cancer Institute: "Tests to Detect Colorectal Cancer and Polyps."

National Institute of Diabetes and Digestive and Kidney Diseases: "Colonoscopy."

U.S. Preventive Services Task Force: "Final Recommendation Statement. Colorectal Cancer: Screening."

Mayo Clinic: "Fecal occult blood test."

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