Colon Polyps


What Is It?

Colon polyps are growths of tissue that erupt from the mucous membrane on the interior of the large intestine. Some polyps take the form of bulbous protrusions on the end of a tubelike stalk, somewhat like a mushroom. Others appear as bumps that lie flat against the intestinal wall. There are several types of polyps. Most are benign, but one type, the adenomatous polyp, is associated with changes (called mutations) in the DNA of the lining of the colon. These mutations can progress into colon cancer. The larger the polyp, the greater the chance that it contains cancerous cells. For a polyp larger than 1 inch in diameter, there is a 10-percent likelihood it is cancerous. Flat polyps are more prone to becoming cancerous than mushroom-shaped ones.

No one knows exactly what causes these growths to occur, although some people are born with a genetic tendency to develop multiple polyps. Inherited conditions such as familial adenomatous polyposis and Gardner’s syndrome can cause hundreds of polyps to grow in the colon and rectum. Without surgery to remove the affected section the intestine, it is almost certain that at least one of these polyps will turn into cancer by middle age. These two conditions are rare. Most adults are at risk of developing fewer polyps later in life, but are still at risk for complications.


Many times, people are not aware they have colon polyps because there are no symptoms. Larger growths can bleed, causing blood in the stool. Sometimes a person can experience fatigue and other symptoms of anemia from bleeding polyps. Occasionally, polyps can grow so large that they block the intestine or, rarely, cause diarrhea.


Your doctor may use one or more of the following tests to confirm the existence of colon polyps:

  • Digital rectal exam — The doctor inserts a gloved-finger into the rectum to check for unusual growths or formations. This can only detect polyps in the rectum, the lower few inches of the bowel.
  • Fecal occult blood test — A sample of stool is examined for minute traces of blood, an indication of polyps.
  • Sigmoidoscopy — A thin, lighted tube fitted with a video camera is inserted into the colon through the rectum allowing the doctor to examine the area for polyps. Small polyps can be removed through the scope.
  • Colonoscopy — A longer version of the instrument used in sigmoidoscopy is used to visualize the entire length of the colon. This is the only test that examines all the areas where cancers may grow. Small polyps can be removed through the scope.
  • Barium enema —A chalky liquid is injected into the colon through the rectum, and then X-ray images are taken of the intestine. Air also may be inserted to expand the colon and allow the area to be seen better.

Expected Duration

If a polyp is not removed, it will continue to enlarge. It usually takes many years for a polyp to grow to a size at which it could be potentially cancerous. About one-third of adenomatous polyps will progress to cancer in three to five years if undetected or ignored.


The danger from polyps is that most cases of colon cancer spring from these growths. You can lower your chances of developing cancerous polyps in the following ways:

  • Increase your consumption of fruits, vegetables and whole grains
  • Limit your intake of high-fat animal foods
  • Get at least 30 minutes of physical exercise on most days
  • Maintain a healthy weight. Extra fat, especially around the waist alters your metabolism and increases your chances of developing colon and rectal cancer.

In addition, evidence also suggests that doing the following may lower colon-cancer risk:

  • Taking a multivitamin daily — Extra folic acid in multivitamins may be the key.
  • Increasing your intake of calcium — The extra calcium can come from increased intake of low-fat dairy products or calcium supplements as advised by your doctor.
  • Taking aspirinlike drugs — In several studies, people who used aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) on a regular basis had a 40-percent to 50-percent lower chance of developing adenomatous polyps or colorectal cancer. Because of side effects of these drugs, taking them every day just to prevent colon cancer is not advised if your cancer risk is average.
  • Using hormone-replacement therapy — While the risk of colon cancer may be reduced by 30 percent to 40 percent in those who take estrogen after menopause, a woman considering this option should talk to her doctor about her particular risks because of new research about the long-term consequences of HRT use.
  • Quitting smoking — Colon cancer risk is increased by smoking cigarettes.

Since the incidence of colon cancer increases with age, people over 50 should have a fecal occult blood test, and/or a flexible sigmoidoscopy every five years. Alternatively, your doctor may recommend a total colon examination every 10 years. If you have a hereditary condition that causes the overgrowth of polyps in the large intestine, you should begin frequent examinations at puberty. You also may want to consider complete removal of the colon since there is a high likelihood of developing colon cancer by age 40. If you choose against this option, you should undergo an endoscopic exam of your colon every one to two years.


Polyps are removed surgically. Often, the doctor can remove polyps found during a colonoscopy at the time. This is done by cutting the polyp from the wall of the colon using an electrical current passed through a wire loop at the end of the colonoscope. Sometimes, open surgery through the abdomen is necessary to remove polyps. For cancerous polyps, surrounding tissue or a section of the colon may be removed as well.

When To Call A Professional

You should call immediately for advice if you develop rectal bleeding. You also should see your doctor regularly for routine colon examinations after age 50. People with a family history of colon cancer, familial adenomatous polyposis or Gardner’s syndrome should begin screening earlier.


While it is estimated that 30 percent of middle-aged and older people have colon polyps, less than 1 percent of all polyps ever becomes cancerous. For people who catch and treat colon cancer early, the five-year survival rate is 90 percent. If the cancer has reached the lymph nodes, the chance of survival drops to 65 percent. When the cancer has spread to distant parts of the body, the likelihood of living more than five years drops to 8 percent.


Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.