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What Is the Colon?

The colon is part of the digestive system. Food moves from the mouth to the stomach. Several hours later, it moves into the intestines, first the small intestine and then the large intestine. After digestion of food is finished, what’s left leaves the body as waste (stool) through the rectum. The colon is the last part of the large intestine, just before the rectum.

What Is Colon Cancer?

Colon cancer is a tumor in the colon. It is the most common cancer of the digestive tract. Other names are adenocarcinoma of the colon and colorectal cancer (often the lower rectum and sigmoid part of the colon are involved). The cancer can also be found in the first part of the colon (cecum). Colon cancer can also spread (metastasize) to other parts of the body.

Colon cancer usually starts as a small growth (polyp) on the surface of the colon. Some polyps are harmless, but some can turn into cancer.

Colon cancer tends to run in families. If you have a strong family history of colon cancer, you should discuss with your health care provider genetic testing done with blood tests to look for genetic changes that predispose to rare hereditary colon cancers known as familial adenomatous polyposis (FAP) and Lynch syndrome.

What Are Symptoms of Colon Cancer?

Symptoms to be aware of are a change in bowel habits, such as constipation or diarrhea, a change in stool size (e.g., pencilthin) or stool appearance (e.g., black and tarry), rectal bleeding, and abdominal pain.

Sometimes no symptoms are present, but iron deficiency anemia from long-term blood loss may occur.

Early diagnosis is critical because undetected or untreated cancer usually spreads through the intestine wall into neighboring areas and into the liver. Sometimes it can also spread to lungs and bones.

How Is Colon Cancer Diagnosed?

The health care provider will do a complete physical examination, including a digital rectal examination (DRE), and take one or more stool samples. These samples are analyzed for any occult (hidden) blood. This testing can find bleeding in the intestine, but results can be inaccurate because certain medicines or red meat may produce positive results that are really normal (false-positive results).

The doctor also looks inside the colon with a flexible tube called a colonoscope. This scope is passed through the rectum to see the whole colon. The doctor can see problem areas and biopsy (take samples of) these areas and remove any polyps. The samples are studied under a microscope to look for cancerous cells. Other tests, such as computed tomography (CT), of the abdomen and pelvis may be done to see whether cancer has moved to other parts of the body.

A newer screening test involves using CT only for the intestine (CT colonography). This test is also called virtual colonoscopy. For this test, compressed air is pumped into your rectum through a tube and then a picture is taken of your colon. For this test you will also have to take laxatives the day before to clean out the colon. Any possible problem areas found by CT colonography will need a follow-up colonoscopy to see whether they are cancerous.

Newer screening methods check for cancer cells by detecting the presence of abnormal DNA in stool samples (fecal DNA tests).

DOs and DON’Ts in Diagnosing and Preventing Colon Cancer:
  • DO realize the importance of colon screening for everyone, starting at age 50 or earlier for people who have family members with colon cancer.
  • DO follow your doctor’s advice.
  • DO eat a high-fiber diet.
  • DO watch your weight.
  • DO exercise. Exercising can improve your overall health.
  • DON’T forget the importance of screening.
  • DON’T smoke.

Contact the following sources:

  • Colon Cancer Alliance
    Tel: (877) 422-2030
  • American Cancer Society
    Tel: (800) ACS-2345
  • American College of Gastroenterology
    Tel: (703) 820-7400

Copyright © 2016 by Saunders, an imprint of Elsevier, Inc.

Ferri’s Netter Patient Advisor