Colorectal cancer consists of malignant cells found in the colon or rectum.

The colon and the rectum are parts of the large intestine, which is part of the digestive system. Because colon cancer and rectal cancer have many features in common, they are sometimes referred to together as colorectal cancer.

Excluding skin cancers, colorectal cancer is the third most common cancer in both men and women. The number of deaths from colorectal cancer has decreased, which is attributed to increased screening and polyp removal.

In adenocarcinoma, a type of cancer that accounts for more than 95 percent of colorectal cancers, early adenocarcinomas, or tumors, start as small polyps that continue to grow and turn into malignant tumors.

Risk Factors

The exact cause of most colorectal cancer is unknown, but there are several risk factors. Two that you can't control are age and race: most people who have colorectal cancer are older than 50, and African-Americans have the highest risk. Certain medical conditions can increase the risk for this cancer: polyps, which are benign growths on the wall of the colon or rectum; ulcerative colitis, or Crohn's disease; type 2 diabetes; and inherited syndromes such as familial adenomatous polyposis or hereditary nonpolyposis colon cancer. Health history makes a difference as well; the risk is higher for people who have had colorectal cancer or polyps and people with a strong family history of colorectal cancer or polyps. Last but not least, certain lifestyle habits can increase your risk. Colorectal cancer is often associated with a diet high in red and processed meats. Obesity, physical inactivity, heavy alcohol consumption, and smoking all play a role as well.

Colorectal Cancer Symptoms

  • A change in bowel habits that lasts for more than a few days. This includes diarrhea, constipation, or a sensation that your bowel is still not empty after a bowel movement.
  • Vomiting
  • Unexplained weight loss
  • Stools that are thinner than usual.
  • Stools that appear slimy or that have a mucous film on them
  • Yellow skin, also called jaundice
  • Persistent gas pains, bloating, fullness, or cramps
  • Constant tiredness, dizzy episodes or increasing paleness of your face and hands
  • Bright red or very dark blood in your stool. This can be a symptom of several things besides cancer. If you have this symptom, see a doctor right away.
  • Lower abdominal pain


Diagnostic procedures for colorectal cancer may include the following:

  • Digital rectal examination (DRE): A health care provider inserts a gloved finger into the rectum to feel for anything unusual. This test can detect cancers of the rectum but not the colon.

  • Fecal occult blood test: This test checks for hidden blood in the stool.

  • Sigmoidoscopy: A short, flexible, lighted tube, called a sigmoidoscope, is inserted into the intestine through the rectum.

  • Colonoscopy: This test involves inserting a colonoscope, a long, flexible, lighted tube, through the rectum up into the colon. The doctor can see the lining of the colon, remove tissue for examination, and possibly treat some problems that are discovered.

  • Barium enema: A fluid called barium is inserted in the rectum to partially fill up the colon. An X-ray of the abdomen shows narrowed areas, blockages, and other problems.

  • Biopsy: Tissue samples are removed for examination to determine if cancer or other abnormal cells are present.

  • Blood count: This test checks for anemia, a result of bleeding from a tumor.

Prevention and Treatment

When colorectal cancer is diagnosed, testing determines how much cancer is present and if it has spread to other parts of the body. This is called staging and is an important step toward planning a treatment program, which may include surgery, radiation therapy, or chemotherapy.

It's possible to prevent many colorectal cancers through screening. Finding these cancers early is the best way to improve the chance of successful treatment. Your doctor can explain which screening option is right for you.

Medical Reviewer: [Alteri, Rick MD, Foster, Sara M. RN, MPH] Last Annual Review Date: 2009-07-15T00:00:00-06:00 Copyright: 2000-2010 The StayWell Company, 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

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