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Colon Cancer

Colon Cancer Overview

The human colon, or large intestine, is a muscular, tube-shaped organ measuring about 4 feet long. It extends from the end of your small bowel to your anus. Typically the first or right portion of the colon which is called the ascending colon moves up from the lower right portion of the abdomen. The next portion, or transverse colon, moves across from the right to the left side of the upper abdomen. Next, the 3rd region or descending colon moves down the left side of your abdomen. Then an S shaped or sigmoid colon portion connects the rest of the colon to the rectum which ends at the anus. The colon has 3 main functions:

  • To digest and absorb nutrients from food
  • To concentrate fecal material by absorbing fluid (and dissolved salts, also called electrolytes) from it
  • To store and control evacuation of fecal material

The right side of your colon plays a major role in absorbing water and electrolytes, while the left side is responsible for storage and evacuation of stool.

Cancer is the transformation of normal cells. The transformed cells grow and multiply abnormally.

  • Left untreated, these cancers grow and eventually spread through the colon wall to involve the adjacent lymph nodes and organs. Ultimately, they spread to distant organs such as the liver, lungs, brain, and bones.
  • Cancers are dangerous because of their unbridled growth and potential for spread. They overwhelm healthy cells, tissues, and organs by taking their oxygen, nutrients, and space.
  • Most colon cancers are adenocarcinomas-tumors that develop from the glands lining the colon's inner wall.
  • These cancers, or malignant tumors, are sometimes referred to as colorectal cancer, reflecting the fact that the rectum, the end portion of the colon, can also be affected. Anatomic differences in the rectum as compared to the rest of the colon require that these areas be separately recognized.

In the United States, 1 in 17 people will develop colorectal cancer.

  • According to reports from the National Cancer Institute, colorectal cancer is the third most common cancer in US men.
  • Colorectal cancer is the second most common cancer in US women of Hispanic, American Indian/Alaska Native, or Asian/Pacific Islander ancestry, and the third most common cancer in white and African American women.
  • The overall incidence of colorectal cancer increased until 1985 and then began decreasing at an average rate of 1.6% per year.
  • Deaths from colorectal cancer rank third after lung and prostate cancer for men and third after lung and breast cancer for women.
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Patient Comments & Reviews

The eMedicineHealth doctors ask about Colon Cancer:

Colon Cancer - Signs and Symptoms

What signs and symptoms did you experience with your colon cancer?

Colon Cancer - Diagnosis

How was the diagnosis of your colon cancer established?

Find out about genetic testing for people with a family history of colon cancer.

Colon Cancer and Genetic Testing

Author: Jay W. Marks, MD

There has been much excitement during the past decade because of the identification of defective genes (mutations) associated with colon cancer in families where colon cancer is common. When a defective gene can be identified, it is possible to examine other members of the family to see if they also carry the defective gene. Those individuals who carry the defective gene are at a very high risk (75%-100%) for developing colon cancer. The reason for the excitement is that if an individual is found to have the defective gene, his or her colon can be removed before the cancer occurs.

Only 5% of all colon cancers occur in families with a history of colon cancer and identifiable genetic defects...

Read What Your Physician is Reading on Medscape

Colon Cancer, Adenocarcinoma »

Colorectal cancer is the third most common cancer in both men and women in the United States.

Read More on Medscape Reference »

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