Background information about the Large Bowel

What is the large bowel?

The large bowel is a part of the digestive system and is made up of the caecum, ascending colon, transverse colon, descending colon, sigmoid colon and the rectum. It is a 1.6m long tube-like organ that is connected to the small bowel (small intestine) at one end and the anus at the other.

Its main function is to absorb water, electrolytes and nutrients from digested food that has come from the small intestine. It is also responsible for the excretion of waste material to be expelled out of the body.

Image of the Large bowel: Courtesy of The Cancer Council WA

The right side of the bowel refers to the caecum, ascending colon and transverse colon. The left side of the bowel refers to the descending colon, sigmoid colon and the rectum.

What is Bowel Cancer?

Bowel Cancer occurs when the cells that line the bowel begin to grow out of control. Bowel cancer usually develops from an existing growth on the inner lining of the colon. These growths are called polyps. Many people develop polyps, of which the majority are not cancerous, but benign or non-malignant.

The large bowel has two sections, (1) the colon and (2) the rectum, so bowel cancer is sometimes called colon cancer, rectal cancer or even colorectal cancer.

Cancers also occur in the small bowel, however most cancers occur in the large bowel. That is why bowel cancer usually refers to cancer of the large bowel.

Who is at risk of developing bowel cancer?

All people are at risk of getting bowel cancer and it becomes more common with increasing age.

Approximately 15% of people have known factors which put them at an increased risk of developing this cancer.

These factors include:

• Polyps in the colon
• Long standing inflammatory bowel disease
• Immediate family members who have been diagnosed with Familial Adenomatous Polyposis (FAP) or Hereditary Non-Polyposis Colon Cancer (HNPCC)
• A previous history of colorectal cancer

Apart from people who are at a higher risk, it is not known why one person and not another develops bowel cancer.

This study therefore aims to determine the factors that increase a person's risk of developing bowel cancer.

For your interest...

One of our study investigators, Assoc Prof Barry Iacopetta, has published a journal paper from which the WABOHS study aim originated from. To read the article, please click on the link below.

Iacopetta, B. (2002). "Are there two sides to colorectal cancer?" International Journal of Cancer 101(5): 403-8.

WABOHS thanks and acknowledges The Cancer Council WA for providing the information on bowel cancer. For more information about Colorectal Cancer, The Cancer Council WA Colorectal Cancer brochure (pdf format, 92.4kb) is available.