Bowel cancer

Wednesday 24 March, 2010

Reviewed by: Assoc. Prof. Michael Jefford MBBS, MPH, MHlthsevMt, PhD, MRACMA, FRACP, Consultant Medical Oncologist, Peter Mac; Dr Suzanne Kosmider, MBBS, FRACP, Medical Oncologist, Western Hospital.

 On this page: The bowel | Bowel cancer | Causes of bowel cancer | How common is bowel cancer?

The bowel

The bowel is the longest part of the digestive system (the ‘gut'). The digestive system is the long tube that runs from the back of the mouth, forms the stomach and bowel, then ends at the rectum and anus. It winds around inside the body. Food passes through it and is digested and absorbed. The waste products are passed out as bowel motions.

The bowel is made up of two sections. The small bowel is where food is absorbed. This leads into the large bowel, where only water and salts are absorbed. The large bowel has two parts: the colon, which is about one and a half metres long, and the rectum, which is about 15 centimetres long. The rectum leads to the outside of the body through the anus.

Diagram of the digestive tract including the bowel

Bowel cancer

Bowel cancer generally affects the colon or rectum. Cancer of the small bowel is rare. Bowel cancer starts in the lining of the bowel (the mucosa). If untreated it spreads deeper into the wall of the bowel. From there, it can spread to lymph nodes in the area. Later, bowel cancer can spread to other areas including the liver or lungs.

Sometimes bowel cancer starts in polyps, that grow in the lining of the bowel. Polyps look like small mushrooms. These polyps are quite common in people over the age of 50 and are usually benign. However, some polyps can grow and become cancerous. People with familial adenomatous polyposis (FAP) have a lot of polyps in their bowel. They are at much greater risk of bowel cancer.

Causes of bowel cancer

The causes of bowel cancer are not clearly understood. Some risk factors make it more likely that a person will develop bowel cancer. These include:

How common is bowel cancer?

Bowel cancer is the most common cancer that affects men and women in Victoria. More than 3500 people are diagnosed each year. Bowel cancer mainly affects people over the age of 50 but can occur at any age.

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