The bowel is part of the digestive system, which is sometimes called the gastrointestinal (GI) or digestive tract. The digestive system starts at the mouth and ends at the anus. It helps the body to break down food and turn it into energy. It also gets rid of th parts of food that the body doesn't use. This solid waste matter is called stools or faeces.
There are two main parts of the bowel:
The large bowel has several sections.
|Caecum||A pouch at the beginning of the large bowel that receives waste from the small bowel. The appendix is a small tube hanging off the end of the caecum.|
|Colon||The main working area of the large bowel. The colon is divided into four parts (ascending colon, transverse colon, descending colon and sigmoid colon) and stretches from the caecum to the rectum. It is about 1.5m long.|
|Rectum||The last 15cm to 20cm of the large bowel.|
|Anus||The opening at the end of the digestive tract. The anus has strong muscles that keep it closed. During a bowel motion, these muscles relax to release stools from the rectum.|
Bowel cancer is cancer in any part of the large bowel (colon or rectum). It's sometimes also known as colorectal cancer.
Bowel cancer grows from the inner lining of the bowel (mucosa). It may develop from growths on the bowel wall called polyps. Polyps are usually harmless (benign), but they may become cancerous (malignant) over time. Malignant polyps may be small or large, flat or mushroom-shaped.
If untreated, bowel cancer can grow locally into the deeper layers of the bowel wall. It can spread from there to the lymph nodes (glands). These small, bean-shaped masses are part of the body's lymphatic system. If the cancer advances further, it can spread to other organs, such as the liver or lungs (metastasis).
In most cases, it develops fairly slowly and stays in the bowel for months or years before spreading.
Bowel cancer is the second most common cancer affecting people in Australia. About 14,000 people are diagnosed with bowel cancer every year. About one in 17 men and one in 25 women will develop bowel cancer before the age of 75. It's most common in people over 50, but it can occur at any age.
In its early stages, bowel cancer often has no symptoms. However, some people may experience the following:
Not everyone who has these symptoms has bowel cancer. Other medical conditions, such as haemorrhoids or tears in anal tissue, and some foods or medications, can also cause these changes. If you have any of the above symptoms for more than two weeks, see your doctor for a check-up.
"I started to have some bleeding when I went to the toilet. There were no other warning signs – it just happened out of the blue, so I went to see my GP."
The exact cause of bowel cancer isn't known. However, some factors increase the chance of developing it:
Polyps in the bowel are a risk factor for bowel cancer. If polyps are removed, the risk of bowel cancer is reduced but it can still occur.
There are two rare conditions running in families that cause a small number (5% to 6%) of bowel cancers:
If one or more of your family members (such as a parent, sibling or grandparent) have been diagnosed with bowel cancer, it may run in your family. This is a possibility if two relatives on the same side of your family have cancer, or if they were diagnosed before the age of 55.
Other cancers, such as breast cancer, can also run in the family, and this may increase your risk of developing bowel cancer. If you're concerned about your family history, see your general practitioner (GP) for regular check-ups and discuss whether you should have a further assessment.
Doing regular physical activity, maintaining a healthy weight and eating a diet high in fruit, vegetables and fibre may help protect against bowel cancer.