Bowel Cancer

Bowel cancer (also known as colorectal cancer) is the commonest type of cancer in Australian men and women after skin cancers. About 1 in 18 men and 1 in 26 women will develop bowel cancer by the age of 75.

Development of Bowel Cancer

Bowel cancer develops from the lining of the bowel (known as the mucosa) Usually bowel cancer starts off as a benign polyp. Over time (years), the polyp gets bigger and can become cancerous due to mutations within the cells.

Risk Factors for Developing Bowel Cancer

The main risk factors would be age, past history of bowel cancer and family history. The older one gets, the greater the risk especially after 50 years of age. Someone with a previous bowel cancer has a risk of developing another bowel cancer as well on other parts of the bowel. Having a close family member with bowel cancer would increase one’s risk by approximately two-fold. There are also hereditary forms of bowel cancer.

Other risk factors include a Western diet which is high in fat and low in fibre. Low calcium intake, smoking and obesity are also associated with the risks of developing bowel cancer. In addition, long-standing inflammation of the bowel such as in ulcerative colitis can lead to the development of bowel cancer.

Symptoms of Bowel Cancer

Often one does not notice any symptom until it is quite advanced hence the importance of screening programs to reduce the risks of dying from bowel cancer.

The symptoms of bowel cancer are not necessarily specific and may also be caused by other diseases affecting the bowel. Hence bowel cancer can present in many ways including:

  1. A change in bowel habits eg constipation or diarrhoea or alternating constipation and diarrhoea
  2. Passing blood eg blood mixed with one’s stools
  3. Abdominal pain
  4. Bowel blockage – eg abdominal distension, constipation, not being able to pass flatus, vomiting and abdominal pain
  5. Feeling of not being able to empty one’s bowel’s completely
  6. Feeling of tiredness, lack of energy – this could be because of anaemia from blood loss that is not noticed.
  7. Passing mucus in one’s stools

It is important that you see a doctor if you have any of the above symptoms


  1. Colonoscopy – this is the best way to look for polyps within the lining of the bowel and also to remove the polyps (usually be snaring the mushroom-shaped polyps and burning off the neck of the polyp)
  2. Barium enema – this involves the air and barium contrast being pumped up the back passage and turning around in various positions on the X-ray table to enable pictures of the bowel to be taken
  3. CT colonoscopy – this involves significant exposure to radiation
  4. Full blood examination – may show anaemia from blood loss


Very early bowel cancer may be treated adequately from colonoscopy and excision of the cancerous polyp. Most patients unfortunately end up requiring surgery as the cancer is advanced by the time it is detected.

Occasionally chemotherapy and radiotherapy is necessary depending on how advanced the cancer is and its location.