Cancer Types

Bowel Cancer

Information about bowel cancer.

What is the bowel?

The bowel is part of the food digestive system. It joins the stomach to the rectum and helps waste material (faeces or poo) to leave the body. The bowel is made up of the small bowel (small intestine) and large bowel (large intestine). The large bowel consists of the colon and rectum.

What is bowel cancer?

Bowel cancer develops when abnormal cells in the colon or rectum grow in an uncontrolled way. The cells can form small growths called polyps, which can turn into cancer over time. Polyps are common and most do not develop into cancer. Also, not all bowel cancers develop from polyps. Bowel cancer can also be called colon, rectal or colorectal cancer depending on where the cancer starts.

Who can be affected by bowel cancer?

Bowel cancer affects men and women and is most often found in people who are 50 years and older. The chance of getting bowel cancer increases with age and in people with a family history of bowel cancer.

Risk factors

Anything that can increase your risk is called a risk factor. Having one or more of these risk factors does not mean that you will develop bowel cancer. Some of these risk factors can't be changed (e.g. age) while others can (e.g. diet).

The risk factors for bowel cancer are:

  • Being over 50 years old
  • Having a close family member diagnosed with bowel cancer before 55 years old
  • Having two or more close family members of the same side of your family who have had bowel cancer
  • Having a known genetic bowel cancer syndrome in your family (such as familial adenomatous polyposis (FAP), Lynch Syndrome or other rare conditions)
  • If you have previously had polyps (adenomas) in the bowel and close family members who have had polyps in the bowel
  • Having inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease.

Other risk factors that may increase the risk of bowel cancer:

  • Being overweight or obese
  • Tobacco smoking
  • A low-fibre, high-fat diet
  • A diet high in processed and red meat
  • Drinking alcohol

Signs and symptoms

There may be no warning signs that you have bowel cancer. Some signs and symptoms of bowel cancer may include:

  • Bleeding from your bottom or blood in your faeces (poo)
  • A change in your regular bowel habit that continues for several weeks (especially loose or more frequent poo)
  • Abdominal pain, cramping or bloating
  • Unexplained weight loss
  • Unexplained tiredness or fatigue

Although these symptoms are usually caused by conditions other than cancer, it's important to get them checked by your doctor as soon as possible.

Finding bowel cancer early

The best thing you can do to find bowel cancer early is to get screened for bowel cancer every two years, beginning at age 60 and continuing to age 74. If the screening test finds blood in your bowel motion, follow up investigations can detect changes and early signs of cancer before it has developed or before there are any symptoms.

The bowel screening test is free, and is sent to people aged 60 to 74 years in the mail every two years.

For more information on screening in your area, visit the National Bowel Screening Programme.


Bowel cancer may be identified after a screening test shows signs that you may have cancer, or after you visit your doctor with symptoms of bowel cancer (e.g. bleeding from the bottom). Usually the first test used to look for bowel cancer is called a colonoscopy. A colonoscopy is done using a long, thin, flexible tube containing a camera and a light to examine the entire length of the large bowel.

Other tests that may also be used to diagnose bowel cancer include a biopsy of the bowel (a tiny piece of tissue is taken to examine under the microscope), a sigmoidoscopy (internal examination of the lower part of the large intestine), CT scan or MRI scan (images taken of the bowel). Sometimes bowel cancer is diagnosed as a result of surgery of the bowel.

If bowel cancer is diagnosed, some more tests may be done to find out the stage of the disease and if it has spread anywhere else in the body. These tests may include a CT scan, MRI, ultrasound, chest X-ray, and lymph node biopsy.


If you are found to have bowel cancer, you will be referred to a specialist. A team of health professionals will look after your care.

The treatment for bowel cancer depends on the type and stage (how far it has spread), the severity of the symptoms, your general health and preferences.

Polyps that may turn in to cancer can be removed during the colonoscopy (see diagnostic tests above). If cancer has not spread into the muscle of the bowel, no further treatment may be needed.

If cancer has spread beyond the bowel wall, the primary treatment is surgery to remove the tumour. The bowel walls will then be joined together. If it is not possible to join the bowel walls together, a special hole called a stoma will be made to the outside of the body. A colostomy bag will be attached to this hole to collect waste from the bowel.

In some cases, chemotherapy (medicines to destroy cancer cells) or radiotherapy (radiation to destroy cancer cells) may be recommended.

Helpful websites

Bowel Cancer New Zealand

National Bowel Screening Programme