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Bowel cancer diagnosis

3 min read

Bowel cancer can develop without any early warning signs. The cancer can grow on the inside wall of the bowel as a polyp for several years before it undergoes changes to become cancerous and spreads to other parts of the body. Often very small amounts of blood leak from these growths and pass into the bowel motion before any symptoms are noticed.

Screening involves testing for bowel cancer in people who do not have any obvious symptoms of the disease. The aim is to find any polyps, or to find cancers early when they are easier to treat and cure.

A bowel cancer screening test called a faecal occult blood test (FOBT) is used to detect small amounts of blood in the bowel motion, but not for bowel cancer itself.

Screening for bowel cancer using a FOBT is a simple, non-invasive process that can be done in the privacy of your own home. Although no screening test is 100% accurate, the FOBT is currently the most well-researched screening test for bowel cancer.

Completing a FOBT every two years can reduce the risk of dying from bowel cancer by 15 to 25%. People with symptoms of bowel cancer or who have a family history of bowel cancer should consult their doctor as soon as possible.

Further tests are required to diagnose bowel cancer and your doctor will discuss this with you. They may involve:

  • Physical examination and history - an exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
  • Digital rectal examination - an exam of the rectum. The doctor or nurse inserts a lubricated, gloved finger into the rectum to feel for lumps or anything else that seems unusual.
  • Barium enema - a series of X-rays of the lower gastrointestinal tract that shows any swellings or lumps. A liquid that contains barium (a silver-white metallic compound) is put into the rectum. The barium coats the lower gastrointestinal tract and X-rays are taken. This procedure is also called a 'lower GI series'.
  • Colonoscopy or sigmoidoscopy - a procedure to look inside the rectum and colon for polyps, abnormal areas or cancer. A colonoscope is inserted through the rectum into the colon. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
  • CT or MRI scan - CT scans produce three-dimensional pictures of several organs at the same time and can be used to examine the bowel. An MRI scan produces detailed cross-sectional pictures of the body and can show the extent of any tumours.
  • PET scan - a small amount of radioactive glucose is injected into the body. When scanned, cancer cells will appear brighter.
  • Ultrasound - a test using soundwaves that echo when something dense is found, such as a tumour. This test can see if the cancer has spread.
  • Biopsy - the removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer.

Cancer Australia can provide more information on bowel cancer on their website at

Sometimes it is helpful to talk to others about your experience.  Cancer Council Australia offers support for you and your loved ones via their helpline on 13 11 20.

Last reviewed: August 2016

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