New guidelines from the National Health & Medical Research Council (NHMRC), Australia's peak health body, recommend yearly testing for bowel cancer for all well adults from the age of 50.

Bowel cancer is a malignant tumour which starts in the wall of the large bowel (colon or rectum) and affects one in 20 Australians. The risk increases from the age of 40, rising sharply from 50 years. The danger signals for bowel cancer are blood in your bowel motions, a recent change in bowel habits or abdominal pain. You should see your doctor if you develop any of these symptoms, especially if you are over 40.

Investigations available

Most bowel cancers develop from polyps, benign tumours on the lining of the bowel. Screening tests can detect polyps and early cancer before symptoms develop, giving the best chance of cure.

Bowel cancer or polyps may be found by:

1. Tests for blood in the stools (bowel motions). This involves checking three samples, and detects 40-80% of cancers.

2. Sigmoidoscopy. This test involves passing an instrument in through the back passage and into the lower 40-60 cm of the bowel. Sedation is usually not needed.

3. Colonoscopy. An instrument is passed around the entire large bowel, after thorough emptying. Sedation is required.

Who is at increased risk?

Your risk of bowel cancer is greater if:

• One or more close relatives had bowel cancer or polyps, especially below 55 years
• You previously had bowel cancer or polyps
• You have had ulcerative colitis over 8 years.

Who should be tested?

The NHMRC guidelines recommend all well adults at average risk have annual tests for blood in the stools from the age of 50 (some experts say 40). This can be combined with sigmoidoscopy every five years.

If you are at high risk, colonoscopy every five years is recommended, starting from age 50, or 10 years before the age of first diagnosis of bowel cancer in the family. Stool tests can also be used in the years between testing. People at very high risk should be tested more often.

Speak to your doctor about your risk and what tests you may need.