Bowel cancer symptoms and risk factors

What are the symptoms?

Some people have no symptoms and the cancer is found through screening. However, many people with bowel cancer experience some of the symptoms listed below.

Talk to your doctor if you have any of these symptoms, especially if they are ongoing, get worse, or if there is any bleeding:

• blood in or on faeces (poo) or on the toilet paper; this might be bright red or make the poo look dark brown or black
• a persistent or unexplained change in bowel habits, such as diarrhoea or loose stools, constipation or smaller, more frequent bowel movements
• a change in the look of faeces (e.g. narrower or with mucus)
• a feeling of fullness or bloating in the abdomen (belly) or a strange sensation in the rectum, often during a bowel movement
• a feeling that the bowel hasn’t emptied completely after you have done a poo
• losing weight without trying to
• rectal or anal pain
• a lump in the rectum or anus
• abdominal pain or swelling
• weakness or fatigue, dizziness or breathlessness
• a low red blood cell count (anaemia or iron deficiency)
• a blockage in the bowel.

Other conditions can also cause the same symptoms, including:

• irritable bowel syndrome (IBS)
• diverticulitis (inflammation of pouches in the bowel)
• inflammatory bowel disease
• haemorrhoids, or an anal fissure (cracks in the skin lining the anus). Having some of the symptoms on this list does not mean that you definitely have bowel cancer.

What are the risk factors?

Anything that can increase your risk of cancer is called a risk factor.

For bowel cancer, these include:

• older age – bowel cancer is more common in people over 50, but the number of younger people being diagnosed is increasing
• polyps – most polyps can become bowel cancer; having a large number of polyps in the bowel is a strong risk factor
• dietary factors – a diet that is low in fibre, fruit, vegetables and wholegrains, and high in red and processed meats such as salami, ham and bacon
• smoking – increases your risk of bowel cancer and bowel polyps
• drinking alcohol – the less alcohol you drink, the lower your risk. If you choose to drink, follow the Australian Alcohol Guidelines
• body weight – being above a healthy weight
• physical inactivity – not moving your body enough. Be active on most days and minimise long periods of sitting
• strong family history – a small number of bowel cancers and types of polyps run in families
• other bowel diseases – inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis, significantly increase risk, particularly if you have had the disease for more than 10 years (IBS does not increase your risk)
• other cancers – people who have had bowel cancer are more likely to develop a second bowel cancer; some people who have had ovarian cancer or cancer of the  uterus, or who have had radiation treatment to the abdomen/pelvis, may also have an increased risk of bowel cancer
• type 2 diabetes – this may increase your risk of bowel cancer
• rare genetic disorders – some bowel cancers are linked to an inherited gene or condition (e.g. cystic fibrosis).

Can bowel cancer run in families?

Sometimes bowel cancer runs in families. The risk of developing bowel cancer may be higher if one or more of your close family members (a parent, brother or sister) has had bowel cancer. The risk is higher if they were diagnosed before the age of 50, or if 2 or more close relatives have had bowel cancer. A family history of some other cancers, such as cancer of the uterus (endometrial cancer), may also increase the risk (see Cancer Council Victoria's information on Lynch syndrome).

Some people have an inherited faulty gene that increases their risk of developing bowel cancer. These faulty genes are responsible for a small number of bowel cancers in the population.

There are 2 main genetic conditions that occur in some families:

Lynch syndrome – Less than 5% of bowel cancers are linked to Lynch syndrome, which causes a fault in the gene that helps repair a cell’s DNA. People with Lynch syndrome have an increased risk of developing bowel cancer, cancer of the uterus, and other cancers such as kidney, bladder and ovarian. Bowel cancer may also happen at a younger age than usual.

Familial adenomatous polyposis (FAP) – This condition is linked to about 1% of bowel cancers. It causes hundreds of polyps to form in the bowel. If these polyps are not removed, they may become cancerous. If you have a family history, talk to your doctor about regular check-ups or ask for a referral to a family cancer clinic.

To find out more, call Cancer Connect on 13 11 20.