A barium X-ray can reveal the site of the tumour
A type of bacterium known to cause dental decay and skin ulcers may also be linked to bowel cancer, scientists suspect.
Two independent research teams have now found the bug Fusobacterium in colon tumours.
It's not yet clear if the pathogen might cause cancerous changes or whether it is an incidental finding, they toldGenome Research journal.
If it is to blame, antibiotics might be able to treat it and prevent cancer.
Bowel cancer is the third most common cancer in the UK after after breast and lung.
Although the exact cause of bowel cancer is unknown, there are certain factors that increase risk, such as a strong family history of the disease and older age.
It may be that Fusobacterium infection can be added to that list, according to the experts, but they say much more work is needed to establish this.
The infection has already been linked with a gut condition called ulcerative colitis which is itself a risk factor for bowel cancer.
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Early warning signs and symptoms
- A persistent change in normal bowel habit, such as going to the toilet more often and diarrhoea, especially if you are also bleeding from your back passage
- Bleeding from the back passage without any reason, particularly over the age of 50
- A lump in your tummy or a lump in your back passage felt by your doctor
- Unexplained iron deficiency in men or in women after the menopause
- Unexplained extreme tiredness
And other cancers are known to be linked with certain bacteria and viruses - for example, HPV and cervical cancer.
The first study, led by Dr Robert Holt from Simon Fraser University in Canada, identified Fusobacterium's hallmark in RNA present in bowel cancer tumours. RNA is genetic material similar to DNA which is involved in transmitting and translating the genetic code.
The other team, led by Dr Matthew Meyerson from the Dana-Farber Cancer Institute in Boston, US, found microbial sequences of DNA indicative of Fusobacterium.
Together, they looked at more than 100 samples of healthy and cancerous bowel tissue.
Sarah Williams, of Cancer Research UK, said the research gave a clue about the environment in which bowel cancer grows, but added: "It's early days and we look forward to the results of more specific, in-depth studies.
"In the meantime, people can reduce their risk of bowel cancer by not smoking, cutting down on alcohol, keeping a healthy weight, being active, reducing the amount of red and processed meat in their diet and eating plenty of fibre."
