No need to undergo unpleasant examinations to spot an early symptom of bowel cancer – one of the deadliest. Now, scientists claim to have developed a new test which can detect the disease from outside one's body.

Bowel cancer or colorectal cancer includes cancerous growths in the colon, rectum and appendix. With 655,000 deaths worldwide per year, it's the third most common form of cancer. Currently the common test to detect the disease is colonoscopy either under a local or general anaesthetic.

But, the new test -- a virtual colonoscopy, or CT colonography as it is properly known -- uses a computerized tomography to produce a 3D image of the bowel from outside the body, the 'Daily Mail' reported.

According to the scientists, the only discomfort for patients of the virtual colonoscopy is that the colon needs to be inflated and so several litres -- the average is four – of carbon dioxide are pumped through a pipe inserted in rectum.

The whole process takes about five minutes, although patients need to fast for 48 hours before hand and also take a powerful laxative. The result is out in five days.

However, the CT colonoscopy is only available at John Radcliffe in Oxford and St Mark's Hospital in North-West London as of now. But, its use is expected to spread as a study on its efficiency is published later this year.

In fact, that study, led by Prof Steve Halligan, a clinical radiologist at University College Hospital London, is likely to say that not only is it safer and more comfortable than the existing way, it is also equally effective, the British newspaper report said.