Dogs have a nose for cancer

Devoted owners have long suspected that man's best friend can do more than just wag its tail or fetch sticks.

Now, it seems dogs can be trained to detect cancer - by sniffing their owner's urine.

Scientists found that a selection of pets - a mongrel, a labrador, three cocker spaniels and a papillon - identified samples from patients with bladder cancer nearly three times more often than would be expected by chance.

The dogs even picked up a kidney tumour in a patient who was not known to have the disease and which had been missed in two scans. Asurprised consultant ran a third test and confirmed the disease.

The suggestion that dogs might be able to smell cancer was first made in 1989 by two London dermatologists. A woman asked them to cut a mole out of her leg because her dog constantly sniffed it, even through trousers. One day, the animal tried to bite the mole off when she was wearing shorts.

It turned out she had malignant melanoma - a deadly form of skin cancer - which was caught early enough to save her life. In the latest study, dogs of different ages were trained for seven months to discriminate between urine from patients with bladder cancer and those without the disease.

They correctly identified samples - by lying next to them - 41 per cent of times, rather than 14 per cent expected by chance, scientists from Amersham Hospital, Buckinghamshire, told British Medical Journal.