Doctors may finally have a use for dog's ability to learn all kinds of things from sniffing urine. A group of doctors from the United Kingdom decided to see if they could train dogs of different breeds to detect the distinct aroma of bladder cancer.

What they wanted to know: Can dogs recognize the smell of bladder cancer in people's urine?

What they did: The researchers took urine samples from 36 men and women with bladder cancer and 108 people who were either completely healthy or had a urological disease that was not cancer. They trained six dogs (a mongrel, a Labrador, a papillon, and three cocker spaniels) to distinguish the distinct smell of urine from bladder cancer patients from both healthy people and those with other diseases. The dogs were offered seven urine samples, and they had to pick out the correct one by lying next to it.

What they found: Out of 54 total tests, the dogs picked out the correct sample 41 percent of the time. That might not seem like such a high success rate, except when you consider their odds of getting it right without any ability (by chance alone) are only 14 percent. So, the researchers concluded that the dogs can be trained to sniff out bladder cancer. One participant in the study who was part of the healthy controls was picked several times by the dogs as being the cancerous sample. When doctors went back and tested that person again they found small amounts of kidney cancer. The cocker spaniels and the papillon were better sniffers than the lab or the mongrel, but they had an unfair advantage because those four dogs were given liquid samples, while the lab's and the mongrel's samples were dried overnight.

What it means to you: These dogs were professionally trained, so don't think your little Muffin is going to be your cancer detection tool. But if researchers can train dogs to reliably detect cancer, it could be an effective, and cuddly, screening technique sometime in the future.

Caveats: The author of an editorial praising the study declared a conflicting interest: He owns a chocolate Labrador.

Find out more: Several scientists in Florida are training their dogs to sniff out certain cancers. Their website has pictures and a fairly science-heavy explanation of their training.

Descriptions of the anatomy of a dog, including its sense of smell, can be found on the website of a professor at Davidson College.

Read the article: Willis, C.M. et al. "Olfactory Detection of Human Bladder Cancer by Dogs: Proof of Principle Study." British Medical Journal. Sept. 24, 2004, Vol. 329, No. 7468, pp. 712–714.

Accompanying editorial: Cole, T.J. "Teaching Dogs New Tricks." British Medical Journal. Sept. 24, 2004, Vol. 329, No. 7468, p. 715.

Full text online: http://bmj.bmjjournals.com