The dog that smells colon cancer in urine samples and helps scientists create a non-invasive test

Callie is no ordinary dog. In Great Horwood, England, she spends her days sniffing jars of urine, looking for something no human eye can see.

When a cell becomes cancerous, it changes its metabolism and releases volatile organic compounds that the body expels through urination. They are chemical traces invisible to us, but not to a nose with hundreds of millions of olfactory receptors. That is where Callie comes in: trained by Medical Detection Dogs alongside the Open University, she distinguishes in blind tests the urine of patients with colorectal cancer from that of healthy people.

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Bowel cancer detection dog, Callie, identified the odour of the disease in stand 4 and made it very clear to her trainer, Mark, with a stand and stare indication and her signature tippy taps. Callie had actually missed this positive sample in a previous run, as she was working at Spaniel speed and was so excited to be in the room that she didn’t quite sniff the sample at the intensity we know is needed, so Mark put it back in a few runs later and encouraged her to slow down. There was no way she was missing it twice! #medicaldetectiondogs #dogs #fyp #thenoseknows #cancer

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When she finds a positive sample, she signals by tapping the ground with her paws. No one expects Callie to replace a doctor. Her real value lies in what she reveals: if her sense of smell can isolate the molecular pattern of the disease, scientists could use it as a map to design an early, non-invasive and accessible diagnostic test before the tumor is visible.