LONDON－A smart toilet could offer a mini health check every time you take a seat, scientists said recently, but privacy campaigners and potential users said the idea sat uncomfortably with them.

The device would identify users through an anal scan using a camera tucked under the seat before checking their waste for disease markers, including early signs of cancer, says the US-led team who developed the prototype.

"We know it seems weird, but as it turns out, your anal print is unique," said Sanjiv Gambhir, a radiology professor at Stanford University, who led work on the project.

"The smart toilet is the perfect way to harness a source of data that's typically ignored," Gambhir said. "Everyone uses the bathroom－there's really no avoiding it－and that enhances its value as a disease-detecting device."

A set of gadgets fitted inside the toilet bowl identifies the user and monitors their deposits for signs of ill health which could be shared with their doctor, researchers said in the scientific journal Nature Biomedical Engineering.

Such devices could become commonplace in homes, said Gambhir, as consumers embrace health monitoring tools like smartwatches and internet-connected home devices.

But many were concerned about flushing away their privacy, the researchers found following a 300-person survey to assess acceptance.

Three in 10 respondents said they would not want to use a smart toilet, with only about half reporting they would be "somewhat" or "very" comfortable with it.

The most commonly reported concerns were over privacy and data security, found researchers, who said information gathered would be stored in a secure, cloud-based system.

Despite those assurances, privacy campaigners expressed fears about security breaches.

"Health data contains among the most sensitive and revealing information about anyone," said Edin Omanovic, advocacy director at London-based charity Privacy International.

"Linking it to someone's biometric ID risks exposing intimate details to third parties, either through opaque data sharing or security flaws which leave back doors exposed."