Doctors could soon be storing essential medical information under the skin of their patients, the American Medical Association says.

Devices the size of a grain of rice that are implanted with a needle could give emergency room doctors quick access to the records of chronically ill patients, America's largest doctors group said in a report.

The association adopted a policy on Monday stating that the devices can improve the "safety and efficiency of patient care" by helping to identify patients and enabling secure access to clinical information.

These radio frequency identification tags (RFIDs) are already used by Wal-Mart and other businesses to speed up their shipping systems by sending out small signals that can be scanned more easily than bar codes.

Implanting them in people "can improve the continuity and coordination of care with resulting reductions in adverse drug events and other medical errors," said the report prepared by the association's ethics committee. But the devices "also may pose some physical risks, compromise patient privacy, or present other social hazards."

The main concern is protecting the privacy of the information stored on the devices. There are also health concerns.

While the devices are removable and designed to stay in place, their small size could allow them to move to other parts of a person's body.