LONDON, Oct 31, 2004 (United Press International via COMTEX) -- British scientists have invented a "smart stethoscope" that can hear a kidney stone that has been broken down by treatment, the BBC reported Sunday.

Doctors can use the stethoscope to hear echoes created by shock wave therapy, or lithotripsy, to determine whether the therapy worked.

Tests at Guy's Hospital in London indicated that use of the stethoscope can save patients unnecessary repeat therapy and x-ray monitoring.

Lithotripsy hits kidney stones with thousands of shock waves in an effort to break them into pieces small enough to urinate out of the body or be dissolved by drugs.

But there is no way to tell how the process worked, other than x-rays before and after treatment.

Kidney specialists at Guy's Hospital and scientists at Southampton University wanted to learn whether echoes produced by shock waves could be used to determine the treatment's effectiveness.

Southampton Prof. Tom Leighton said the smart stethoscope picks up sounds and sends them to a box, which amplifies and changes the sounds' frequency so the doctor can hear them.

When the stone is intact, the doctor hears a "tick," and when it has been shattered, the sound changes to a "tock," he said.

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