'Smart stethoscope' advance in monitoring treatment of kidney stones

A new listening device, developed by scientists from the University of Southampton, is being used to monitor the effectiveness of the treatment of kidney stones - saving patients unnecessary repeat therapy and x-ray monitoring.

If kidney stones cannot be dissolved by drugs, the favoured procedure is lithotripsy. Lithotripsy works by focusing thousands of shock waves onto the kidney stones in an effort to break them into pieces small enough to urinate out of the body or be dissolved by drugs.

However, it is difficult to discover exactly when the treatment has succeeded in breaking the stone and patients frequently have to experience more shocks than necessary, or be sent home when an insufficient number of shocks have been delivered to break the stone.

The new 'Smart stethoscope' has been developed by a team from the University's Faculty of Engineering and the Environment in collaboration with Guy's and St Thomas' Foundation Trust (GSTT) and Precision Acoustics Ltd. The programme was led by Professor Tim Leighton from the University's Institute of Sound and Vibration Research (ISVR).

The 'Smart stethoscope' is placed on a patient's skin as they undergo shock wave treatment for kidney stones and assesses whether the treatment is working. It listens to the echoes, which reverberate around the body after each shock wave hits the stone. The device is now being used clinically at the London hospitals of GSTT.

Professor Leighton says: 'It's an imperfect analogy, but consider a railwayman walking along the length of a train, hitting the metal wheels with a hammer, If the wheel rings nicely, he knows that it's not cracked. If the wheel is cracked, it gives a duller sound.

'We are looking for the stone to go from being intact at the start of treatment (when it will give a nice ring 'tick' sound) to being fragmented at the end of the treatment (when it will give a duller 'tock' sound).'

Professor Leighton's research, which includes the computational fluid dynamics (CFD) use to inform judgements underpinning the invention of the smart stethoscope, is published in the latest issue of the Royal Society journal Proceedings of the Royal Society A.

Dr Fiammetta Fedele of GSTT said: 'Professor Leighton's CFD predictions of the acoustic signals emitted when bubbles collapse against kidney stones during SWL led (through collaboration with GSTT and Precision Acoustics Ltd.) to a