Delivering low-amplitude, high-frequency ultrasound waves could fragment a kidney stone more quickly than existing high-amplitude, low-frequency treatments
Kidney stones are crystals that form when waste products in the blood collect in the kidneys. Some people pass these without any discomfort, however stones can cause considerable abdominal pain if they get stuck in the kidneys or the ureter, the small tube that connects the kidneys to the bladder.
Relatively small kidney stones are often treated via shock wave lithotripsy (SWL), which involves delivering high-amplitude, low-frequency ultrasound waves to a stone for up to an hour, usually while the person is under sedation. This fragments the stone so it can be more easily passed in the urine. Larger stones may require surgery.
Jonathan Harper at the University of Washington in Seattle and his colleagues have developed a less painful treatment that also uses ultrasound waves, but at a lower amplitude and higher frequency, dubbed burst wave lithotripsy (BWL).
In its first human study, 19 people with 25 kidney stones between them underwent BWL for up to 10 minutes. About 90 per cent of the stones’ volume fragmented, from up to 12 millimetres to less than 2 millimetres. In SWL, about 60 per cent of stones are generally fragmented to less than 4 millimetres. A 4-millimetre fragment can usually be excreted, but more painfully than with smaller stones.
“Burst wave lithotripsy has the potential to be administered in awake patients without anaesthesia,” says Harper.
“We’ll start a study any day now in the clinic where people come in with stones, we break them and then we try to push them out so that they are really clear of the kidney when the person leaves,” he says.
Journal reference: The Journal of Urology, DOI: 10.1097/JU.0000000000002446
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