Login to Access Video or Poster Abstract: MP19-13
Sources of Funding: Work supported by NIH NIDDK grants DK043881 and DK104854, the National Space Biomedical research Institute through NASA NCC 9-58, and resources from the VA Puget Sound Health Care System.

Introduction

Burst Wave Lithotripsy (BWL) is a developing alternative to shockwave lithotripsy for non-invasive nephrolithiasis treatment. Ultrasonic propulsion (UP) utilizes ultrasound pulses to push stones or fragments within the collecting system. Using low intensity pulses, UP may augment the effects of BWL by ejecting fragments off the primary stone, reorienting the stone to allow BWL exposure at different angles, and displacing surrounding dust fragments that shield the stone. Therefore, we hypothesized that BWL combined with concurrent UP pulses would improve stone breakage compared to BWL alone.

Methods

Two types of artificial stones (1.calcite and 2.Begostone) and human calcium oxalate monohydrate (COM) stones, measuring 5-8 mm, were individually tested in a polyvinyl chloride tissue phantom. The phantom with stone was placed in a water bath and aligned with a 335 kHz BWL transducer and 2.5 MHz ultrasonic propulsion-capable imaging probe. Each stone was exposed to 5-10 min of treatment (5 min for calcite, 10 min for Begostone or COM). We performed trials applying BWL alone, BWL followed by UP, and BWL with interleaved UP. UP rate was varied from 1-60 pulses/min, while BWL settings remained constant. Stone breakage success was defined by the percentage of stone broken into fragments smaller than 2 mm.

Results

Stone breakage success for calcite stones was 63% greater when treated with BWL and UP at 3 pulses/min (BWL alone 24±19%, BWL with UP 39±24%). Begostones treated with a similar protocol had 4.5-fold greater stone breakage success (BWL 6±4% and BWL with 6 pulses/min UP 27±8%), but was only 1.8-fold greater when UP was performed for 10 minutes after the BWL session (BWL followed by 6 pulses/min UP 11±2% breakage). Begostones treated with BWL and UP had greater breakage when propulsion pulses were applied at a faster rate, with stone breakage of 6±1%, 22±3%, and 35±5% at 0(no propulsion), 6, and 60 pulses/min, respectively. COM stones treated with the same protocol of increasing pulses/min broke at 17±11%, 25±26% (p=0.13), and 36±28% (p=0.01), respectively. UP alone did not cause fragmentation.

Conclusions

BWL performed with UP improves lithotripsy in an artificial kidney model with both human and artificial stone types, compared to BWL alone. This improvement is most effective when pushes are interleaved with BWL treatment, rather than performed separately, and when more propulsion pushes are applied.

Funding

Work supported by NIH NIDDK grants DK043881 and DK104854, the National Space Biomedical research Institute through NASA NCC 9-58, and resources from the VA Puget Sound Health Care System.