First in Human Clinical Trial of Ultrasonic Propulsion of Kidney Stones

There has been a dramatic increase in the incidence and prevalence of urolithiasis within the last two decades. As of 2014, 7% of females and 10% males in the United States have kidney or ureteral stones. There are multiple treatment options including ureteroscopy (URS), percutaneous nephrolithotomy (PCNL) or Shock Wace lithotripsy (SWL). Despite technological advancements these treatment modalities often leave residual stones after the procedure. It is debated that residual stones less than 2mm are more likely to pass. However, there is a likelihood of some residual stone fragments to grow and cause health issues in the future. Authors from University of Washington developed a new ultrasonic propulsion technology to move the stone percutaneously without any intervention. This technology has been tested in vitro setting as well as in animal studies1. This report is the first study reporting the clinical use of ultrasonic propulsion to reposition kidney stones for passage using ultrasound transcutaneously. Ultrasonic propulsion can help allow small stones to pass and reposition large stones to relieve pain or obstruction. 

This was a single center prospective study. The products used were VDAS Verasonics and a HDI C5-2 Curvilinear array. The ultrasound is activated by touching the stone on the screen. Authors used two power settings, 50V and 90V depending on the depth and size of the stones targeted. The subjects were split into 4 groups. Group 1- lithotripsy within the past year, stones <5mm fragments. Group 2 consisted of subjects with small stones. Group 3 - Subjects with large stone fragments (>5mm) who will undergo URS the day after. Group 4 consisted of subjects with large stones that will undergo simultaneous ultrasonic propulsion and URS. A 10-point pain questionnaire was given to the patients before and after each procedure.

Study included a total of 15 subjects, 13 underwent the propulsion procedure without sedation and 2 with sedation because they underwent simultaneous URS. 43 stone targets were found: 24 lower pole, 10 interpolar, 5 upper pole, and 9 in renal pelvis. 28 stones showed some motion, 13 were displaced more than 3mm to a new location. The smaller stones moved more than 3mm and the larger stones only slightly moved. 4 out of 6 post PCNL passed more than 30 stone fragments. Group 2 did not pass stones, and groups 3 and four did not have stone clearance. Some previously diagnosed as single stones turned out to be clusters of smaller stones. The patients did not experience any sensation with the 50V power level, but felt a warming sensation at 90V. Rarely a few experienced a brief internal sensation. There were no adverse events. 

Authors concluded that this technology is feasible, safe and effective to successfully reposition stones and facilitate the passage of fragments in humans. This technology has a significant potential in the management of small or residual stones. It helps reduce unplanned visits or decreasing pain and increasing comfort. No sedation and there were no adverse events. If one is looking to move a stone obstructing or causing pain, they may be able to do so. 

Written By: Jonathan Harper, Bryan Cunitz, Barbrina Dunmire, Franklin Lee, Matthew Sorensen, Ryan Hsi, Jeff Thiel, Hunter Wessells, James Lingerman, and Michael Bailey
Department of Urology at University of Washington


Harper JD, Dunmire B, Wang YN, et al. Preclinical safety and effectiveness studies of ultrasonic propulsion of kidney stones. Urology 2014;84:484-9.