First in Human Clinical Trial of Ultrasonic Propulsion of Kidney Stones

Abstract

Purpose: Ultrasonic propulsion is a new technology using focused ultrasound energy applied transcutaneously to reposition kidney stones. We report what are to our knowledge the findings from the first human investigational trial of ultrasonic propulsion toward the applications of expelling small stones and dislodging large obstructing stones.

Materials and methods: Subjects underwent ultrasonic propulsion while awake without sedation in clinic, or during ureteroscopy while anesthetized. Ultrasound and a pain questionnaire were completed before, during and after propulsion. The primary outcome was to reposition stones in the collecting system. Secondary outcomes included safety, controllable movement of stones and movement of stones less than 5 mm and 5 mm or greater. Adverse events were assessed weekly for 3 weeks.

Results: Kidney stones were repositioned in 14 of 15 subjects. Of the 43 targets 28 (65%) showed some level of movement while 13 (30%) were displaced greater than 3 mm to a new location. Discomfort during the procedure was rare, mild, brief and self-limited. Stones were moved in a controlled direction with more than 30 fragments passed by 4 of the 6 subjects who had previously undergone a lithotripsy procedure. The largest stone moved was 10 mm. One patient experienced pain relief during treatment of a large stone at the ureteropelvic junction. In 4 subjects a seemingly large stone was determined to be a cluster of small passable stones after they were moved.

Conclusions: Ultrasonic propulsion was able to successfully reposition stones and facilitate the passage of fragments in humans. No adverse events were associated with the investigational procedure.

Keywords: kidney calculi; lithotripsy; nephrolithiasis; therapies, investigational; ultrasonography.

Figure 1

Study design for ultrasonic propulsion clinical trial. Group 1 = postlithotripsy fragments; Group 2 = de novo < 5 mm stones, Group 3 = de novo > 5 mm treated before surgery, and Group 4 = de novo stones treated during ureteroscopy. Grade 1 = no movement; Grade 2 = movement < 3 mm; Grade 3 = movement > 3 mm or to new location.

Figure 2

Push motion results for subjects with postlithotripsy fragments. The number next to each target indicates the subject number. Different sized circles represent stone target sizes. Green represents stone movement and the green arrow highlights subjects that reported passing stones. The hash mark corresponds to a target that was identified as a single large stone on imaging but determined to be a cluster of small stones with ultrasonic propulsion.

Figure 3

Push motion results for subjects with small and large de novo stones. The number next to each target indicates the subject number. Different sized circles represent stone target sizes. Green represents stone movement. The purple stone highlights a subject that experienced a decrease in pain with movement of a renal pelvis stone. Only stones < 5 mm were monitored for passage (subjects #1-3), of which there were none reported. Gray indicates stones treated with the investigational device that were reported as submucosal based on ureteroscopy.

Figure 4

Stones passed by subject #4 (Group 1). (a) Shows the 2 stones that the subject passed in clinic immediately after the investigational procedure. (b) Shows an additional 14 stone fragments passed over the next couple days after the investigational procedure.

Figure 5

Ultrasound images of the potential diagnostic role of ultrasonic propulsion. (a) A single large stone or possibly 2 medium-sized stones. Arrow indicates the direction of the Push. (b) Pushing of the stone revealed 6 or more small stone fragments.