Safety and Effectiveness of the Ultrasonic Propulsion of Kidney Stones

This study tests moving kidney stones using focused ultrasound (referred to as ultrasonic propulsion). The study includes multiple population groups to investigate the ability of our technology to: a) move stone fragments to a location within the kidney to improve their chances of passage, and thus reduce the occurrence of additional symptomatic events and retreatment or b) move a symptomatic stone to relieve symptoms and pain.

Study Overview

• Status: Active, not recruiting
• Conditions: Nephrolithiasis; Urolithiasis; Kidney Stones
• Intervention / Treatment: Device: Propulse 1 with C5-2 probe; Device: Propulse 1 with SC-X probe

Detailed Description

This is an investigator initiated, NIH-funded study conducted by the University of Washington (UW). Our research group has developed a new, non-invasive technology using low intensity focused ultrasound to reposition kidney stones by imparting sufficient acoustic energy to physically move a stone. The focused ultrasound pulses are similar to pulses that may be used in elastography or acoustic radiation force imaging. Like conventional ultrasound, the probe is placed in contact with the patient's skin to image the stone following standard ultrasound imaging procedure. The same probe is then used to focus the ultrasound and apply a burst (a sequence of pulses) of acoustic force to push the stone. Brightness mode (B-mode) imaging is interleaved with the "pushing" pulses (Push-mode) to monitor stone movement. The user controls the burst amplitude. To limit heating at the probe surface, there is a slight delay before the operator can execute the next push.

In addition to undergoing the investigational procedure, the research activities include the following:

• subjects undergo a pain questionnaire before and after the procedure and report their current level of stone pain on a scale of 0 (no pain) to 10 (worst possible pain);
• the subject's skin in the area of probe placement is observed before and after the procedure;
• subjects are contacted once-a-week for 3 weeks to evaluate for potential adverse events, pain medication use, and, if applicable, stone passage;
• subjects are requested to undergo at least one follow-up imaging 4 - 12 weeks post-procedure;
• a review of each subject's medical records is conducted 90-days post-procedure to evaluate for additional effectiveness and safety events.
• Specifically for the residual fragment population (randomized control trial), subjects are contacted every 6 months for 3 years and their electronic medical record is reviewed for 5 years for stone growth, symptomatic, unscheduled medical visits, and surgery related to stones.

Subjects that qualify for the trial are recruited into different study arms (referred to as Population groups) based on their type of stone condition (de novo stone versus post-lithotripsy fragment), size of stone (≤ 5 mm or > 5 mm), and management plan (clinical observation or surgical intervention). The objectives vary based upon the Population group. Subjects may qualify for more than one population group and may undergo the investigational procedure up to 4 times total (inclusive of both the left and right-side urinary tracts). Subjects can only be enrolled in one population group at a time, there is a separate consent for each study population, and each study population is considered independent of the other groups. Recruitment into all population groups has been completed.

1. First-in-Human Population: This was the initial group of subjects included under this clinical trial. This was a 15-subject feasibility study that included a broad range of populations. This feasibility population formulated the basis for expanding the trial into a larger study addressing each population separately. This is encompassed in subject populations 2-5 below.
2. De Novo Small Stone Population: Subjects undergo the investigational procedure awake and in the clinic. To qualify the subject must have a de novo stone ≤ 5 mm in largest dimension. Ultrasonic propulsion is used with the intent to help facilitate stone passage. If the stone is larger than 5 mm, subjects could be recruited into the URS subject population (see bullet point #3 below).
3. Concurrent with URS Population: Subjects undergo the investigational procedure while anesthetized and concurrently undergoing a ureteroscopy guided laser lithotripsy procedure (referred to herein as URS). To qualify the subject must have at least one stone ≤ 20 mm in the largest dimension and be scheduled for surgery. Ultrasonic propulsion may be used to move a de novo stone or stone fragments of varying sizes generated over the course of the URS procedure. Note that since these subjects are anesthetized, a pain questionnaire is not included as part of their protocol.
4. Obstructing Stone Population: Subjects undergo the investigational procedure awake and in the clinic or emergency department (ED) setting. To qualify the subject must have clinical imaging confirmation of an obstructing stone with their pain managed and complete a urinalysis to for assess infection risk. Ultrasonic propulsion is used with the intent to relieve the obstruction and associated pain. A subset of subjects were exposed to higher amplitude dislodging pulses, in addition to the ultrasonic propulsion pulses.
5. Residual Fragment Population: Subjects undergo the investigational procedure awake and in the clinic setting. To qualify the subject must have at least one post-lithotripsy residual fragment (≤ 5 mm in largest dimension) identified either on imaging or based on the investigator's interpretation of that imaging. This is a prospective, open-label, multicenter, randomized control trial (RCT) with a treatment arm and control arm. The only difference in protocol between the two arms is that only the treatment group undergoes the investigational procedure and the associated post-procedure pain questionnaire and the post-procedure skin surface inspection. Ultrasonic propulsion is used with the intent to demonstrate: a) the ability of the ultrasonic propulsion device to reposition stones within the human kidney, b) the subsequent clinical benefit of facilitating stone passage and reducing stone burden, and c) the subsequent clinical benefit of reducing relapse. This is the only population group recruited across more than one site - the UW and the VA Puget Sound Healthcare System.

• Study Type: Interventional
• Enrollment (Actual): 172
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Washington
    • Seattle, Washington, United States, 98108
      • VA Puget Sound Health Care System
    • Seattle, Washington, United States, 98195
      • University of Washington Department of Urology

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Individuals suspected of having at least one kidney stone. This includes:

  • Patients who are being managed with watchful waiting or medical therapy
  • Patients who recently (but > 4 weeks) underwent lithotripsy treatment of their stones
  • Patients scheduled for lithotripsy treatment

Or

• Individuals suspected of having an obstructed stone. This includes:

  • Patients presenting with renal colic
  • Patients presenting with hydronephrosis or dilation of the ureter

Primary Exclusion Criteria for all groups:

• Individuals under 18 years of age
• Individuals with non-echogenic stones
• Individuals unable or unwilling to comply with the follow-up requirements
• Individuals with a coagulation abnormality or taking blood thinners or other anticoagulant at clinically significant levels
• Individuals with mobility issues who are unable to comfortably lie for up to 30 minutes or roll from their back to their side
• Individuals belonging to a vulnerable group (pregnant, mentally disabled, physically disabled, prisoner, etc.)
• Individuals who have already received four previous ultrasonic propulsion procedures.
• Individuals who have received an ultrasonic propulsion treatment within the last 4 weeks.

Additional Exclusion Criteria for Obstructing Stone population

• Individuals with a suspicion of kidney infection or exhibiting signs of sepsis
• Individuals whom the treating physician considers to be at high risk for serious alternate diagnoses such as acute infectious etiologies (e.g. cholecystitis, appendicitis), aortic aneurysm and rupture, or bowel disorders.
• Individuals who have undergone renal transplant, or individuals who will undergo dialysis.
• Individuals with bilateral hydronephrosis
• Individuals with a single kidney
• Individuals who have already received an ultrasonic propulsion investigative treatment for the same obstructing stone

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Non-Randomized
• Interventional Model: Single Group Assignment
• Masking: Single

Number of Arms

7

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: First in Human (FIH); Initial phase of the trial. Includes a broad spectrum of population groups (e.g. de novo, concurrent with URS, residual fragments) to demonstrate feasibility. Intervention consists of the non-invasive application of ultrasound to move stones within the kidney and ureter. Procedure conducted with the Propulse 1 device and C5-2 transducer. Subjects (n = 15) receive up to 40 push bursts.	Device: Propulse 1 with C5-2 probe; Move kidney stones with Propulse 1 device.
Experimental: De Novo Small Stone; Segment of the trial focused specifically on subjects with small (≤ 5 mm) stones under observation management. Intervention consists of the non-invasive application of ultrasound to move stones within the kidney and ureter with the goal to facilitate passage. Procedure is conducted with the Propulse 1 device and SC-X transducer. Subjects (n = 2) receive multiple Push bursts up to a maximum cumulative dose exposure of 5 minutes. Each burst is a maximum of 3 seconds in duration and 200 W/cm2 in intensity.	Device: Propulse 1 with SC-X probe; Move kidney stones with Propulse 1 device.
Experimental: Concurrent with URS; Segment of the trial focused specifically on subjects undergoing ultrasonic propulsion concurrently with their ureteroscopy guided laser lithotripsy procedure. Study provides visual observation of stone motion and any potential tissue injury. Intervention consists of the non-invasive application of ultrasound to move stones within the kidney and ureter. Procedure is conducted with the Propulse 1 device and SC-X transducer. Subjects (n = 18) receive multiple Push bursts up to a maximum cumulative dose exposure of 5 minutes. Each burst is a maximum of 3 seconds in duration and 200 W/cm2 in intensity.	Device: Propulse 1 with SC-X probe; Move kidney stones with Propulse 1 device.
Experimental: Obstructing Stone - Pushing only; Segment of the trial focused specifically on subjects reporting to clinic or the emergency department with an obstructing stone. Intervention consists of the non-invasive application of ultrasound to relieve pain and facilitate passage. Procedure is conducted with the Propulse 1 device and SC-X transducer. Subjects (n = 16) receive multiple Push bursts up to a maximum cumulative dose exposure of 5 minutes. Each burst is a maximum of 3 seconds in duration and 200 W/cm2 in intensity.	Device: Propulse 1 with SC-X probe; Move kidney stones with Propulse 1 device.
Experimental: Residual Fragment (Treatment group); Segment of the trial focused specifically on subjects with small (≤ 5 mm) residual fragments following lithotripsy. This is the Treatment arm of a randomized control trial. Intervention consists of the non-invasive application of ultrasound to move stones within the kidney and ureter with the goal to facilitate passage. Procedure is conducted with the Propulse 1 device and SC-X transducer. Subjects (n = 54) receive multiple Push bursts up to a maximum cumulative dose exposure of 5 minutes. Each burst is a maximum of 3 seconds in duration and 200 W/cm2 in intensity.	Device: Propulse 1 with SC-X probe; Move kidney stones with Propulse 1 device.
No Intervention: Residual Fragment (Control group); Segment of the trial focused specifically on subjects with small (≤ 5 mm) residual fragments following lithotripsy. This is the Control arm of a randomized control trial. Subjects (n = 54) follow same protocol as Residual Fragment (Treatment group) but do not receive the ultrasonic propulsion intervention.
Experimental: Obstructing Stone - Pushing + Dislodging; Segment of the trial focused specifically on subjects reporting to clinic or the emergency department with an obstructing stone. Participants were separate from the Obstructing Stone - Pushing only based on a stone skin-to-stone distance < 8 mm. Intervention consists of the non-invasive application of ultrasound to relieve pain and facilitate passage. Procedure is conducted with the Propulse 1 device and SC-X transducer. Subjects (n = 13) receive both Dislodging and Push bursts up to a maximum cumulative dose exposure of 5 minutes. This is the only population to receive the Dislodging bursts, which consist of higher amplitude (up to 7 MPa) and shorter duration pulses compared to pushing. The Push burst is a maximum of 3 seconds in duration and 200 W/cm2 in intensity.	Device: Propulse 1 with SC-X probe; Move kidney stones with Propulse 1 device.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measurement of Stone Motion Caused by Ultrasound	Percentage of study participants for which stone motion was observed on the real-time ultrasound images.	At the time of the procedure. To be evaluated with each therapy pulse over an approximately 1-hour study. Confirmed with post-procedure review of the study video.
Measurement of Stone Passage	The percentage of participants reporting visual observation of stone passage or confirmed with follow-up imaging. For the residual fragment RCT population specifically, the percentage of participants reporting visual observation of stone passage during the 3-week follow-up period after the procedure or randomization (Control group).	Measurement occurs over 3 weeks (weekly phone call or email encounter with the subject) plus review of the subject's medical chart up to the point the subject is exited from the study.
Measurement of Relapse	The percentage of participants experiencing stone relapse defined as: an unscheduled, symptomatic visit for stones on the study side, surgery for stones on the study side, or stone growth of a residual fragment measured by clinical imaging exams. This measurement is specific to the residual fragment population and associated randomized control trial. Only a single relapse event is counted per participant, though a participant could experience more than one event.	Measurement up to 5 years post-procedure. This includes a phone call or email exchange semi-annually for up to 3-years and a medical record review (including imaging) semi-annually for up to 5-years.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measurement of all adverse effects associated with the procedure	The study measures the subject-level rate of adverse events with onset after the procedure (Treatment group) or randomization (Control group) through the 3-week follow-up determined by a blinded reviewer to be potentially related to the device, procedure, or the subject's underlying kidney disease. (Secondary endpoint for both SAPs).	Measurement over 3 weeks (weekly phone call or email encounter with the subject) plus review of the subject's medical chart.

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants With Discomfort Related to the Device or Procedure	Pre-Procedure: The participant will be asked directly what discomfort, on a scale of 0 (no pain) to 10 (worst pain possible), they are experiencing and to point to where the discomfort/pain is located. This is the participant's recorded baseline measure. During Procedure: The participant will be asked directly if they are experiencing any new or different discomfort, on a scale of 0 (no pain) to 10 (worst pain possible), and to point to where the discomfort/pain is located. Any new or different discomfort above baseline will be assumed related to the device or procedure; there is no minimum threshold for reporting. Post Procedure: The participant will be asked directly what discomfort, on a scale of 0 (no pain) to 10 (worst pain possible), they are experiencing and to point to where the discomfort/pain is located. Any new or different discomfort above baseline will be assumed related to the device or procedure; there is no minimum threshold for reporting.	At the time of the procedure. To be evaluated over an approximately 1 hour study.

Collaborators and Investigators

• Sponsor: University of Washington
• Collaborators: VA Puget Sound Health Care System
• Investigators: Principal Investigator: Jonathan Harper, MD, University of Washington

Publications and helpful links

General Publications

• Dai JC, Sorensen MD, Chang HC, Samson PC, Dunmire B, Cunitz BW, Thiel J, Liu Z, Bailey MR, Harper JD. Quantitative Assessment of Effectiveness of Ultrasonic Propulsion of Kidney Stones. J Endourol. 2019 Oct;33(10):850-857. doi: 10.1089/end.2019.0340. Epub 2019 Sep 25.
• Harper JD, Cunitz BW, Dunmire B, Lee FC, Sorensen MD, Hsi RS, Thiel J, Wessells H, Lingeman JE, Bailey MR. First in Human Clinical Trial of Ultrasonic Propulsion of Kidney Stones. J Urol. 2016 Apr;195(4 Pt 1):956-64. doi: 10.1016/j.juro.2015.10.131. Epub 2015 Oct 30.
• Harper JD, Metzler I, Hall MK, Chen TT, Maxwell AD, Cunitz BW, Dunmire B, Thiel J, Williams JC, Bailey MR, Sorensen MD. First In-Human Burst Wave Lithotripsy for Kidney Stone Comminution: Initial Two Case Studies. J Endourol. 2021 Apr;35(4):506-511. doi: 10.1089/end.2020.0725. Epub 2020 Nov 5.
• Hall MK, Thiel J, Dunmire B, Samson PC, Kessler R, Sunaryo P, Sweet RM, Metzler IS, Chang HC, Gunn M, Dighe M, Anderson L, Popchoi C, Managuli R, Cunitz BW, Burke BH, Ding L, Gutierrez B, Liu Z, Sorensen MD, Wessells H, Bailey MR, Harper JD. First Series Using Ultrasonic Propulsion and Burst Wave Lithotripsy to Treat Ureteral Stones. J Urol. 2022 Nov;208(5):1075-1082. doi: 10.1097/JU.0000000000002864. Epub 2022 Nov 1.
• Sorensen MD, Dunmire B, Thiel J, Cunitz BW, Burke BH, Levchak BJ, Popchoi C, Holmes AE, Kucewicz JC, Hall MK, Dighe M, Dai JC, Cormack FC, Liu Z, Bailey MR, Porter MP, Harper JD. Randomized Controlled Trial of Ultrasonic Propulsion-Facilitated Clearance of Residual Kidney Stone Fragments vs Observation. J Urol. 2024 Dec;212(6):811-820. doi: 10.1097/JU.0000000000004186. Epub 2024 Aug 15.
• Yang CC, Keating EE, Managuli R, Honssinger N, Holt SK, Desai AC. A Randomized Controlled Trial of Ultrasonic Propulsion-Facilitated Clearance of Residual Renal Stone Fragments vs Observation. J Urol. 2025 Jul;214(1):3-9. doi: 10.1097/JU.0000000000004501. Epub 2025 Mar 3.

Helpful Links

• Link to a page at the University of Washingon Applied Physics Laboratory website that provides additional information on ultrasonic propulsion.

Study record dates

Study Major Dates

• Study Start (Actual): December 17, 2013
• Primary Completion (Actual): August 1, 2025
• Study Completion (Estimated): May 31, 2026

Study Registration Dates

• First Submitted: January 1, 2014
• First Submitted That Met QC Criteria: January 5, 2014
• First Posted (Estimated): January 7, 2014

Study Record Updates

• Last Update Posted (Actual): June 1, 2026
• Last Update Submitted That Met QC Criteria: May 29, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: lithotripsy; kidney; stones; stone fragments
• Additional Relevant MeSH Terms: Urogenital Diseases; Male Urogenital Diseases; Pathological Conditions, Anatomical; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Urinary Calculi; Pathological Conditions, Signs and Symptoms; Kidney Calculi; Nephrolithiasis; Calculi; Urolithiasis
• Other Study ID Numbers: STUDY00002746

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO