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JU INSIGHT Fragmentation of Stones by Burst Wave Lithotripsy in the First 19 Humans

By: Jonathan D. Harper, MD; James E. Lingeman, MD, FACS; Robert M. Sweet, MD; Ian S. Metzler, MD; Peter Sunaryo, MD; James C. Williams, Jr., PhD; Adam D. Maxwell, PhD; Jeff Thiel, BS; Bryan W. Cunitz, MS; Barbrina Dunmire, MS; Michael R. Bailey, PhD; Mathew D. Sorensen, MS, MD, FACS | Posted on: 01 May 2022

Harper JD, Lingeman JE, Sweet RM et al: Fragmentation of stones by burst wave lithotripsy in the first nineteen humans. J Urol 2022; https://doi.org/10.1097/JU.0000000000002446.

Study Need and Importance

There is an unmet need for an office-based ultrasound system to image, break and reposition stone fragments to facilitate their natural clearance.

What We Found

Fragmentation effectiveness of such a system was tested in 19 human subjects and 23 stones. Transcutaneous application of focused, cyclic ultrasound pulses called burst wave lithotripsy (BWL) was applied for up to 10 minutes in anesthetized subjects. A ureteroscope was inserted and video was recorded with a laser fiber for scale. Independent review of the video determined the percentage the original stone volume (mean stone size 5.7±1.7 mm) was comminuted to fragments 2 mm or less and linearly extrapolated to the time for 100% of the fragments to be ≤2 mm (see table). The video was lost for subject 9, and no stones were seen in subjects 10 and 11. Independent video review found only mild reddening and bleeding on the papilla. No other adverse events (AEs) associated with the device or procedure were identified.

Table. Fragmentation outcomes with ≤10 minutes of BWL

Subject % Fragments ≤2 mm Projected Time to All Fragments ≤2 mm (mins)
1 100 ≤10
2 73 ≤10
3 100, 20 ≤10 50:00
4 90 11:06
5 100, 100 ≤10
≤10
6 67 14:56
7 20, 8 50:00
124:20
8 100 ≤10
12 0 Not applicable
13 5 200:00
14 0 Not applicable
15 26, 1 36:00
200:00
16 100 ≤10
17 100, 98 ≤10 10:14
18 100, 100, 95 ≤10
≤10
≤10
19 85 ≤10
Median (IQR) 90
(20, 100)		 10
(10, 14.9)

Limitations

Due to operating room time constraints, BWL was limited to 10 minutes per stone and complete comminution was linear extrapolated rather than continuing to full comminution and stone clearance. A single transducer at 1 frequency (390 kHz) was used, and evidence suggests the option to use a second transducer with a higher frequency or broader beam may have improved effectiveness on stones smaller than 3 mm and larger than 10 mm, respectively. Given the feasibility study design, these cases were accompanied by ureteroscopy and as needed laser lithotripsy, so the detection of AEs due to BWL may be masked by the side effects of ureteroscopy; however, all reported AEs were mild and resolved spontaneously.

Interpretation for Patient Care

BWL combined in 1 system with ultrasound imaging and ultrasonic propulsion to expel fragments is feasible and a potential clinic-based technology to manage urinary calculi in awake unanesthetized patients.

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