May PC et al, 2016: Ultrasonic propulsion of kidney stones.
May PC, Bailey MR, Harper JD.
Department of Urology, University of Washington School of Medicine bCenter for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, Washington, USA.
Abstract
PURPOSE OF REVIEW: Ultrasonic propulsion is a novel technique that uses short bursts of focused ultrasonic pulses to reposition stones transcutaneously within the renal collecting system and ureter. The purpose of this review is to discuss the initial testing of effectiveness and safety, directions for refinement of technique and technology, and opinions on clinical application.
RECENT FINDINGS: Preclinical studies with a range of probes, interfaces, and outputs have demonstrated feasibility and consistent safety of ultrasonic propulsion with room for increased outputs and refinement toward specific applications. Ultrasonic propulsion was used painlessly and without adverse events to reposition stones in 14 of 15 human study participants without restrictions on patient size, stone size, or stone location. The initial feasibility study showed applicability in a range of clinically relevant situations, including facilitating passage of residual fragments following ureteroscopy or shock wave lithotripsy, moving a large stone at the ureteropelvic junction with relief of pain, and differentiating large stones from a collection of small fragments.
SUMMARY: Ultrasonic propulsion shows promise as an office-based system for transcutaneously repositioning kidney stones. Potential applications include facilitating expulsion of residual fragments following ureteroscopy or shock wave lithotripsy, repositioning stones prior to treatment, and repositioning obstructing ureteropelvic junction stones into the kidney to alleviate acute renal colic.
Curr Opin Urol. 2016 Feb 3. [Epub ahead of print]
Comments 1
One of the strongest arguments against SWL and in favour of endourological treatment modalities is the common occurrence of residual fragments following disintegration of stones in the kidney. Although residual fragments also are seen after endourological removal of stones (Figure) it is the higher risk of residuals following SWL that has remained in focus of the debate.
A non-invasive method to improve fragment movement and elimination is therefore highly desirable. Accordingly several reports have given support to the usefulness of inversion + vibration treatment.
The present report is highly interesting inasmuch as stones and fragments could be moved within the kidney by means of ultrasound propulsion. The method that was clinically tested in 15 patients, after a series of experimental studies, showed that it was possible to re-position stones and fragments successfully and painlessly in 14.
The technique is under development with the primary aim to construct an ultrasound probe with a larger focus than that used in the described studies.
The results presented in this report are indeed highly interesting and it is tempting to speculate that combination of ultrasound propulsion with inversion therapy might be a superb solution for patients left with residual fragments after non-invasive or low-invasive stone treatment. It might also be an excellent device before or even during SWL.