WCE 2018: Quantitative Assessment of Effectiveness of Ultrasonic Propulsion of Kidney Stones

Paris, France (UroToday.com) In today’s urologic practice, surgeons are constantly trying to determine new ways of improving patient care for stones, especially with the use of new technology. At the University of Washington School of Medicine, new ultrasonic technology has recently been created which has the ability to reposition stones in the urinary tract. Dr. Patrick Samson is one such physician who helped develop the technology in Seattle and excitedly shared his center’s initial experience with the ultrasound device. The researchers attempted to determine the device’s feasibility in 13 awake and 2 anesthetized subjects. They wished to determine the safety and effectiveness of the new ultrasound transducer design, while also using ureteroscopic observation to quantify the number of kidneys in which stones were repositioned. 

In order to carry out this experimentation, the researchers would recruit patients if they were eligible and were scheduled for ureteroscopic laser lithotripsy. During the procedure, stones were repositioned using the ultrasonic device, which was recorded via ureteroscopic and ultrasound video. These videos would then be independently reviewed by 3 blinded endourologists to determine the effectiveness of the novel ultrasound transducer. Following the procedure, the safety of the patients was determined by contact each week for 3 weeks. A 90-day chart review for safety events and a clinical follow up at 12 weeks was performed to further determine patient safety. 

At the study’s completion, 15 kidneys from 14 patients were analyzed. The average BMI for the patient cohort was 28.5. The stone sizes ranged from dust to 7 mm. There was an average of 16 bursts per subject with an average total exposure of 41 seconds.  After analysis of the ureteroscopic videos by the 3 blinded endourologists, there was confirmation by all reviewers of stone movements ≥ 3 mm in 14 of 15 kidneys (93%). The remaining kidney was said to have insufficient video quality to properly determine stone movement by two reviewers. Analysis of the ultrasound videos confirmed stone movements ≥ 3 mm in 11 of 15 kidneys (73%). Of note, ultrasonic propulsion obviated the need for a basket to reposition stones in 2 cases. There were no serious adverse events observed in any patients postoperatively. However, non-serious temporary adverse events considered related to ultrasonic propulsion included skin reddening (n=3), skin bruising (n=1), and skin irritation (n=1). 

As Dr. Samson completed his presentation, he reassured the audience that the novel technology of ultrasonic propulsion was shown to be safe and effective for repositioning stones in 93% of kidneys. Though this was just the first human trial of the study, it warrants further experimentation in awake patients to further measure the clinical benefits of the device. Interestingly, Dr. Mathew Sorensen, who was in attendance, added to Dr. Samson’s presentation by stating that they are planning to move the device into production status to allow other endourologists around the world to purchase their very own. 

Figure 1: Simultaneous observation via ultrasound (A-C) and endoscopic vision (D-F) of the repositioning of a 5 mm stone in a human subject by ultrasonic propulsion from outside the body. The stone travelled approximately 1 cm in under 1 second towards and then past the scope. 

Presented by: Patrick Samson, MD, Department of Urology, University of Washington School of Medicine, Seattle, WA
Authors: Patrick Samson1, Jonathan Harper1, Jessica Dai1, Helena Chang1, Barbrina Dunmire2, Bryan Cunitz2, Jeff Thiel2, Ziyue Liu3, Michael Bailey1,2, Mathew Sorensen1,4  

Affiliation: 1Department of Urology, University of Washington School of Medicine, Seattle, WA, USA; 2Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, Seattle, WA, USA; 3Department of Biostatistics, Indiana University-Purdue University Indianapolis, Indianapolis, IN, USA; 4Division of Urology, Department of Veteran Affairs Medical Center, Seattle, WA, USA

Written by: Zachary Valley, Department of Urology, University of California-Irvine medical writer for UroToday at the 36th World Congress of Endourology (WCE) and SWL - September 20-23, 2018 Paris, France