Harper JD et al, 2013: Focused ultrasound to expel calculi from the kidney: safety and efficacy of a clinical prototype device
Harper JD, Sorensen MD, Cunitz BW, Wang YN, Simon JC, Starr F, Paun M, Dunmire B, Liggitt HD, Evan AP, McAteer JA, Hsi RS, Bailey MR
Department of Urology, School of Medicine, University of Washington, Seattle, Washington 98195, USA
PURPOSE: Focused ultrasound has the potential to expel small stones or residual stone fragments from the kidney, or move obstructing stones to a nonobstructing location. We evaluated the efficacy and safety of ultrasonic propulsion in a live porcine model.
MATERIALS AND METHODS: Calcium oxalate monohydrate kidney stones and laboratory model stones (2 to 8 mm) were ureteroscopically implanted in the renal pelvicalyceal system of 12 kidneys in a total of 8 domestic swine. Transcutaneous ultrasonic propulsion was performed using an HDI C5-2 imaging transducer (ATL/Philips, Bothell, Washington) and the Verasonics® diagnostic ultrasound platform. Successful stone relocation was defined as stone movement from the calyx to the renal pelvis, ureteropelvic junction or proximal ureter. Efficacy and procedure time was determined. Three blinded experts evaluated histological injury to the kidney in the control, sham treatment and treatment arms.
RESULTS: All 26 stones were observed to move during treatment and 17 (65%) were relocated successfully to the renal pelvis (3), ureteropelvic junction (2) or ureter (12). Average ± SD successful procedure time was 14 ± 8 minutes and a mean of 23 ± 16 ultrasound bursts, each about 1 second in duration, were required. There was no evidence of gross or histological injury to the renal parenchyma in kidneys exposed to 20 bursts (1 second in duration at 33-second intervals) at the same output (2,400 W/cm(2)) used to push stones.
CONCLUSIONS: Noninvasive transcutaneous ultrasonic propulsion is a safe, effective and time efficient means to relocate calyceal stones to the renal pelvis, ureteropelvic junction or ureter. This technology holds promise as a useful adjunct to surgical management for renal calculi.
J Urol. 2013 Sep;190(3):1090-5. doi: 10.1016/j.juro.2013.03.120. Epub 2013 Apr 9
PMID:23583535[PubMed - in process]. FREE ARTICLE
In this animal experiment the authors used ultrasound to move and expel stones from the lower and middle calyces of pig kidneys. From a clinical point of view such an approach is highly interesting. Stone fragments residing in the lower calyx are commonly found after SWL, not only when the stones are primarily located there, but also as a final outcome of stones disintegrated in other parts of the collecting system. It is also the common presence of residual fragments that has driven enthusiastic endoscopists to an increased use of invasive rather than non-invasive procedures. Also in numerous comparisons between SWL and RIRS or PNL, the non-invasive treatment is considered less efficient because of the presence of gravel in the kidney.
Inversion therapy with percussion has been a method applied in attempts to clear the lower calyx system and maintain the non-invasive character of modern stone removal. The results of that method are, however, as also stated in the article, variable. One explanation for that might be difficulties to know exactly where the stone fragments are located and where the percussion/vibration device should be applied.
A highly interesting approach would be to combine the described ultrasound propulsive treatment with inversion of the patient. It is thus with great interest that I look forward to further clinical experience with this method. Every kind of development that enables non-invasive rather than invasive treatment will be highly beneficial for the patient as well as for the health economy.