Category: New Technology: Stones
Introduction & Objective :
The goal of our study was to evaluate preclinical safety and effectiveness of a burst wave lithotripsy (BWL) system in a porcine model.
To evaluate effectiveness of BWL treatment, a study was performed with eleven, 5-7 mm hydrated human calcium oxalate monohydrate stones surgically implanted in the kidneys and ureteropelvic junctions (UPJ) of three female farm pigs. Treatments were performed with an ultrasound transducer coupled to the skin and the focus aligned with each stone by ultrasound guidance. Exposures used an ultrasound frequency of 350 kHz, pulse duration of 20 cycles, and 10 Hz pulse repetition frequency. Peak negative focal pressures between 5 - 7 MPa were applied for 5- 30 minutes to each stone. In a separate series evaluating safety of treatment, six specific-pathogen free (SPF) pigs without stones received the exposures at 7 MPa pressure for 30 minutes to one kidney and survived for 1 week. Four SPF pigs served as untreated controls. Blood and urine were collected before treatment, after treatment and at necropsy for clinical pathology. One week post treatment, a complete necropsy was performed and histopathology was evaluated by a board certified veterinary pathologist. Studies were approved by the University of Washington Institutional Animal Care and Use Committee.
Experiments of BWL effectiveness demonstrated fragmentation in 10 of 11 stones on post mortem dissection. 8 of 11 were comminuted to fragments smaller than 4 mm. Less comminution correlated with lower pressure amplitude and shorter-duration exposures. In the safety study of BWL exposures, there were no findings of injury in any of the pigs. The clinical pathology review including hematology and urinalysis revealed all within 'normal limits' for SPF pigs.
The BWL exposures effectively fragmented kidney and UPJ stones. A separate study demonstrated that these exposures did not cause injury to the kidney or other tissues. Future work will include clinical trials to evaluate safety and efficacy in patients and research to improve BWL effectiveness in a greater variety of stones by using ultrasound image feedback and advanced exposure strategies. Work supported by NIH P01 DK043881, K01 DK104854 and R44 DK109779.
Mathew Sorensen– Associate Professor, and Urology Residency Program Director, University of Washington School of Medicine, Seattle, Washington
Yak-Nam Wang– , Seattle, Washington
Wayne Kreider– , Seattle, Washington
Jessica Dai– University of Washington, Seattle, Washington
Barbrina Dunmire– , Seattle, Washington
H. Denny Liggitt– , Seattle, Washington
Bryan Cunitz– , Seattle, Washington
Jeff Thiel– , Seattle, Washington
Michael Bailey– , Seattle, Washington
Adam Maxwell– Research Assistant Professor, University of Washington, Seattle, Washington
Oren Levy– , South San Francisco, California
Jonathan Harper– University of Washington, Seattle, Washington
Associate Professor, and Urology Residency Program Director
University of Washington School of Medicine
Research Assistant Professor
University of Washington