Stones have plagued humans since ancient Egypt. One in eleven Americans has suffered from stones - more than have diabetes or cardiovascular disease. Dehydration, stasis, and bone demineralization are strong contributors to kidney stones, and occur in microgravity, increasing the risk of stones in space. Stones are often debilitating, and pilots cannot fly with stones. The total number of astronaut stone episodes has more than doubled, and a drug introduced to combat visual impairment/intracranial pressure has exacerbated the risk. Science, experience, and the negative medical consequences support concern for the risk of stones in space. NASA has focused considerable attention on stone mitigation and has made some progress. However, there are many types of stone disease, and it is unlikely that stone disease will ever be completely prevented on Earth or in space.
The goal of this study was to clinically validate the utility of a commercially viable disruptive medical technology for use during space exploration. Application to date has been on expelling stones from the kidney. This work will expand the capabilities of the technology to meet the more advanced needs in space. The investigators conducted an analog test of a new way to save astronauts from the debilitating pain of kidney stones where there currently are no treatment options. They validated, in emergency department patients, the capability to dislodge and reposition ureteral stones in two locations: the uretero-pelvic junction (UPJ) from obstructing and/or the uretero- vesical junction (UVJ). The technology will work as an adjunct to medications and other interventions used to try to prevent stone formation, ease stone passage, or mitigate pain. The capability has already been built into NASA's Flexible Ultrasound System (FUS) and as such the complexity and cost of including such a potentially game changing technology for astronaut safety is extremely low.
The experiment had the following specific aim:
- Determine the effectiveness of Ultrasonic Propulsion to reposition an obstructing ureteral stone.
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After identifying a UPJ or UVJ stone by imaging, studies were conducted at the University of Washington (UW) Medicine Emergency Departments (ED). 16 subjects were recruited for the study group and there will not be a control group. The subject were asked to fill out a pain questionnaire and rate his or her pain on a visual analogue scale (VAS). Subjects then underwent an imaging study with the investigational device by a certified sonographer with attending physician supervision. The baseline size of the stone, location of the stone, and degree of hydronephrosis were recorded. The subject was asked to again rate his or her pain to determine if it changed with the imaging exam. An ultrasound video image was recorded and raw data cine loops will be saved for select images and with each propulsion burst. The system voltage setting, patient position, and observation of stone fragmentation or movement were recorded. The stone motion was categorized as 0: no motion, 1: a small nudge or motion within a confined space, or 2: a displacement > 3 mm. The subject was asked to identify if their pain level or pain location changes using a VAS if a difference in sensation is felt. The study endpoint was when 10 minutes of ultrasound exposure had occurred, time (1 hour) is exhausted, or the physician and sonographer deemed either a successful study or that additional pushes would not improve the clinical scenario.
Participants immediately underwent a brief ultrasound exam with the investigative device to confirm the location of the stone and extent of hydronephrosis after treatment. Participants will complete a final pain questionnaire addressing any discomfort or pain they may have felt related to the procedure. The subject will be provided with a strainer to collect stones during the three-week verbal follow-up period. The subject was provided with a medical diary sheet to record their medication use during the three-week verbal follow-up period. Subjects will return after four to six weeks for clinical imaging with either low dose CT or KUB/ultrasound, similar to standard of care for urologic stenting or shock wave lithotripsy. The electronic health record (EHR) was reviewed for 90 days to assess for return visits to the ED, surgery, and/or additional imaging.
Investigators displaced obstructed stones. Detailed results will be available after the study concludes.
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Percentage of ureteral stones dislodged as a fraction of the number of stones attempted
Skin bruising at treatment site
Skin redness at treatment site
Ureteral stone movement/clearance
Ureteral stone size
Ureteral stone size location
Urinary tract infection