Kidney Stones

Background

Clinical KeyOne in 20 people will develop a kidney stone, and the symptoms include flank pain, which may be severe and blood in the urine. Stones 4 mm and smaller are likely to pass on their own, and those greater than 9 mm are more likely to need intervention prior to passage. Staying hydrated can help prevent kidney stones and once you have had a kidney stone, you are more likely to have another one. They are most common in the 50-70 age group.

Current Treatment

There are several methods of treatment, starting with hydration and pain relief and progressing to more invasive methods. Alpha blockers and calcium channel blockers can relax the spasm of the ureter and allow the stone to pass down to the bladder. For larger stones, Extracorporeal Shock wave lithotripsy (ESWL) can be used to break up the stone in your body, and then fragments will pass. For stones in the kidney, a percutaneous nephrolithotomy can use small scopes to penetrate to the kidney to help remove the stones. Some stones can be reached with a small scope that passes through your bladder and ureter to reach a smaller stone or fragment to remove it. A tube can also be places which allows the stones to pass down to the bladder to exit. Many of these procedures require general or regional anesthesia and limiting factor for many of them relates to the location of the stone. If the stone is not in a suitable location, a more invasive approach must be taken.

Focused Ultrasound

The ability to move stones in the genitourinary track can be very helpful in some patients. For patients with multiple stones or for those who have had ESWL, there is a potential for the fragments to locate in the lower pole. Treatment success is based on both stone fragmentation and clearance of the fragments. The tendency of accumulation in the lower pole can have longer term implications, as the fragments can grow in size resulting in the need for another removal procedure. Additional uses include treatment of asymptomatic calculi in pilots, pregnancy or in those with a solitary kidney. One can also reposition a stone for better access by ESWL, ureteroscopy or percutaneous nephrolithotomy.

The mechanism of moving the stones is based on the application of focused ultrasound to a location that is adjacent to the stone. As the energy is applied, there is an acoustic wave that spreads. When the wave hits the stone, the energy is transmitted to the stone, resulting in an acoustic radiation force. This force is transmitted to the stone, and acts along the propagation axis of the acoustic wave. The movement is based on the initial location of the wave and the position of the stone. Alterations in the location of the wave can enable directional control of the stone.

Clinical Trials

The ability to use focused ultrasound to move stones or stone fragments has been demonstrated in adult patients. The team used focused ultrasound to reposition stone fragments ranging from 5mm-10mm in 14 out of 15 patients. Of the 43 total targets, 28 (65%) showed some level of movement, while 13 (30%) were moved 3mm or more to a new location. Stone direction was controlled and 4 out of the 6 patients who had ESWL eliminated 30 fragments. The largest stone moved was 10mm, and one patient had temporary discomfort when a 10mm stone was moved at the ureteropelvic junction. There were no adverse events with the treatment.

There are currently no additional studies on using focused ultrasound to move kidney stones. While the initial work is positive, it remains to be seen if there will be further research and/or approval steps that will be pursued.

Notable Papers

Harper JD, Cunitz BW, Dunmire B, Lee FC, Sorensen MD, Hsi RS, Thiel J, Wessells H, Lingeman JE, Bailey MR. First in Human Clinical Trial of Ultrasonic Propulsion of Kidney Stones. J Urol. 2016 Apr;195(4P1):956-64. doi: 10.1016/j.juro.2015.10.131.

Ikeda T, Yoshizawa S, Koizumi N, Mitsuishi M, Matsumoto Y. Focused Ultrasound and Lithotripsy. Adv Exp Med Biol. 2016;880:113-29. doi: 10.1007/978-3-319-22536-4_7. Review.

Pfau A, Eckardt KU, Knauf F. [Diagnosis and treatment of nephrolithiasis. What is established?]. Internist (Berl). 2015 Dec;56(12):1361-8. doi: 10.1007/s00108-015-3758-0. Review. German.

Oweis GF, Dunmire BL, Cunitz BW, Bailey MR. Non-invasive measurement of the temperature rise in tissue surrounding a kidney stone subjected to ultrasonic propulsion. Conf Proc IEEE Eng Med Biol Soc. 2015;2015:2576-9. doi: 10.1109/EMBC.2015.7318918.

Abrol N, Kekre NS. Focused ultrasound guided relocation of kidney stones. Indian J Urol. 2015 Jan-Mar;31(1):28-32. doi: 10.4103/0970-1591.139577.

Harper JD, Dunmire B, Wang YN, Simon JC, Liggitt D, Paun M, Cunitz BW, Starr F, Bailey MR, Penniston KL, Lee FC, Hsi RS, Sorensen MD. Preclinical safety and effectiveness studies of ultrasonic propulsion of kidney stones. Urology. 2014 Aug;84(2):484-9. doi: 10.1016/j.urology.2014.04.041.

Wang YN, Simon JC, Cunitz BW, Starr FL, Paun M, Liggitt DH, Evan AP, McAteer JA, Liu Z, Dunmire B, Bailey MR. Focused ultrasound to displace renal calculi: threshold for tissue injury. J Ther Ultrasound. 2014 Mar 31;2:5. doi: 10.1186/2050-5736-2-5.

Connors BA, Evan AP, Blomgren PM, Hsi RS, Harper JD, Sorensen MD, Wang YN, Simon JC, Paun M, Starr F, Cunitz BW, Bailey MR, Lingeman JE. Comparison of tissue injury from focused ultrasonic propulsion of kidney stones versus extracorporeal shock wave lithotripsy. J Urol. 2014 Jan;191(1):235-41. doi: 10.1016/j.juro.2013.07.087.

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. Focused ultrasound to expel calculi from the kidney: safety and efficacy of a clinical prototype device. J Urol. 2013 Sep;190(3):1090-5. doi: 10.1016/j.juro.2013.03.120.

Khokhlova T, Li T, Sapozhnikov O, Hwang JH. The use of twinkling artifact of Doppler imaging to monitor cavitation in tissue during high intensity focused ultrasound therapy. Proc Meet Acoust. 2013 Jun;19(1). pii: 075034.

Duryea AP, Maxwell AD, Roberts WW, Xu Z, Hall TL, Cain CA. In vitro comminution of model renal calculi using histotripsy. IEEE Trans Ultrason Ferroelectr Freq Control. 2011 May;58(5):971-80. doi: 10.1109/TUFFC.2011.1898.

Alan C, Koçoğlu H, Ateş F, Ersay AR. Ultrasound-guided X-ray free percutaneous nephrolithotomy for treatment of simple stones in the flank position. Urol Res. 2011 Jun;39(3):205-12. doi: 10.1007/s00240-010-0336-8.

Shah A, Owen NR, Lu W, Cunitz BW, Kaczkowski PJ, Harper JD, Bailey MR, Crum LA. Novel ultrasound method to reposition kidney stones. Urol Res. 2010 Dec;38(6):491-5. doi: 10.1007/s00240-010-0319-9.

     

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