Treatment Options
Electrohydraulic Lithotripsy (EHL)

Electrohydraulic lithotripsy (EHL) was the first form of contact lithotripsy developed. EHL can fragment urinary calculi of all compositions but it has the narrowest margin of safety. Injuries to structures surrounding a stone occur when the probe discharges too close to the tissues.

Electrohydraulic lithotripsy, the first technique used for intracorporeal stone fragmentation, utilizes a probe containing two electrodes separated by an area of insulation. While electric current is passed between two electrodes, a spark is created which vaporizes the water or other surrounding fluids at the end of the probe. This spark gap creates a cavitation bubble, which rapidly expands, creating a shock wave. Once the cavitation bubble collapses a secondary pressure wave is created which is then transmitted to the adjacent stone. At the stone-water interface, the difference in acoustic impedance causes energy to be released, resulting in stone fragmentation. This process is exactly similar to shock wave lithotripsy in generating a spark gap, however, the difference in EHL is that the shock wave is not focused, so the stone must be placed where the shock wave is generated (the "F1" point).

Advantages of EHL

1. Widely available
2. Inexpensive

Disadvantages of EHL

1. When utilized next to the ureteral wall it will likely perforate the ureteral wall. The risk for perforation is proportional to the size of the cavitation bubble. The perforation rate is 17.6% in one series.
2. Probe deterioration with possible shedding pieces of insulation, and possible break off of probe requiring retrieval of the device.
3. This device is not reusable. Multiple probes may be required during a single operation increasing the cost of the procedure.
4. EHL may be ineffective against some stones.

Suggested readings
Grocela JA, Dretler SP. Intracorporeal lithotripsy: Instrumentation and development. Urol Clin North Am 1997, 24:1:13-23.

Zhong P, Tong HL, Cocks FH, et al: Transient oscillation of cavitation bubbles near stone surface during electrohydraulic lithotripsy. J Endourol 1997; 11(1): 55-61.

Vorreuter R, Corleis R, Klotz T, et al: Impact of shock wave pattern and cavitation bubble size on tissue damage during ureteroscopic electrohydraulic lithotripsy. J Urol 1995; 153 (3 pt 1): 849-853.

Hofbauer J, Hobarth K, Marberger M: Electrohydraulic versus pneumatic disintegration in the treatment of ureteral stones: A randomized, prospective trial. J Urol 1995; 153 (3 pt 1): 623-625.

Elashry OM, DiMaglio RB, Nakada SY, et al: Intracorporeal electrohydraulic lithotripsy of ureteral and renal calculi using small caliber (1.9F) electrohydraulic lithotripsy probes. J Urol 1996; 156(5): 1581-1585.

Basar J, Ohta N, Kageyama S, et al: Treatment of ureteral and renal stones by electrohydraulic lithotripsy. International Urology and Nephrology 1997; 29(3): 275-280.

Teichman JM, Rao RD, Rogenes VJ, et al: Ureteroscopic management of ureteral calculi: Electrohydraulic versus holmium: YAG lithotripsy. J Urol 1997; 158(4): 1357-1361.