Evaluation of electrohydraulic lithotripsy as a means of gallstone fragmentation in a canine model

Abstract

Electrohydraulic lithotripsy (EL) is defined as the fragmentation of calculi or stones by electrically induced fluid shock waves. The objective and rationale of EL is to reduce the size of large retained stones so that stone fragments can be removed without the inherent risks and morbidity of surgical intervention. Lithotripsy equipment consists of a power source generator and a bipolar coaxial electrode. The generator discharges a rapid series of sparks across the two poles of the electrode tip. When the electrode tip is placed in a solution and discharged, these high voltage sparks cause an explosive evaporation and sudden expansion of the surrounding fluid which initiates the creation of hydraulic shock waves. When a shock wave travels through a liquid medium, its energy can be absorbed by an abrupt increase in acoustical impedance or resistance such as a stone. Absorption of shock wave energy within the stone leads to a build-up of pressure gradients and formation of tear and shear forces which eventually cause fragmentation. For more than a decade EL has been used successfully in urology for cystoscopic disintegration of vesical calculi.,2 Urolithiasis and choledocholithiasis present similar clinical problems, i.e., if a stone does not pass spontaneously, pain, ductal obstruction, or infection force surgical intervention for stone removal. Endoscopic EL for biliary calculi fragmentation is not currently performed. We report the results of our preliminary studies using an animal model to evaluate EL as a potential means of gallstone fragmentation in the common bile duct.