INTRODUCTION

Electrohydraulic lithotripsy (EHL) is primarily used in the endoscopic fragmentation of difficult bile [1-15] and pancreatic duct stones [5,16,17]. It was originally used in the Soviet Union as an industrial tool for fragmentation of rocks. It was first used to treat bile duct stones in 1975 when it was performed through a T-tube tract using fluoroscopic guidance.

An advantage of EHL compared with other methods for treating difficult stones is that it is portable, rapid, efficient, and relatively inexpensive. EHL is typically used during peroral or percutaneous choledochoscopy or peroral pancreatoscopy. Because these techniques are not widely available, EHL is mostly used in tertiary centers with expertise in the endoscopic management of biliary tract disorders. (See "Cholangioscopy and pancreatoscopy".)

EHL has also been used for treatment of urinary tract stones, a setting where it has largely been replaced by other methods to achieve stone fragmentation (particularly Holmium laser lithotripsy). Laser lithotripsy for bile duct stones has not been widely adopted in part because of the costs and limited availability of equipment [18], but Holmium laser lithotripsy has been used successfully at various endoscopy centers, including ours, for the management of biliary and pancreatic stones [19]. (See "Laser lithotripsy for the treatment of gallstones".)

This topic review will focus on the technical aspects and efficacy of EHL in the management of bile duct and pancreatic duct stones. Other methods for treating bile and pancreatic duct stones, including laser lithotripsy, extracorporeal shock wave lithotripsy, and standard mechanical lithotripsy, are discussed separately. (See "Laser lithotripsy for the treatment of gallstones" and "Extracorporeal shock wave lithotripsy for pancreatic stones" and "Endoscopic management of bile duct stones: Standard techniques and mechanical lithotripsy".)

THEORETICAL BACKGROUND

The principle of EHL is the creation of an electric high-voltage spark between two isolated electrodes located at the tip of a fiber. The electric sparks are delivered in short pulses that create an immediate expansion of the surrounding liquid, inducing a spherical shock wave. The shock wave oscillates, generating sufficient pressure to fragment the stone. In vitro studies using chalk to simulate a stone and a 3.3 Fr probe have demonstrated that short pulses of high peak pressure provided by a low capacity and a high voltage have a greater impact on fragmentation than the corresponding broader shock waves of lower peak pressure carrying the same energy [20]. Application of EHL is best achieved under direct visualization, since shock waves can also injure normal tissue.