Shielded Electrohydraulic Lithotripsy of Urinary and Biliary Calculi: A New Possibility

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Abstract
A new transurethral lithotripsy concept, using an electrohydraulically generated shock wave to drive in a jackhammer manner a hollow spring with a metal end cap, was tested in vitro and shown to fragment urinary and biliary calculi effectively. The prototype device was fabricated from a hollow stainless steel expansion spring (1.6-mm outer diameter, 12-mm long). The primary electrohydraulic lithotripter used was the Wolf model 2137.50 (Richard Wolf Medical Instruments Corp.) with a 3.3F probe placed inside the prototype device and securely attached using a short piece of hypodermic tubing. The mechanism worked by confined electrohydraulic discharge, driving the spring and the cap to impact the stone. The results show that shielded electrohydraulic lithotripsy is effective in fragmenting both urinary and biliary calculi and is only 23% less efficient than an unshielded electrohydraulic discharge. However, the advantages to a shielded instrument may be substantial. When the shielded electrohydraulic device was discharged against the experimenter's finger, no pain was felt. Shielded electrohydraulic lithotripsy in the future may be used for ureterolithotripsy without the need for anesthesia or a ureteroscope.