Extracorporeal shock wave lithotripsy induced stimulation of the obturator nerve

Extracorporeal shock wave lithotripsy to a left lower third ureteral calculus, 1.4 x 0.9 cm. large, using an unmodified Dornier HM3* lithotriptor with the patient in the sitting position produced thigh adductor movement with each shock. The procedure was terminated. Extracorporeal shock wave lithotripsy was performed uneventfully 1 week later using a Medstone STS lithotriptor with the patient in the supine position. We believe that the sitting position caused increased intra-abdominal pressure in the pelvis resulting in apposition of the ureteral segment containing the calculus to the obturator nerve, which was included either in the second focal point or in the extended shock path of the Dornier HM3 unit.