Spastic paraparesis as a complication of percutaneous nephrolithothripsy (PNL) on a calyceal calculus of the left kidney. A patient developed spastic paraparesis after surgery with ultrasound lithothripsy and litholapaxy of fragments of a renal calyceal calculus in middle-upper diverticulum. It was first assumed that the event could be due to transient spinal ischemia, caused by vasospasm of Adamkiewicz artery, secondary to blood engorgement of the area around the vessel. In order to clarify possible implications of medical liability, the Authors took into account the etio-pathogenetic mechanisms of the complication and analyzed the medico-legal aspects, with particular reference to the indication for surgery, which was not absolute in the case under scrutiny. In connection with the latter aspect, the Authors considered the conclusions of a recent sentence of the Court of Milan, whereby, despite the negative opinion of the experts specifically appointed, a case of medical liability was identified as a consequence of algodystrophy resulting from a cardiosurgical intervention. According to the Court, it is for the medical staff to demonstrate that they did all they could to prevent the complication and that such complication did not arise from a mistake on their part.