The one-phase therapy for calculous pyonephrosis through percutaneous nephrolithotomy (PCNL) is currently vigorously debated.After a definite preoperative diagnosis of pyonephrosis,the traditional approach1 has been initial drainage through puncture and nephrostomy.Upon the stabilization of symptoms,a second-phase operation is performed.If pus is discovered during an intra-operative puncture,a nephrostomy tube is deposited until a second elective operation.With the advancements of science and technology,the third generation EMS LithoClast master is capable of not only efficiently crushing and removing the stones,but also lowering the intra-pelvic pressure through vacuum suction.Thus the surgical risks have been greatly reduced so that many one-phase operations for calculous pyonephrosis may be completed.2 Ever since the application of EMS LithoClast master at our department since 2006,a total of 128 patients with calculous pyonephrosis have been surgically cured within one single phase.No overt complication was observed.In conjunction with the study results of high-pressure perfusion in animal models of pyonephrosis,a report was compiled as below.