Inclusion Criteria:  2-4cm kidney stones. Aged 18-70 years. SMP with Ho:YAG laser or TFL.  Exclusion Criteria:  Transplanted kidney, solitary kidney, horseshoe kidney, urinary diversion, urethra deformity and other special cases. If empyema was found during SMP, the nephrostomy tube was retained and the patient was excluded from the trail.