Data collection and Follow up
All the patients’ data were obtained from the hospital’s electronic medical record system. The characteristics of the patients which include the age, gender, body mass index(BMI), stone burden, history of previous surgery on the ipsilateral side, urine cultures, whether or not using antibiotics and comorbidities. The operation time, postoperative hospital stay, one-time success rate of lithotripsy, renal function and hemoglobin changes before and after operation were recorded. In addition, the postoperative complications were also recorded according to the modified Clavien-Dindo classification as recommended. KUB examination was performed in all cases on the first day after operation. All patients were follow up routinely in the outpatient clinic at 1 to 3 month postoperatively. At 1 month postoperatively, non-contrast CT and urinary ultrasound were performed to confirm the stone clearance status, in which stone-free rate (SFR) was defined as radiological residual fragments less than 4mm, and the double J stent was removed in the outpatient clinic. If the residual stone fragments were more than 4mm, the removal of double J stent would be delayed until 3 months.