Objective:To explore the clinical features and risk factors of systemic inflammatory responses syndrome (SIRS) after flexible ureteroscopic lithotripsy (FURL) with upper urinary tract stones.Methods:A retrospective of 157 patients with upper urinary calculi treated by FURL who were admitted to Suzhou First People′s Hospital from January 2018 to October 2020 were selected to analyze the treatment results and complications of the patients. Patients were divided into SIRS group ( n=31) and non-SIRS group ( n=126) according to whether they were complicated by SIRS. The clinical data between the two groups were analyzed by a single factor, and the factors with statistical significance were included in the LASSO-Logistic regression analysis. Visualize the model through the Nomogram, and verify and evaluate the discrimination and accuracy of the model. Results:The results of univariate analysis showed that gender( P=0.010), average stone size ( P<0.05), preoperative urine white blood cell count ( P<0.05), operation time ( P<0.05) and postoperative stone bacterial culture ( P<0.05) were different between the two groups and the differences were statistically significant. The LASSO-Logistic regression analysis results show that the above factors were all independent risk factors for patients with SIRS. The Nomogram complicated SIRS risk prediction model constructed based on the above risk factors has good discrimination and high consistency with actual observations. Conclusion:Females, large stones, high preoperative white blood cell counts, longer operation time, and positive bacterial culture of postoperative stones are independent risk factors for SIRS after FURL in patients with upper urinary calculi.