This retrospective study included patients with upper urinary calculi who underwent endoscopic lithotripsy in the urology ward of the First Affiliated Hospital of Zhejiang University between June 2018 and May 2020. SIRS was diagnosed according to the Guidelines for the diagnosis and treatment of urological diseases in China (2014 edition [12]. The inclusion criteria were 1) ≥ 18 years of age, 2) upper urinary calculi diagnosed by imaging examination (including abdominal computed tomography, plain abdominal X-ray, and kidney, ureter, and bladder X-ray), and 3) underwent unilateral or bilateral PCNL, fURS, or URS. The exclusion criteria were (1) SIRS caused by other systemic infections after the operation, (2) history of other operations within 3 months, (3) preoperative basal heart rate ≥ 90 beats/min, (4) immunocompromised patients, (5) malignant tumor, or (6) incomplete clinical data. This study was approved by the Clinical Research Ethics Review Committee of the First Affiliated Hospital, Zhejiang University School of Medicine (#2022 Expedited Review Number 203). The Clinical Research Ethics Review Committee of the First Affiliated Hospital, Zhejiang University School of Medicine, waived the requirement of informed consent because of the retrospective nature of the study.

All patients underwent urine cultures before the operations. They received preoperative antibiotics 1 day before surgery.

All patients underwent endoscopic lithotripsy (URS, fURS, or PCNL) routinely.

After anesthesia, the patient was set in the bladder lithotomy position. The ureteroscope was placed into the bladder through the urethra and under the action of perfusion water pressure, and the bladder and bilateral ureteral orifice were observed for any abnormality. The zebra guidewire was inserted into the affected ureter as a guide, the perfusion water pressure was adjusted, and the ureteroscope was slowly placed under direct vision to observe whether there were calculi and stenosis throughout the ureter. After the calculi were found, the holmium laser fiber was inserted, the calculi were crushed to less than 2 mm, the fiber was pulled out, and part of the gravel was clamped to the bladder using foreign body forceps or directly pulled out of the body, and a double J tube was indwelled.

In the same way as for conventional URS, the ureteroscope was inserted into the ureter to observe whether there were calculi and stenosis throughout the ureter. Then, the ureteroscope was withdrawn, a soft ureteroscope sheath was placed into the ureteroscope, and a soft ureteroscope was placed into the renal pelvis. The calculi in the renal pelvis were found, and the conditions in the renal calyces were observed. Indwelling double J tube guided by zebra guidewire was performed.

Under ureteroscopy, a ureteral catheter was inserted into the affected side under the guidance of a zebra guidewire, and water dripping through the catheter was used to form transient artificial hydronephrosis. The patient was turned over, and the incision area was prepared routinely. The needle was inserted into the middle calyces of the affected kidney under B-mode ultrasound guidance, the guidewire was inserted, and the needle was withdrawn through a 1-cm incision of the skin at the puncture site. The fascia dilator was expanded to the appropriate circumference (F8-F24), and the nephroscope channel was established to find the stone. A holmium laser or ultrasonic stone crusher was inserted to break the stone, which was then flushed out. A zebra guidewire was inserted in the direction of the guide wire, and a double J tube was inserted. After careful examination of the visual area confirming no residual stone, the ureteroscope was withdrawn, and a nephrostomy tube with appropriate circumference was inserted.

The patient demographic information and clinical characteristics were retrieved from the hospital’s electronic medical record system. The demographic information included age, sex, admission time, sex, height, weight, and body mass index (BMI). The clinical indicators included imaging and hematological examination results, operative methods (URS, fURS, and PCNL), diabetes history, history of other chronic diseases (cardiovascular and cerebrovascular diseases, hepatic insufficiency, and renal insufficiency), stone location (involving the ureter or limited to the kidney), stone long diameter, degree of hydronephrosis, anatomical abnormality or not, history of operation on the affected side, preoperative infection history, operative methods, operation time, percutaneous nephroscope channel, staghorn calculi or not, preoperative urine culture results, and length of hospital stay, solitary kidney or not, and simultaneous bilateral surgery or not.

Data entry was carried out independently by two researchers in Microsoft Excel;the datasets were compared, and discrepancies were verified and corrected. SPSS 19.0 (IBM, Armonk, NY, USA) was used for statistical analysis. The continuous data conforming to the normal distribution were presented as means ± standard deviation and analyzed using one-way analysis of variance (ANOVA). The categorical data were presented as n (%) and analyzed using the chi-square test. Bonferroni’s method was used for multiple comparisons. Multivariable logistic regression analysis was used to identify the independent risk factors associated with SIRS. Two-sided P-values < 0.05 were considered statistically significant.