Predictive Value of Preoperative Urine Culture for Postoperative Fever After FANS-RIRS When Surgery Proceeds Before Culture Results Are Available

Flexible and navigable suction-assisted retrograde intrarenal surgery (FANS-RIRS) has emerged as a promising endourological technique for the management of upper urinary tract stones. By combining flexible ureteroscopy with an actively navigable suction ureteral access sheath, this technique may facilitate stone fragment evacuation, improve visualization, and potentially reduce intrarenal pressure during surgery. Despite these technical advantages, postoperative infectious complications, particularly postoperative fever, remain clinically relevant concerns after retrograde intrarenal surgery.

Preoperative urine testing is routinely performed in patients undergoing endourological stone surgery. In current clinical practice at our center, both urine routine analysis and urine culture are obtained before surgery. For patients without significant pyuria or other clinical evidence of active urinary tract infection, FANS-RIRS is usually performed without waiting for the final urine culture results. Standard perioperative antibiotic prophylaxis is administered, including one preoperative dose and one postoperative dose according to institutional practice. Under this real-world management pathway, the clinical significance of subsequently reported preoperative urine culture results remains unclear.

This prospective observational study is designed to evaluate whether preoperative urine culture results are associated with postoperative fever after FANS-RIRS. Consecutive eligible patients undergoing FANS-RIRS for upper urinary tract stones will be prospectively enrolled. Based on the final reported preoperative urine culture findings, patients will be categorized into urine culture-positive and urine culture-negative groups. Postoperative fever and other perioperative clinical outcomes will be recorded prospectively.

The primary objective of the study is to determine the association between preoperative urine culture status and the occurrence of postoperative fever in patients undergoing FANS-RIRS. The primary outcome is the incidence of postoperative fever during the early postoperative period. Secondary analyses will assess the relationship between urine culture status and other infectious outcomes, as well as explore potential clinical and perioperative risk factors for postoperative fever, including demographic characteristics, comorbidities, stone burden, laboratory findings, and operative variables.

As a prospective observational study, no intervention will be assigned by the investigators, and all diagnostic and therapeutic decisions will be made according to routine clinical practice. The findings of this study may help clarify the predictive value of preoperative urine culture in a real-world FANS-RIRS setting and provide evidence for perioperative infectious risk stratification and optimization of clinical management in patients undergoing endourological stone surgery.

Inclusion criteria

• Adult patients aged 18 years or older
• Patients diagnosed with upper urinary tract stones and scheduled to undergo FANS-RIRS
• Patients who have completed preoperative urine routine analysis and urine culture before surgery
• Patients without significant pyuria or clinical evidence of active urinary tract infection at the time of surgery, and therefore managed according to the routine institutional pathway
• Patients who are able and willing to provide informed consent

Exclusion criteria

• Age younger than 18 years
• Patients with preoperative fever or clinical evidence of active urinary tract infection requiring delayed surgery or additional treatment
• Patients with sepsis or severe infection before surgery
• Patients undergoing combined or alternative surgical procedures other than FANS-RIRS alone
• Patients with missing or unavailable preoperative urine culture results
• Patients with incomplete perioperative or postoperative clinical data
• Patients who decline to participate or withdraw informed consent