Does intraoperative surgeon reported stone free status (IO-SFS) correlate with CT based post operative stone free status (PO-SFS) in flexible ureteroscopy using flexible and navigable suction ureteral access sheath (FANS) in real-world practice? A prospective global FANS collaborative study group initiative with the section of EAU endourology.

backgroundFlexible and navigable suction ureteral access sheath (FANS) has been proven to improve stone-free rate (SFR) and many studies report high intraoperative 100% stone-free status (IO-SFS) and postoperative 100% stone-free status (PO-SFS). The reliability of IO-SFS vis-à-vis image-proven PO-SFS needs to be evaluated as it has implications on perioperative management.

methodsOur prospective, multicenter study enrolled 704 adult patients from 21 centers who underwent FURS with FANS between August 2023 and October 2024. IO-SFS was categorized into three groups: (1) 100% SFR (no dust or fragments), (2) only dust remaining, and (3) both dust and fragments remaining. PO-SFS was assessed via 2 mm non-contrast computed tomography (NCCT) at 30 days and categorized into four grades: Grade A (100% stone-free), Grade B (single ≤ 2 mm residual fragment), Grade C (single 2.1-4 mm), and Grade D (multiple or any > 4 mm). Primary outcome was correlation between intraoperative and postoperative 100% SFS. Secondary outcomes included perioperative complications, reintervention rates, and predictors of residual fragments and perioperative complications.

resultsIO-SFS reported 100% SFR in 395 cases. Postoperative NCCT confirmed a significantly higher SFS (Grade A + B) in this group (99%) compared to 95.8% in the dust only group and 61.1% in the dust and fragments group (p < 0.001). Positive predictive value (PPV) of intraoperative 100% SFR was 99% with post-op NCCT, while negative predictive value (NPV) was only 12.3%. Secondary outcome analysis showed higher stone volumes, lower pole locations, and use of high-power holmium lasers were associated with increased 2-4 mm residual fragments (OR 6.53, p = 0.047). In the 100% SFR group, the use of 12/14 Fr UAS and disposable scopes was significantly higher, with a preferred strategy combining fragmentation, dusting, and aspiration. No cases of sepsis or significant postoperative bleeding were reported due to the use of FANS, with fewer patients requiring post-operative stenting.

conclusionThis study provides robust evidence that surgeon-reported 100% IO-SFS is highly predictive of NCCT-proven postoperative stone-free outcomes, with a PPV of 99%. However, intraoperative detection of residual fragments is less reliable in predicting persistent stone burden, as only 40% of these patients eventually achieved SFS on NCCT. Standardized imaging protocols remain necessary to optimize postoperative management and patient counseling, while avoid unnecessary re-intervention.