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.

Background: Flexible 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.

Methods: Our 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.

Results: IO-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.

Conclusion: This 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.