Suction-enabled access sheaths nearly 6x the odds of clearing kidney stones—but 87% heterogeneity makes that number nearly meaningless
Journal: Medicina (Kaunas, Lithuania) | Published: 2026-03-13 | Type: Systematic Review, Meta-Analysis | PMID: 41901617 Authors: Cho Seok, Lee Joo Yong, Jung Hae Do, Park Min Gu (Inje University Ilsan Paik Hospital; Severance Hospital/Yonsei University; Korea University — all South Korea) Funding/COI: Funding not reported. Authors declare no conflicts of interest.
Flexible and navigable suction ureteral access sheaths (FANS-UAS) are a newer tool used during flexible ureteroscopy for kidney stones; they add continuous suction to the standard sheath, theoretically improving visibility and stone fragment clearance. This meta-analysis of 9 comparative studies (1,791 patients) found FANS-UAS associated with substantially higher stone-free rates and fewer complications than conventional sheaths. The headline OR of 5.99 should be read with extreme caution: the studies pooled to produce it have an I² of 86.7%, meaning the individual study results vary so wildly that a single pooled estimate is of limited interpretive value.
Of the 9 included studies, only 2 are randomized controlled trials. Of those two RCTs, one (Zhu et al.) was rated low risk of bias; the other (Cacciatore et al.) had unclear allocation concealment, no blinding, and was rated SIGN 1−. The remaining 7 studies were non-randomized: one prospective, six retrospective. Four of those were rated SIGN 2+ (well-conducted cohort studies with propensity matching or multicenter design); three were rated SIGN 2− due to retrospective single-center designs and uncontrolled confounding. The authors followed PRISMA and used appropriate statistical models (fixed-effects for low heterogeneity outcomes, random-effects where I² exceeded 50%). The meta-analytic framework is methodologically sound.
The fatal problem is the SFR heterogeneity. An I² of 86.7% signals that these studies are not measuring the same thing under the same conditions — differences in patient selection, stone composition, laser systems, operator experience, and outcome definitions at various institutions all bleed into that pooled OR. The point estimate of 5.99 cannot be taken at face value.
The complication data here is worth taking seriously — consistent across all 9 studies, zero heterogeneity, and a large effect size (OR 0.33). The stone-free rate finding is not: an I² of 86.7% means the studies were too different from each other to pool meaningfully, and the resulting OR of 5.99 is a number in search of a context. This paper is a well-executed meta-analysis of a methodologically weak evidence base. It is useful as a structured map of what's been done and where the gaps are; it is not useful as definitive evidence that FANS-UAS is superior for stone clearance. The conclusion that "current evidence supports the growing adoption of FANS-UAS" oversells what the data actually shows.