CVAC 2.0 outperforms FANS sheath for larger stone fragment clearance in bench model

A bench-model comparison of 2 suction-enabled ureteroscopy platforms found that CVAC 2.0 demonstrated superior stone clearance and reduced ergonomic burden compared with a flexible and navigable suction access sheath (FANS) system for moderate-to-larger stone fragments, according to findings presented by Jared S. Winoker, MD.¹

The study used a 5-calyx silicone kidney model to evaluate aspiration efficiency across 4 fragment-size strata, ranging from approximately 20 µm to 3.3 mm, using matched 1g Bego stone loads. Each device completed 20 trials per condition, run to complete removal or 5 minutes. FANS trials used the LithoVue ureteroscope paired with an 11/13 Fr ClearPetra sheath; a single surgeon completed NASA Task Load Index (TLX), ergonomics, and satisfaction assessments for both platforms.

Performance was equivalent for small fragments. In the sub-460 µm condition, both devices achieved near-complete clearance—CVAC at 100% and FANS at 97% (P = .18). With larger fragments (median 640 µm and above), the platforms diverged substantially. CVAC achieved complete or near-complete clearance across all larger fragment strata, whereas FANS clearance fell to 74%, 73%, and 49% for progressively larger size groups (all P < .05). Relative clearance favored CVAC by 1.7×, 1.6×, and 1.9× across those strata. Residual volumes remained low for CVAC (≤36 mm³) but rose to 152–299 mm³ with FANS.

Winoker attributed the performance divergence to several mechanical factors.

"The most obvious is the physical size of that outflow space between the FANS sheath and the scope and the ability of fragments to fit there," he said. Beyond physical clearance, he pointed to the annular—rather than circular—geometry of the FANS outflow tract, the variability in that geometry along the sheath's length, and the directionality of inflow from the scope, which may push fragments away from suction rather than toward it. CVAC's outward-angling irrigation jets, by contrast, are designed to improve aspiration efficiency.

FANS also required repeated scope withdrawal and partial reinsertion to manage fragments that could not traverse the scope-sheath interface—a workflow disruption reflected in significantly higher NASA-TLX Physical and Temporal demand scores (both P = .006), greater arm and hand discomfort (P = .003), and lower overall satisfaction (P < .001). Winoker acknowledged the findings aligned with his clinical experience.

"The findings certainly corroborate some of the ergonomic and efficiency frustrations that, at least in my opinion, at times occur with FANS," he said, noting that repeated aspiration maneuvers "can lead to stone burden being left behind, which is going to affect patient outcomes." He was less concerned about mucosal trauma from scope movement, noting that withdrawals largely occur within the sheath.

Winoker was candid about the study's limitations. The bench model was designed to isolate aspiration mechanics, which was intentional—but real-world procedures are dominated by active laser lithotripsy and passive fragment accumulation rather than bulk debris removal.

"In real life, the majority of your time performing these procedures involves laser lithotripsy and passive aspiration of the accumulating fragments and dust, such that you shouldn't have to be actively aspirating out a one-gram pile of debris," he said. Additional bench testing completed since submission has validated the published findings, and he identified the logical next step as applying the model to more complete, representative procedural simulations inclusive of lithotripsy.

REFERENCE

1. Winoker J, Lee H, Jaekel D. Simulated kidney study of CVAC 2.0 vs. FANS: Fragment clearance and surgeon workload. Presented at: 41st Annual Congress of the European Association of Urology. March 13-16, 2026. London, United Kingdom. Abstract A0158