Abstract
To investigate the flow field characteristics and optimize negative-pressure stone removal strategies using computational fluid dynamics (CFD). A three-dimensional CFD model integrating the UAS, flexible ureteroscope, urinary tract, and spherical stone fragments (1–3 mm) was developed. The low-Reynolds-number *k-ε* turbulence model was applied to simulate the steady, incompressible flow under varying negative pressures. Stone size, position, and sheath parameters significantly affected removal efficiency. 1 mm stones achieved a peak suction force of 0.54 N at 5 mm from the scope tip; 2 mm stones reached 1.68 N at 45 mm, with proximal 1–2 mm fragments experiencing repulsion. 3 mm stones generated the highest force (6.6 N) at 15 mm but showed “jumping” instability due to turbulence. Vortex shedding and low-pressure zones downstream of stones enhanced mobility. The 12/14Fr sheath balanced clearance efficiency and safety. This study revealed that stone size, distance from the scope tip and UAS geometry synergistically regulate clearance efficiency. The identification of a "high-efficiency clearance region" (5–15 mm) and optimal 12/14Fr UAS configuration provides actionable insights for clinical practice, while the proposed optimization framework offers a theoretical basis for next-generation UAS design and standardized negative-pressure stone retrieval protocols.
Data availability
The CFD simulation data used to support the findings of this study are available from the corresponding author upon reasonable request.
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Funding
This project was supported by Peking University People’s Hospital research and development funds (RDL 2024–21), Tongzhou District Science and Technology Program Project (WS2025081), and Beijing Health Technologies Promotion Program (BHTPP2022082).
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Authors and Affiliations
Contributions
Data curation: Cong Tian, Jun Liu. Formal analysis: Bo Yang, Liulin Xiong. Funding acquisition: Jun Liu. Investigation: Qi Di. Methodology: Cong Tian, Jun Liu. Project administration: Cong Tian, Jun Liu. Resources: Baigali Zhang Software: Cong Tian, Jun Liu. Supervision: Cong Tian, Jun Liu. Validation: Cong Tian, Jun Liu. Visualization: Cong Tian, Jun Liu. Writing – original draft: Cong Tian. Writing – review and editing: Jun Liu.
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Competing interests
Cong Tian and Jun Liu declare that they contributed equally to this work. Remaining all authors declare no conflict of interest.
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Glossary
- Flexible Ureteroscopy Lithotripsy (fURS)
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A minimally invasive surgical approach for treating upper urinary calculi, involving the use of a flexible ureteroscope to access and break down kidney or ureteral stones.
- Ureteral Access Sheath (UAS)
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A hollow, tube-like medical device inserted into the ureter to facilitate the passage of a ureteroscope, maintain access, and enable irrigation or suction during urological procedures.
- Computational Fluid Dynamics (CFD)
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An engineering methodology that uses numerical analysis and algorithms to simulate and analyze the behavior of fluid flows, applied here to model flow fields in UAS-assisted stone removal.
- Stone-Free Rate (SFR)
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A key clinical outcome measure indicating the proportion of patients who have no residual stone fragments (or fragments smaller than a specified size) after stone removal procedures.
- Negative-Pressure Suction-Assisted Stone Retrieval
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A technique integrating negative pressure with UAS and irrigation to enhance the removal of stone fragments, reduce migration, and control renal pelvic pressure.
- Low-Reynolds-Number k-ε Turbulence Model
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A computational model used to simulate turbulent fluid flows with low Reynolds numbers (laminar-dominated flows), accounting for viscous effects and boundary layer characteristics.
- Reynolds-Averaged Navier–Stokes (RANS) Equations
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A set of equations used in CFD to model turbulent flows by averaging the Navier–Stokes equations over time, enabling the prediction of mean flow behavior.
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Tian, C., Liu, J., Di, Q. et al. Computational fluid dynamics-based flow field simulation and optimization of negative-pressure stone removal: stone size, position, and sheath geometry. Sci Rep (2026). https://doi.org/10.1038/s41598-026-41399-1
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DOI: https://doi.org/10.1038/s41598-026-41399-1
