Fluid-structure interaction problems in ureteroscopy

Lead Research Organisation: University of Oxford
Department Name: Industrially Focused Maths Modelling CDT

Abstract

This student receives funding from EPSRC NPIF grant and the project falls within the EPSRC fluid mechanics and aerodynamics and continuum mechanics research areas.
This project is undertaken with Industrial Partner Boston Scientific.

Endoluminal surgery relies on high quality instrumentation combined with continuous fluid irrigation. A universal challenge is to optimise the flow of irrigation fluid through scopes to maintain good visualisation during surgery. Additionally, there is little information on how these devices affect the pressures within the kidney, with high pressures being detrimental. Finally, current systems generate a jet of unidirectional flow from the end of the scope, which, at higher pressures, forces stones away from the end of the scope. Thus a balance between sufficient flow for visualisation and limited flow to prevent retropulsion is necessary.

We will employ mathematical modelling, theoretical analysis and numerical methods, in combination with experimental studies performed in the Mathematical Institute wet lab, to advance our understanding of the fluid mechanics of ureteroscopes, and the interaction between the complex flows within the urinary tract and stone dynamics. The fluid mechanical models will be based on systematic asymptotic reductions of the Navier-Stokes equations, exploiting, e.g., the small aspect of the ureter. This will lead to reduced models that are tractable, yet physically well grounded. The flexible ureter, bladder and renal pelvis will also be modelled via the specification of appropriate constitutive laws, which will enable e.g. determination of intra-renal pressures during surgical interventions. These constitutive laws will be obtained from complementary experiments being performed in the Institute of Biomedical Engineering, University of Oxford by Professor Robin Cleveland and his team. Mathematical analysis alongside numerical investigation of these reduced models will provide significantly more physical insight into the complex urinary tract flows and their influence on stone dynamics than would be obtained by clinical studies alone.

Potential outcomes:
(i) Determination of the role of time-dependent driving pressures on flows within the upper urinary tract, which will inform new technologies for continuous fluid irrigation Initially, deformability of the urinary tract will be neglected. This will build on research during the mini-project in which flow through a scope with a working tool will be considered. Both theoretical and wet-lab approaches will be undertaken.
(ii) Building on (i), an understanding of the fluid-structure interaction problems arising from consideration of the interaction between fluid flows within the ureteroscope and urinary tract deformability. Both steady and time-dependent driving pressure gradients will be considered.
(iii) A model for the influence of the geometry of distal scope outlets on flows subject to steady and time-dependent pressure gradients.
(iv) An understanding of the role of the fluid mechanics and urinary tract deformability on the stone dynamics. Determination of the influence of scope outlets on the possibility of retropropulsion.
(v) Results from the suite of fluid-structure interaction problems will be used to inform the design of a closed-loop-control system, allowing automated adjustments to the driving pressure gradient in response to changing dynamics within the urinary tract during endoluminal surgery. Such a system will ensure flow visualisation is maintained without adverse responses (high intra-renal pressures or stone retropulsion).

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512333/1 01/10/2017 30/09/2021
1947205 Studentship EP/R512333/1 01/10/2017 30/09/2021 Harry Charles Reynolds