The Fluid Mechanics of Ureteroscope Irrigation

Abstract

Purpose: To develop a physical understanding of ureterorenoscopy irrigation, we derive mathematical models from basic physical principles and compare these predictions with the results of benchtop experiments. Mathematical modeling can be used to understand the role of inlet pressure, tip deflection, the presence of working tools, geometric properties of the instruments used, and material properties of the irrigation fluid on resulting flow rate.Materials and Methods: We develop theoretical models to describe irrigation flow in an idealized setup and compare with benchtop experiments for flow through a straight scope, a scope with a deflected tip, and a scope with a working tool inserted. The benchtop experiments were performed using Boston Scientific LithoVue ureteroscope and a variety of Boston Scientific working tools. Standard ureteroscope working channels have circular cross sections, but using theoretical models we investigate whether modifications to the cross-sectional geometry can enhance flow rates.Results: The theoretical flow predictions are confirmed by experimental results. Tip deflection is shown to have a negligible effect on flow rate, but the presence of working tools decreases flow significantly (for a fixed driving pressure). Flow rate is predicted to improve when tools are placed at the edge of the channel, rather than the center, and modifying the cross-sectional shape from a circle to an ellipse can further increase flow rate.Conclusions: A mathematical framework is formulated and shown to accurately predict the properties of ureteroscope irrigation flow. The theoretical approach has significant potential in quantifying irrigation flow and improving ureteroscope design.

A lumped-parameter model for kidney pressure during stone removal

“…The application of mathematical models to improve ureteroscopy is emerging, with Williams et al (2019b), Williams et al (2019a), Oratis et al (2018), and this article providing groundwork for predicting system variables and optimising the design of pertinent biomedical devices. To bring this work closer to clinical translation, several model extensions would be useful.…”

“…We consider steady, unidirectional flows through the working channel and access sheath. The assumption of unidirectional flow through the working channel has been previously validated through comparison with bench-top experiments (Williams et al, 2019b). Steady flow can be justified from the full Navier-0Stokes equations and incompressibility condition by considering flow through a working channel (with a similar discussion for flow through the access sheath).…”

“…Recent efforts have examined the effects of geometric parameters of the ureteroscope and working tools on components of irrigation flow with a mathematical modelling approach (Williams et al, 2019b). Flow through an isolated ureteroscope has been shown, through asymptotic analysis on the small aspect ratio of the working channel, and comparison with bench-top experiments, to obey a Poiseuille law for flow through a cylindrical pipe.…”

An irrigation system for noninvasively estimating intrarenal pressure during flexible ureteroscopy

“…Some researchers analysed the characteristics of fluid mechanics during irrigation and adopted Hagen-Poiseuille's law which has been proven to be feasible. [17][18][19] According to the principle of fluid mechanics, the relationship between proximal irrigation pressure, P prox , and IRP, P ir , can be described as follows: -3 of 11…”

The Effect of Irrigation Fluid Used in Endoscopic Stone Surgery on Infective Processes

“…Bütün ürolojik endoskopik yöntemler esnasında irrigasyon sıvıları kullanılmaktadır. Çeşitli özellikte irrigasyon sıvıları bulunsa da kullanımlarındaki ana amaç; üriner sistemin görüntülenebilmesi, litotriptörlerin fonksiyonel çalışılabilmesi, kırılan taşın ve gelişebilecek kanamaların drenajının sağlanabilmesi, işlem esnasında sistem içi basıncın belli değerler arasında tutulması ve işlem esnasında litotriptöre bağlı gelişen ısının azaltılarak olası komplikasyonların önüne geçilmesidir (1). Bu amaçla endoskopik taş cerrahisinde en çok tercih edilen sıvı %0,9'luk NaCl solüsyonudur.…”