Design, validation and testing of an in vitro bladder flow simulator

Abstract

Ureteral jet patterns and the resulting intravesical flow may offer fluid-dynamic biomarkers of urinary system dysfunction, however in vivo measurements offer limited access to the full flow field. This thesis presents the design and validation of an in vitro bladder flow simulator that is compatible with both ultrasound and particle image velocimetry (PIV), enabling controlled studies of bladder flow dynamics as a function of various conditions of the urinary system. The platform combines an adult-sized silicone bladder phantom mounted in an optically clear chamber, dual syringe-driven ureteral inlets actuated by programmable linear motors to reproduce a range of jet morphologies, and intravesical pressure sensing. Stepwise filling from 256 to 286 mL produced a nearly linear pressure–volume response from 0 to 13.26 mmHg, with a global elastance of 0.44 ± 0.01 mmHg·mL⁻¹ (compliance of 1.66 ± 0.02 mL·cmH₂O⁻¹), indicating reproducible, volume-independent stiffness over the tested range. Color and pulsed Doppler ultrasound were then used to characterize three physiologically motivated ureteral jet programs. Biphasic jets (healthy case) attained ejection durations of 3.8 ± 0.3 s (4.00-s target) while reproducing programmed peaks of 20 to 90 cm·s⁻¹ to within 3 cm·s⁻¹ (≤ 8%). Monophasic jets (rarer physiological events) yielded 3.3 ± 0.2 s ejection durations (3.50-s target) with 20–30 cm·s⁻¹ peaks within 9% of the target. Continuous jets (pathological case) produced 4.9 s ± 0.2 s plateaus (5.00-s target) at 10–25 cm·s⁻¹ with 6– 15% velocity error. These values and waveform morphologies closely matched published human recordings in the literature, confirming that the simulator can reproduce both normal and dysfunctional ultrasound signatures. Planar PIV in a water–glycerin medium was used to study intravesical velocity, vorticity, and viscous energy dissipation fields for the same three inflow waveforms. Biphasic waveforms concentrated kinetic energy and dissipation into two brief bursts, with a peak speed of 38.60 cm·s⁻¹ and a peak local dissipation of 170 W·m⁻³. The bursts drove rapid jet penetration and vigorous mixing. A transitional (moderately biphasic) program redistributed shear into a spatially longer high-shear region with lower peaks (30.61 cm·s⁻¹) but more sustained recirculation at the upper bladder wall. The continuous program yielded the lowest instantaneous dissipation, with spatial maxima of only 25–30 W·m⁻³, yet maintained a moderate jet shear for the longest portion of the ejection, with intravesical peak velocities around 16.05 cm·s⁻¹ and large regions of slow recirculating flow along the walls. Together, these results demonstrate that the proposed simulator can link clinically-accessible ultrasound signatures to intravesical flow metrics and provides a modular platform for future studies.

Date	12 Dec 2025
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Giuseppe Di Labbio (Supervisor) & Naeem Bhojani (Co-supervisor)