Urinary bladder dysfunction affects millions worldwide. It adds burden to the healthcare system and individual patients with surgeries and long-term treatments such as daily catheterization. Patient specific modelling has been shown to reduce healthcare costs. Computational models are based on mechanical properties of tissues and can help in diagnoses or treatment plans. Although much work has been done on organs such as brain and heart, work on the urinary bladder is scarce. The bladder is a complex organ that exhibits time dependent behavior and so many factors must be considered when studying its mechanical properties. Researchers face challenges in replicating others' experiments, isolating constituent behavior, identifying pathological causes of mechanical behavior, and modelling the viscoelasticity. We focus on two issues that will improve computational models of the urinary bladder wall. The first issue is to identify differences in mechanical behavior based on anatomical location and bath osmolarity. The second issue is to find an appropriate viscoelastic constitutive equation. Parameter characterization of viscoelastic models is especially challenging due to the time dependence of certain parameters. We explore the methods applied in literature and propose four possible models that would be appropriate for our experiment. The models reveal that for best results, we must normalize our data, choose an appropriate relaxation spectrum that has a unique solution, and consider nonlinear elasticity in addition to viscoelasticity. Preliminary results from these models suggest that the lower body and trigone regions of the bladder have lower compliance than other regions. Our models also indicate a change in compliance based on bath osmolarity. In the future we will improve these results for definitive parameters that can be compared statistically. We will do this through the implementation of nonlinear elastic viscoelasticity and triphasic theory.
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