Effects of swelling and anatomical location on the viscoelastic behavior of the porcine urinary bladder wall

Abstract

The ability of the urinary bladder to perform its physiological function depends largely on its mechanical characteristics. Understanding the mechanics of this tissue is crucial to the development of accurate models of not just this specific organ, but of the pelvic floor overall. In this study, we tested porcine bladder to identify variations in the tissue's viscoelastic characteristics associated with anatomical locations and swelling. We investigated this relationship using a series of stress-relaxation experiments as well as a modified Maxwell-Wiechert model to aid in the interpretation of the experimental data. Our results highlight that tissue located near the neck of the bladder presents significantly different viscoelastic characteristics than the body of the organ. This supports what was previously observed and is a valuable contribution to the understanding of the location-specific properties of the bladder. We also tested the effect of swelling, revealing that the bladder's viscoelastic behavior is mostly independent of solution osmolarity in hypoosmotic solutions, but the use of a hyperosmotic solution can significantly affect its behavior. This is significant, since several urinary tract pathologies can lead to chronic inflammation and disrupt the urothelial barrier causing increased urothelial permeability, thus subjecting the bladder wall to non-physiologic osmotic challenge.