The elastic behavior of the urinary bladder for large deformations

Area of Science:

• Biomechanics
• Materials Science
• Urology

Background:

• The mechanical properties of the urinary bladder are crucial for understanding its function.
• Existing models, like the Treloar model, are insufficient for accurately describing bladder behavior.

Purpose of the Study:

• To investigate the theoretical basis of urinary bladder pressure-distension.
• To develop a new strain energy function applicable to bladder tissue.

Main Methods:

• Finite strain theory applied to hollow spherical structures.
• Inversion of the pressure-extension ratio relationship to derive a general strain energy function.
• Empirical fitting of the derived function using experimental volumetric pressure-distension data.

Main Results:

• A novel strain energy function, W(lambda, lambda, lambda -2) = C1 (P(1), a) + P(1)C2 (a, lambda)ea(lambda -1), was derived.
• The function was validated using uniaxial loading experiments on bladder strips.
• Good agreement was observed between theoretical predictions and experimental stress-strain data.

Conclusions:

• The developed finite strain theory and derived strain energy function accurately model urinary bladder biomechanics.
• The strain energy function exhibits an exponential nature when plotted against the first strain invariant.
• This model offers a more precise approach to analyzing bladder tissue mechanics compared to existing models.