Modeling the influence of acute changes in bladder elasticity on pressure and wall tension during filling

Abstract

Tension-sensitive nerves in the bladder wall are responsible for providing bladder sensation. Bladder wall tension, and therefore nerve output, is a function of bladder pressure, volume, geometry and material properties. The elastic modulus of the bladder is acutely adjustable, and this material property is responsible for adjustable preload tension exhibited in human and rabbit detrusor muscle strips and dynamic elasticity revealed during comparative-fill urodynamics in humans. A finite deformation model of the bladder was previously used to predict filling pressure and wall tension using uniaxial tension test data and the results showed that wall tension can increase significantly during filling with relatively little pressure change. In the present study, published uniaxial rabbit detrusor data were used to quantify regulated changes in the elastic modulus, and the finite deformation model was expanded to illustrate the potential effects of elasticity changes on pressure and wall tension during filling. The model demonstrates a shift between relatively flat pressure-volume filling curves, which is consistent with a recent human urodynamics study, and also predicts that dynamic elasticity would produce significant changes in wall tension during filling. The model results support the conclusion that acute regulation of bladder elasticity could contribute to significant changes in wall tension for a given volume that could lead to urgency, and that a single urodynamic fill may be insufficient to characterize bladder biomechanics. The model illustrates the potential value of quantifying wall tension in addition to pressure during urodynamics.

Quantification of bladder wall biomechanics during urodynamics: A methodologic investigation using ultrasound

“…The non-linear Ogden model may provide improved constitutive modeling capabilities. The fit-parameter “a” in this study was significantly higher than what was found in rabbit bladder strips (Habteyes et al, 2017), perhaps due to differences in species, setup, or because this methodology assumes negligible external pressure on the bladder.…”

“…Strain was the inner perimeter normalized to the inner perimeter at time=60s. A first-order Ogden model was fit to stress-strain data using the method described in (Habteyes et al, 2017). …”

Validation of a real‐time bladder sensation meter during oral hydration in healthy adults: Repeatability and effects of fill rate and ultrasound probe pressure

“…Glass et al showed differences in bladder shape between individuals with and without OAB, and Atesci et al recently demonstrated that changes in bladder shape may contribute to lower urinary tract symptoms in men, which “may be improved if modifiable factors including increased waist circumference and loosening of the urachus are corrected”. Likewise, Habteyes et al demonstrated that during filling the wall stress of the bladder increases significantly during a load. Furthermore, Mutsumoto et al showed an increase in patient‐reported urgency in neuroexcitation using functional near‐infrared spectroscopy of the brain and subject‐reported urgency due to 5 seconds of manual abdominal compression.…”

Adipose-derived stem cells-seeded bladder acellular matrix graft-silk fibroin enhances bladder reconstruction in a rat model

“…It should be noted that the maturity of neovascularization and extent of reinnervation in engineered bladder remain critical obstacles to overcome for the future clinical application of this ASCs-seeded BAMG-SF strategy. More investigations are warranted to examine the generation of a coherent and contracting bladder segment, including video cystogram, uniaxial tension test and bladder wall tension [ 38 ]. More effective ASCs delivery or proangiogenic pretreatments are warranted to achieve a further enhanced angiogenic potential, and experiments with larger sample sizes conducted using diseased bladder models or large animals are required.…”