Login to Access Video or Poster Abstract: MP94-04
Sources of Funding: None

Introduction

Knowledge of the mechanical properties of human urethral tissue is required to provide an accurate baseline for urethral graft materials. However, previous studies that characterise urethral tissue under intraluminal pressure are limited to animal models. This is the first study to characterise the baseline passive mechanical properties of human urethral tissue in order to better inform the design of tissue engineered biomaterials intended for use as urethral grafts. Furthermore, this group has previously employed porcine urethras as a rupture model to improve the safety of urinary catheterisation. This study also allows for the validation of such porcine models by determining the threshold inflation pressure of urinary catheter anchoring balloons pertaining to rupture in human urethras.

Methods

Following hospital ethical research committee approval, human urethras were obtained from 9 consenting patients undergoing male to female gender reassignment surgery. The elastic mechanical response of the tissue was characterised by subjecting samples to dynamic cyclical intraluminal pressure (0-10 kPa). The viscoelastic response was characterised by subjecting samples to a static pressure head range (0-10 kPa) and maintaining each pressure increment (1 kPa) for 300s. 12 Fr urinary catheters were then inflated with 10 ml of saline in the bulbar portion of the urethras. Tissue damage was assessed following inflation.

Results

Pressure-diameter testing reveals a nonlinear mechanical response typical of biological tissue whereby the urethral tissue becomes less compliant at higher intraluminal pressures. The mean compliance in the high pressure range (6-10 kPa) under dynamic and static loading was 0.57±0.38 and 1.34±0.55 %/kPa respectively. The increased compliance during static loading demonstrates the pronounced viscoelastic behavior of the urethral tissue. Furthermore, the mean inflation pressure pertaining to urethral rupture during catheter balloon inflation was 165±57 kPa. This is similar to the values obtained from testing of porcine tissue (150 kPa).

Conclusions

This study provides pertinent mechanical data that can be employed to improve the mechanics of tissue engineered urethral graft biomaterials by providing a baseline for both the elastic and viscoelastic response of the native tissue. It also validates an existing porcine urethral rupture model that is aimed at improving the safety of urinary catheterisation.

Funding

None