In vitro study of age-related changes in human ureteral failure properties according to region, direction, and layer

Abstract

Knowledge of the capacity of the ureteral wall to withstand urodynamic or external stresses is essential to understand ureteral injury and rupture that mostly occur following trauma, but may also be secondary to obstructive uropathy. It has clinical significance as well in the prevention of iatrogenic injury, for example, during ureteroscopy, but no information is available with regard to the age-related failure properties and regional differences have not been systematically described. Uniaxial tensile testing was performed on 166 ureteral rings and strips from 21 humans free of overt urologic disease; histological evaluation was performed. The degree of layer participation to the intact wall failure stress (=tissue strength), peak elastic modulus (=stiffness), and failure stretch (=extensibility) was assessed by examining layer-specific ruptures in the stress–stretch data. Failure stress at and peak elastic modulus before the first (muscle/adventitial) rupture correlated inversely less with age ( p < 0.05 in few regions/directions) than failure stress at the second (mucosal) rupture ( p < 0.05 in the middle and lower ureter), consistent with the decreased mucosal thickness in ≥50-year-old subjects. Failure stretch at both ruptures did not correlate with age ( p > 0.05 in most regions/directions), paralleling elastin content. Correlations with age were more significant in females than males. Failure stress at the second rupture point was higher ( p < 0.05) distally in <50-year-old but not in ≥50-year-old subjects, justified by the increased collagen distally in the former. Directional differences in failure stretches ( p < 0.05 at all ages/regions/genders) were justified by preferentially axial collagen reinforcement. The presented results may establish the foundation for computational models of iatrogenic/accidental ureteral trauma.

Fluid mechanical modeling of the upper urinary tract

“…In terms of the material properties of the ureter wall, Rassoli et al (2014), Sokolis et al (2017), Sokolis (2019, 2020) are among the few who provided studies on the strain–stress properties of human ureters. In a complementary approach, Toro and Siviglia (2013) formulated a one‐dimensional time‐dependent nonlinear mathematical model for collapsible tubes with discontinuous mechanical properties.…”

Development and validation of a predictive model for failure of ureteral access sheath placement in patients with ureteral calculi

“…This may be related to the mechanical characteristics of the ureter itself [19]. It has been found that with age, the ureter undergoes remodeling secondary to histomorphometry changes, mainly consisting of an increase in ureteral circumference, wall thickness, length and Cross-Sectional Area (CSA) [20,21]. At the same time, it was found that UAS insertion force (UASIF) increased with increasing dilator or access sheath size, and some variations could be observed according to age and gender; for example, a decrease in median maximal UASIF at the PUJ and VUJ was observed in patients aged >70 years, and lower median maximal UASIF at the PUJ in women than in men was reported [22,23].…”

Mechanical characterization of porcine ureter for the evaluation of tissue-engineering applications

“…Decellularized tissues are expected to promote cells growth and In the present work, the mechanical behaviour of the porcine native ureter was investigated to evaluate its potential application in clinics for the substitution of tubular tissues such as the ureter and blood vessels, through ring and membrane flexion tests. These tests were not reported in literature before, except for ring tests performed on human ureters to investigate the contributions of single layers (collagen, elastin and muscle fibres) to tissue resistance (Sokolis, 2019). Other studies have reported a mean ultimate tensile strength of 2.31 MPa in the circumferential direction (Rassoli et al, 2014) and 5.02 MPa in the same direction, specifying the distal region (Shilo et al, 2014).…”

“…Until now, mechanical tests on ureters have been performed in humans ( Rassoli et al, 2014 ; Shilo et al, 2014 ; Sokolis, 2019 ) and different animal models ( Yin and Fung, 1971 ; Weiss et al, 1972 ), but only few data were reported for porcine model. Uniaxial tests were performed along the circumferential and longitudinal directions to evaluate the tensile strength and longitudinal direction was stiffer than circumferential one ( Van Mastrigt et al, 1981 ).…”