Regional differences exist in elastic wall properties in the ureter.

According to classical mechanical theory, the passive elastic properties of a distensible tube are important for the resistance to flow. The aim was to study luminal dimensions under pressure loading and the tension-strain distribution of the ureter in anaesthetized pigs by means of impedance planimetry. Stepwise inflation of an intraluminal balloon in which the cross-sectional area (CSA) and pressure were measured provided the distension stimulus in the ureteropelvine junction, in the midureter and in the intramural part of the ureter at the ureterovesical junction. The circumferential tension-strain distributions were computed from steady state values of these measurements. The CSA always reached equilibrium within the two-minute distension period. The steady state pressure-CSA curves were nonlinear and differed between the three measuring points (p < 0.001). The most pronounced difference was found between the ureteropelvine junction and the two other measuring points. At the lowest applied pressure of 1 kPa the steady state CSA was 15.4 +/- 1.1, 16.6 +/- 1.1, and 19.9 +/- 19.9 mm2 in the intramural part, middle part and ureteropelvine junction, respectively. At the maximum pressure the figures were 41.9 +/- 2.9, 47.0 +/- 2.7, and 73.1 +/- 8.2 mm2 for the three locations, respectively. The circumferential tension-strain distributions were nonlinear with an exponential-like behaviour. The tension-strain curve obtained from the ureteropelvine junction was translated to the right compared to the curves obtained from the two other measuring points (p < 0.05) indicating that the ureteropelvine junction was more compliant than the two other locations.