Elastic wall properties and collagen content in the ureter: an experimental study in pigs

We used an impedance planimetric method to look at elastic wall properties of ureter in ten anaesthetized pigs. A balloon was stepwise inflated and deflated in the ureteropelvine junction, in the mid-ureter, and in the intramural part of the ureter at the ureterovesical junction with pressures up to 70 cmH2O, while the pressure and balloon cross-sectional area (Bcsa) were measured simultaneously. The elastic wall parameters were calculated from these measurements. At sacrifice, tissue samples were collected for analysis of collagen content of the ureteral wall. A non-linear clockwise relation (hysteresis loops) between Bcsa and balloon pressure was demonstrated. At maximal inflation of the balloon, the Bcsa, wall tension, and compliance were 35.28 +/- 3.52, 38.44 +/- 3.23, and 61.36 +/- 8.09 mm2, 230.71 +/- 12.82, 242.38 +/- 10.49, and 302.17 +/- 20.03 cmH2O x m, and 0.167 +/- 0.047, 0.124 +/- 0.002, and 0.182 +/- 0.040 mm2 x cmH2O-1 in the intramural part of the ureter, middle part, and ureteropelvine junction, respectively. The collagen content was 0.3249 +/- 0.0077, 0.3301 +/- 0.0066, and 0.3457 +/- 0.0060 mg x mg-1 dry defatted weight in the intramural part, in the middle, and in the ureteropelvine junction, respectively. The collagen content of the ureteropelvine junction was significantly higher than that of the middle of ureter (P < 0.02) and than that of the intramural part (P < 0.05). No significant correlations were found between the elastic parameters at maximal inflation of the balloon and the collagen content (P < 0.10). In conclusion the elastic wall properties were significantly different in the three ureteral segments and the collagen content of the ureteropelvine junction differed from that of the two distal locations. However, no relationship between the wall properties and the collagen content was found.