Experimental study of the pressure-volume and pressure-time relations in the completely obstructed pelvis of the porcine kidney. Part 2: The relation between actual hydrostatic pressure, intrapelvic volume and time.

In a series of experiments with pigs the completely obstructed renal pelvis was infused with Ringer's lactate at a constant rate of 2 ml/min. At various pressure levels (lower than 50 mm Hg) the relations pressure vs infused volume and pressure vs actual intrapelvic volume and the effects on the intrapelvic pressure of rapid total or partial extraction of the actual volume were measured. At pressure levels lower than 15-20 mm Hg the P-V relation is exponential; at pressure levels between approximately 20 to 50 mm Hg this relation is linear. In the pressure range from 20 to 50 mm Hg the pressure decays, at a constant or increasing volume, asymptotically to a certain stabilisation value when the infusion is stopped. The relation between stabilised pressure and intrapelvic volume is linear.