The pressure volume relationship of the renal pelvis in total obstruction in pigs.

The renal pelvic pressure/volume relationship was investigated in 8 pigs with a 10-week total unilateral obstruction. The pressure in the totally obstructed pelves was significantly increased to a mean value of 44 cm H2O (30.5-64). After emptying, the renal pelves were refilled continuously at a rate of 8 cc per minute to a maximal pressure of 80 cm H2O. The relationship between pressure and volume showed a cystometric configuration. Capacity at the maximal pressure varied from 32 to 167 ml. The difference in capacity was not related to differences in the pelvic wall connective tissue fraction or the wall thickness. Neither was any relation between resting pressure and capacity found. The investigation demonstrates that total supposedly uniform obstructions exhibit a broad variation in compliance. The broad variation in compliance might be an important factor in the pathogenesis of progression in hydronephrosis.