The pressure-volume relationship of the pig renal pelvis

In five pigs weighing approximately 85 kg. the pelvic pressure-volume relationship was investigated. Through a catheter introduced into the renal pelvis from the ureter with ligation at the ureteropelvic junction, a continuous filling of one ml./minute was established. After drainage of the pelvis filling was begun showing an exponential relationship between pressure and volume. Fillings in all of the units confined the equation y = a + bx + cx2. Emptying showed unanimously clockwise hysteresis although 1/3 of the fillings revealed active contractile forces with an inverted S-shaped emptying curve. The normal multicalyceal renal pelvis in pigs of the same size showed a wide range of pressure-volume relationships both between individuals and between the two investigations. This wide range might be of importance in the development of dilatations due to obstruction.