CHARACTERISTICS AND MECHANISM OF PYELORENAL BACKFLOW CORRELATED TO RENAL PELVIC PRESSURE

Abstract

The present study was conducted to examine the characteristics of pyelorenal backflow related with the changes in renal pelvic pressure. Forty rabbits weighing approximately 3.0kg were used in this experiment. The renal pelvis was continuously perfused with PSP solution through the double lumen catheter placed above the ureteropelvic junction. The renal pelvic pressure was also recorded during the intrapelvic perfusion. Simultaneously, PSP concentrations in blood and urine excreted from the contralateral kidney were measured.
During the intrapelvic perfusion with PSP solution, PSP blood concentration began to increase immediately and reached maximum within 1 or 2 minutes after a start of perfusion. Then, its concentration gradually decreased toward the constant, low levels. The urinary concentration of PSP showed the same change as the blood concentration with a time lag of 1 or 2 minutes. A compartment analysis showed that this backflow curve composed of an early phase and a late phase. The early phase was characterized by a rapid increase and following decrease (exponentially declining) in PSP concentration. The late phase was a portion of constant PSP concentration in the backflow curve.
A maximum PSP concentration in the early phase was elevated with an increase in the increment rate of renal pelvic pressure. There was a significant, positive correlation between the maximum PSP urinary concentration and the increment rate of renal pelvic pressure (dp/dt). The constant values of PSP concentration in the late phase could be correlated with neither increment rate nor absolute values of renal pelvic pressure.
It seems from these results that in the early phase, a passive transport plays an important role in dynamics of pyelorenal backflow because and extent of reflux depends on the changes in renal pelvic pressure. The late phase of backflow may result from an active transport system in the perfused kidney. However, further studies are necessary to clarify this late component of backflow.