The relation between pelvic pressure and bladder pressure during pelvic perfusion with standardized flow rates

The aim of this study was to elucidate the relation between pelvic pressure and bladder pressure during pelvic perfusion with standardized flow rates. Anaesthetized Danish Landrace Breed pigs (n = 5) weighing 35-40 kg were studied. Transparenchymally two 6-F catheters were placed in both renal pelves for pressure measurement and perfusion. Transurethrally two catheters were placed in the bladder for pressure measurements and for urine collection and infusion. Bladder filling was done with a constant infusion rate of 45 ml/min during perfusion of both pelves with saline consecutively with the flow rates: 0, 2, 4, 6 and 8 ml/min during continuous measurement of bladder and bilateral pelvic pressure. The baseline diuresis varied from 0.4-1.0 ml/min. Without pelvic perfusion a negative pressure gradient between pelvis and bladder was seen demonstrating the importance of ureteral peristalsis. Pelvic perfusion with 2 ml/min showed that pelvic and bladder pressure were equal demonstrating weakening of ureteral peristalsis. During perfusion with higher flow rates pelvic pressure was higher than bladder pressure, showing that the positive gradient was important for urine transport. In conclusion ureteral peristalsis is important at low flow rates during increasing bladder pressure. At higher flow rates peristalsis weakens and the pressure gradient is the determining factor.