The influence of pyeloureteral peristalsis on pelvic pressure during increase in flow rate.

Thirty-nine normal pig pyeloureters were perfused with 0, 2, 4, 6, 8, 10 and 20 ml/min during continuous measurement of the pelvic pressure. A phasic pressure response was identified with the highest pressure increase between 2 and 4 ml/min. Two groups were analyzed. One consisting of the 10 pyeloureters with the highest pressure increase and the other of the 10 pyeloureters with the lowest pressure increase to a perfusion rate of 4 ml/min. The peristaltic frequency was significantly higher (about 6/min) in the high pressure group than in the low pressure group (about 3.5/min). It is concluded that a high peristaltic frequency is at least partly responsible for the high pressure response to increasing flow because the peristaltic contraction ring opposes the filling flow through ureter.