Peristaltic activity in the normal renal pelvis of the pig during standardized perfusions.

The peristaltic activity in 36 normal pig pyeloureters in 19 pigs was investigated during various steady flow rates. Flow rates of 2, 4, 6, 8, 10 and 20 ml/ureter/min resulted in a mean frequency of 4.5, 4.9, 4.4, 4.2, 4.2 and 5.1 peristaltic events/min respectively. The frequency of peristalsis was thus independent of flow rate and also of baseline pressure but showed a weak relation to the magnitude of the mean perfusion pressure. The peristaltic activity is generally constant at all physiological flow rates in the steady state. This standardized study therefore confirms previous observations in showing that urine transport mainly is regulated by changes in the bolus size.