The transport of urine in the upper urinary tract of the multicalyceal kidney was studied in healthy and chronically obstructed pigs in terms of renal pelvic pressure, rate of and coordination of ureteral contractions, and bolus volume. The variations of these parameters to diuresis was examined by incremental elevation of urine output effected by intravenous infusion of mannitol. In 16 healthy animals the mean variation in urine flow was 0.01-3.20 ml/min, the change in peristaltic rate ranged from 0.763 to 5.125 min-1, and bolus volume from 0.003 to 2.083 ml.. In 14 chronically obstructed kidneys, for a mean variation in urine flow of 0.006-5.4 ml/min, peristaltic rate ranged from 0.237 to 6.095 min-1 and bolus volume from 0.00 to 1.80 ml. Discoordinated contractions, bursts of peristalsis, and incompletely transmitted pelvic contractions were characteristic of a chronically obstructed system. These observations are compared with the unobstructed unicalyceal and multicalyceal kidney. The disrupting impact of chronic ureteral obstruction on the hierarchical organization of the pyeloureteral pacemaker system is discussed.
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