Chronic ureteric obstruction and its impact on the coordinating mechanisms of peristalsis (pyeloureteric pacemaker system).

We present the results of a study designed to characterise urine transport in the healthy and chronically obstructed upper urinary tract. Fifteen healthy and 11 hydronephrotic pigs were used; experimental hydronephrosis was produced by partially obstructing the ureter. Data consisting of the peristaltic rate, bolus volume, and the urine flow rate were collected and related to varying increments of diuresis. The transmission characteristics of renal pelvic to ureteric contractions were studied by extracellular electrodes. Similarly, in hydronephrotic preparations we studied the transmission between the proximal and middle pelvis to the ureter. In healthy preparations, the contraction frequency of the renal pelvis and the ureter is identical, while in obstructive cases, the contraction frequency of the upper pelvis is not coordinated with the lower pelvis or ureter. While diuresis increased bolus volume to a maximum of 1,200% in the healthy and 660% in the hydronephrotic kidney, the peristaltic rate changed by only 45% and 50% respectively. The results of this study show that chronic ureteric obstruction alters the coordination of ureteric peristalsis and thereby disrupts the pacemaker mechanisms of the renal pelvis.