Pyeloureteral dynamics. Pelvic pressure and kidney function in partial long-term ureteric obstruction.

In 10 pigs with reno-scintigraphically proven normal upper urinary tracts, a standardized partial obstruction of the left ureter was created at the lower kidney pole level. Three weeks later kidney function was scintigraphically reassessed and the pressure flow relationship in the flow range 0-20 ml/min outlined. The partially obstructed pelvic baseline pressure varied from 9.0 to 32.0 cmH2O. During perfusion small increases in pelvic pressure were seen at all flow rates in the individual cases and there was a linear relationship between pressure and flow. Compared to previous results of a similar but acute obstruction the results were identical in pressure ranges and pressure flow profile. This demonstrates, that a longitudinal stability in transport mechanism qualities is present also during the course of obstruction. The pelvic pressure at low flow rates was significantly correlated to kidney function depression, whereas perfusion pressures at high flow rates did not show any correlation, except at 20 ml/min. This clearly indicates, that the pelvic pressure at normal urine flow rate is an important factor in the pathogenesis of obstructive nephropathy.