The diagnosis of upper urinary tract obstruction in children: comparison of diuresis renography and pressure flow studies.

We report the use of diuresis renography and pressure flow studies to diagnose urinary tract obstruction in 41 collecting systems of 33 children. If differential pressures between the renal pelvis and the bladder in excess of 22 cm. water at a flow rate of 10 ml. per minute is accepted as evidence of obstruction and below 15 cm. water is accepted as normal the interpretation of the renogram showing O'Reilly's pattern IIIa as evidence of stasis without obstruction was correct in 74 per cent of the cases. Likewise, the interpretation of O'Reilly's renogram pattern IIIb as showing partial obstruction was correct in only 40 per cent of the cases. Thus, we urge caution in the use of the diuresis renogram to diagnose or to rule out upper urinary tract obstruction.