Background: Most congenital anomalies of the urinary tract present with hydronephrosis due tornseveral reasons. Some are physiological and others were pathological which persists for morernthan a year. Ultrasound, maturating cystourethrography, dynamic renal scintigraphy andrnintravenous urography , Dynamic and static MRU were used for examination. Currently renalrnarterial Doppler resistance index is not established as a clinically important diagnostic modalityrnto differentiate obstructive and non obstructive hydronephrosis as observed in many conflictingrnresearch results.rnObjective: To assess the usefulness of Doppler ultrasound measurement of resistive index (RI) inrndifferentiating obstructive from non-obstructive hydronephrosis in children.rnMethods: Forty two infants and children (