CTT on Renogram as an Early Marker of Significant Obstruction in Uretero-pelvic Junction Syndrome

Inclusion Criteria: Infants: * Aged of 4 to 8 weeks of life * Presenting an ureteropelvic junction obstruction (UPJO) detected before birth by ultrasound * Presenting an UPJO, defined by an Antero-Posterior Renal Pelvic Diameter greater or equal to 15 mm, confirmed by ultrasound post-natally between the 1st and 15th day of life * Presenting a unilateral UPJO * whose legal representatives have provided a signed free and informed written consent for their infant's participation * whose at least one of his legal representative is affiliated to national social security Exclusion Criteria: Infants presenting: * A bilateral UPJO * An ureteral dilatation * An associated contralateral uropathy * A solitary kidney * A renal insufficiency * Severe associated disabilities ( ie polymalformation syndromes) * A concomitant participation in another trial * A contraindication to furosemide (acute renal insufficiency, hepatic encephalopathy, hypovolemia or dehydration, severe hypokalemia, severe hyponatremia) * A contraindication to the radionuclide marker (hypersensitivity to the active substance or to excipients)