Dismembered pyeloplasty followed by metachronous ureteropelvic junction obstruction in the contralateral kidney.

Hydronephrosis due to congenital ureteropelvic junction obstruction (UPJO) is commonly diagnosed by antenatal sonography. We report the case of an infant who developed new-onset hydronephrosis in the right kidney following uneventful left-sided pyeloplasty for a congenital UPJO. The furosemide minus 15-minute diuretic renogram (F-15 DR) was used to confirm obstruction in the affected renal unit when standard diuretic renography was equivocal. The indications for surgery or observation as well as the role of the F-15 DR are discussed.