Blunt renal trauma in occult congenital hydronephrosis.

Since the routine use of antenatal ultrasonography, congenital pelviureteric junction (PUJ) obstruction rarely presents as an incidental diagnosis following renal trauma. Gross haematuria following seemingly trivial trauma should arouse the suspicion of a pre-existing abnormality. We report a 14-year-old girl with previously asymptomatic and undetected PUJ obstruction who first presented with gross haematuria following a trivial fall. The diagnosis was established by an abdominal computed tomography that showed left chronic hydronephrosis, and was subsequently confirmed on a renal isotope scan. Since the pre-existing hydronephrosis has little impact on the recovery from the injury itself, the initial management was non-operative with an aim to conserve the kidney. As standard surgery has a good outcome, once the renal scan confirmed good renal function, a delayed Anderson-Hynes' pyeloplasty was performed following healing of the kidney laceration as seen on ultrasonography.