Prenatal Diagnosis of Severe Fetal Hydronephrosis Due to Pyeloureteral Junction Syndrome with False Neonatal Resolution

A case of severe fetal hydronephrosis due to isolated bilateral stenosis of the pyelo-ureteral junction was diagnosed at our centre. Surprisingly, a negative renal ultrasound scan was performed on the 3rd postnatal day. An ultrasound follow-up showed severe bilateral pyelectasis a few weeks later. The infant underwent bilateral pyeloplasty at six months of age with an excellent outcome. Such a neonatal picture may be due to the reduction of urinary output secondary to excessive postnatal weight loss and dehydration. In this case, prenatal ultrasound result was more reliable than postnatal ultrasound, emphasizing the importance of postnatal urologic follow-up after prenatal indication.