The widespread use of antenatal ultrasound (US) in the last 25–30 years has allowed the early identification of a number of congenital nephrourological abnormalities, which are now assessed with imaging soon after birth. In addition, a congenital nephrourological abnormality may declare itself postnatally, for example, with a urinary tract infection, anomalies in urine stream, septicemia, metabolic upset due to renal failure, or simply vomiting. Occasionally, the neonate may have hematuria due to renal vein thrombosis, especially in the case of a prolonged labor with hypoxic events. A healthy neonate may present with an abdominal mass found on routine examination or with an apparently unrelated congenital abnormality, e.g., esophageal atresia.