Neonatal hydronephrosis is an enlargement or dilation of some portion of the collecting system, calyces and-or renal pelvis. This condition is not equivalent to obstruction of the urinary tract, and only a portion of neonates with hydronephrosis subsequently show true obstruction of urine flow due to structural or functional abnormalities. Hydronephrosis is usually detected on prenatal ultrasonography, while neonates or young children with hydronephrosis may occasionally present with a palpable abdominal mass or complications of obstruction such as urinary tract infection or hematuria. Do you want to know more about this condition? Don’t miss this Urology Cheat Sheet!