Fetal urinoma as a sign of a dysplastic kidney

We describe a female neonate in whom a urinoma was first diagnosed at 20 weeks of gestation without any evidence of underlying urinary tract obstruction. The urinoma became apparent following the performance of a "bloody tap" amniocentesis. Sequential ultrasonography, both fetal and up to 3 months after birth, showed eventual resorption of the urinoma in parallel with the development of a shrunken, non-functioning kidney. Except for the onset of high-renin hypertension, which spontaneously remitted at 1 year of age, the baby's postnatal course was uneventful. Renal function was normal. The presence of a fetal urinoma as a sign of a dysplastic kidney is discussed.