Hydramnion and fetal renal anomalies.

Four instances of hydramnion associated with renal anomalies are reported: two patients had obstructive uropathies and two had a neoplastic type of renal dysplasia. In two infants water concentration tests revealed a defect in water-concentrating ability. It is postulated that the observed hydramnion resulted from fetal polyuria. In patients with unexplained hydramnion a search for renal anomalies is indicated.