Electrolyte composition of the amniotic fluid in Bartter syndrome.

In three patients with neonatal Bartter syndrome associated with polyhydramnios, analysis of the amniotic fluid showed normal sodium, normal-to-low potassium, but high chloride concentrations. This finding clearly suggests a renal chloride reabsorption defect as the primary cause of the neonatal form of Bartter syndrome. It is suggested that whenever polyhydramnios occurs, the electrolyte composition of the amniotic fluid should first be analysed in order to establish the diagnosis of Bartter syndrome.