Recurrent hyponatremia in neonate: a case of renal salt wasting syndrome

Abstract

Renal salt wasting (RSW) is primarily seen with central nervous disorders and is characterized by hyponatremia, elevated urinary sodium excretion, increased urine output, and hypovolemia. Although there have been reports of RSW in children, it has not been reported in newborns. A term (38 weeks 2 days) female weighing 2060 g, born via normal vaginal delivery, to a primi-gravida mother, was admitted to our neonatal intensive care unit. At birth, the baby was non-vigorous, had aspirated meconium, and required bag-and-mask ventilation following which the baby cried. The child was put on CPAP and inotropes for respiratory distress and shock, respectively, along with first-line antibiotics. Over the next few days, the child was weaned off CPAP, inotropes were stopped, and feeds were started. On postnatal day (PND) 8, the baby developed repeated episodes of seizures requiring two-antiepileptics followed by midazolam infusion, had shock requiring inotropes, and also had a tense anterior fontanelle with altered sensorium and tone changes, for which mannitol and 3% saline were given. Antibiotics were upgraded, and neuroimaging (MRI) revealed left basal-ganglia bleed with intraventricular extension and cerebral venous thrombosis. The baby showed gradual clinical improvement with the above measures and was restarted on feeds. However, from PND-19 onwards the baby had repeated episodes of hyponatremia requiring 3% saline infusions, progressive weight loss, and polyuria. Considering RSW, urine sodium was done which was high (110 mmol/L). For polyuria and weight loss, feed volume was increased, whereas, for hyponatremia, table salt was added to the expressed breast milk (1 gm × tds). Subsequently, all the serum sodium values remained within normal limits, and the baby started gaining weight and was discharged on similar advice (PND 38). On further follow-up, table salt was gradually decreased in the feeds and was stopped after 1 month of discharge with normal serum sodium values. Management of recurrent hyponatremia in a neonate is challenging. Despite its rarity, RSW in newborns should be considered a differential.