MON-059 Acute Hyponatremia Following Computed Tomography Radiocontrast in a Pediatric Patient

Hyponatremia is a common laboratory finding. Radiocontrast is hyperosmolar and can draw fluid from the intracellular to the extracellular compartment, but radiocontrast-induced hyponatremia is rare, usually noted in the context of renal insufficiency as a consequence of extracellular expansion exceeding diuresis. We describe an unusual case of 3-year old girl with normal renal function who developed significant hyponatremia following computed tomography radiocontrast. The patient had a mediastinal mixed yolk sac/germ cell tumor and mature teratoma. Imaging was performed with a PET/CT, cardiac CT angiogram, and abdominal CT, for which she received Omnipaque radiocontrast 2 cc/kg. Hyponatremia developed 5 days after administration, with a fall from a baseline sodium of 141 mmol/L to an eventual nadir sodium of 123 mmol/L. An assessment using the serum osmolality of 266 mOsm/kg failed to diagnose hyperosmolar effects of the radiocontrast, with an undetectable concurrent vasopressin level of <0.5 pg/mL. 3% NS boluses failed to have an enduring effect. Without a specific enduring intervention, the hyponatremia then resolved 9 days after administration of the radiocontrast, as the sodium levels remained between 134–139 mmol/L over the subsequent 5 days. Recognition of the clinical scenario and time course of events for radiocontrast-induced hyponatremia is essential for a correct diagnosis. Pediatric patients may be particularly susceptible to radiocontrast-induced hyponatremia given the inherently small size, and following administration of radiocontrast in a pediatric patient, significant morbid hyponatremia is a possible sequalae that should suspected especially if suggestive clinical symptoms present.