Successful management of paediatric chronic SIAD with oral urea: report of two cases

Syndrome of inappropriate antidiuretic hormone secretion (SIAD) causes euvolemic hyponatraemia and is managed with fluid restriction, which can be difficult to maintain in children with chronic disease. Urea is an osmotic diuretic recommended as a second-line therapy, but paediatric experience remains limited.

Patient 1 was a 1-year-old male infant diagnosed with SIAD secondary to an optic pathway pilocytic astrocytoma, following therapeutic exposure to carboplatin and vincristine/vinblastine. Initial management with fluid restriction and sodium supplementation proved insufficient, resulting in persistent hyponatraemia and compromised physical growth. Crucially, because the patient's nutritional intake was derived primarily from milk, standard fluid restriction inherently imposed severe nutritional restriction. Following the introduction and gradual titration of urea therapy, plasma sodium normalised, urine output increased and sodium supplementation was discontinued. This clinical improvement allowed for the liberalisation of fluid intake, thereby restoring adequate nutritional delivery and subsequently improved growth. Patient 2 was a 16-year-old girl with severe neurological impairment, panhypopituitarism and chronic SIAD following neonatal meningitis and hypoxic-ischaemic injury. Her hyponatraemia persisted despite fluid restriction and sodium supplementation, and prolonged restriction probably contributed to renal calcium cysts. After starting urea, plasma sodium normalised, fluid restriction was eased and sodium supplementation was discontinued.

In conclusion, oral urea represents a safe, cost-effective maintenance therapy for paediatric chronic SIAD. By mitigating strict fluid restriction, it facilitates adequate nutritional delivery essential for growth. Additionally, its minimal potential for drug-drug interactions offers a distinct practical advantage in medically complex children.