Efficacy of oral tolvaptan for severe edema and hyponatremia in a patient with refractory nephrotic syndrome.

Tolvaptan (TLV) is a vasopressin V2 receptor antagonist that increases free water excretion. However, there are few reports of the use of TLV in pediatric patients with nephrotic syndrome (NS). The efficacy of TLV for the management of edema and hyponatremia in a 12-year-old boy with refractory NS is demonstrated. In this patient, refractory NS developed at 5 years of age, and remission was maintained with several immunosuppressive agents. He was admitted to hospital due to relapse with oliguria, edema, hypoalbuminemia, and hyponatremia. Infusion of human albumin and furosemide did not increase his urine volume, and hyponatremia worsened. Administration of TLV increased urine volume and improved his edema and hyponatremia. There were no adverse effects except for slow elevation of the serum sodium level. Serum osmolality increased gradually, and urine osmolality remained at low levels during TLV treatment. Additionally, a decrease in the sum of the urinary sodium and potassium concentrations was useful to predict the response to TLV and to assess the therapeutic effect of TLV as a biomarker for monitoring. TLV is effective for the management of fluid and electrolyte balance in pediatric NS patients. Early administration of TLV is considered a useful therapy for hyponatremia and refractory edema resistant to other diuretics.