ESPE Abstracts

Background: It is sometimes difficult to diagnose and manage fluid and electrolyte imbalance after surgery for hypothalamic/pituitary tumors. We present a pediatric case of severe SIADH successfully treated with tolvaptan after suprasellar tumor resection.

Case: The case was 8-year-old girl with growth failure. She was found to have suprasellar tumor on CT scan when she accidentally fell down and hit her head. MRI suggested a craniopharyngioma. There were no abnormalities in water and electrolyte balance or hormonal data before surgery. Tumor resection by craniotomy was performed and diabetes insipidus was recognized 12 hours after the operation and treated with DDAVP. Serum sodium level gradually decrease to 130 mEq/l without dehydration from the 4th postoperative day (POD) and SIADH was suspected. Water restriction was started but hyponatremia decreased to 126 mEq/l with increasing urinary Na. Dehydration was also noticed on 6th POD, thus 3% saline infusion and intravenous fluids were started with the diagnosis of combined cerebral salt wasting (CSW). The sodium level further decreased to 117 mEq/L. The continuous hypertonic saline and fludrocortisone administration did not improve hyponatremia. We started treatment for SIADH using tolvaptan on POD 8. Three hours after start of tolvaptan administration, serum sodium level increased to 125 mEq/L. Hypotonic polyuria was observed after tolvaptan treatment stopped. CDI was observed afterwards.

Discussion: Triphasic response is known to occur after hypothalamic and pituitary tumor resection. The second phase of SIADH, the duration and severity of this phase is variable and may last from 2 to 14 days. CSW is thought to be an independent phase or extreme condition of SIADH. In this case, it was difficult to diagnose whether the patient had either CSW or SIADH in the postoperative acute phase. The use of tolvaptan promotes free water excretion and may have suppressed the progression of hyponatremia, but it may have been used at the timing of entering DI.

Conclusion: Tolvaptan which is sodium sparing diuretics should be considered in children's severe SIADH with progressive hyponatremia that does not improve with water restriction and sodium load.