[Acute symptomatic hyponatremia in a 70-year-old patient. Insufficient ADH secretion syndrome].

CASE REPORT: A 70-year-old male was admitted to the hospital with anorexia, nausea, headache, and apathy. Serologically remarkable were a severe hyponatremia, serum hypoosmolality and urine hyperosmolality with normal renal function. After excluding adrenal insufficiency, hypothyroidism and other possible causes of hypoosmolar hyponatremia, the diagnosis of a syndrome of inadequate ADH secretion (SIADH) was confirmed through a nonsuppressed ADH level and a rise in of serum sodium after fluid restriction. Magnetic resonance imaging showed a small, chronic, traumatic subdural hematoma which was responsible for the SIADH in our patient.

CONCLUSION: This etiologic correlation was reported in literature by many authors. However, these SIADHs were associated with a big subdural hematoma which needed neurosurgical intervention in most of the cases. Our patient is unique in that his symptoms were caused by a small subdural hematoma, which did not need surgical intervention. The patient was treated with cautious saline infusion, administration of a loop diuretic and fluid restriction with improvement of both his clinical and metabolic state. As large water loads may result in severe hyponatremia in these patients, moderate fluid restriction appears to be effective in long-term management even after stabilization/normalization of serum sodium. There are no sufficient data about the incidence of asymptomatic hyponatremia due to SIADH resulting from minor head injury, because most of these patients are asymptomatic and therefore they do not receive clinical attention.