From renal salt wasting to SIADH

Late-Onset Intracranial Hemorrhage Presenting as Refractory Hyponatremia: A Case Report

Here, we report a case of refractory hyponatremia and delayed intracranial hemorrhage following a head injury. A 70-year-old male patient was admitted with complaints of left chest pain and light-headedness after a fall. Hyponatremia recurred despite the correction with intravenous saline. Head computed tomography revealed a chronic subdural hematoma. The subsequent introduction of tolvaptan improved hyponatremia and disorientation. Delayed intracranial hemorrhage is a differential cause of refractory hyponatremia after head contusion. This case is clinically relevant because (i) the diagnostic delay of late-onset intracranial hemorrhage is common but fatal, and (ii) refractory hyponatremia can be a hint of late-onset intracranial hemorrhage.

High Urinary Sodium Concentrations in Severe SIADH: Case Reports of 2 Patients and Literature Review

We present two cases of severe hyponatremia secondary to syndrome of inappropriate secretion of antidiuretic hormone (SIADH) with very high urine sodium concentrations (>130 mmol/L). The first patient had hyponatremia from traumatic brain injury (TBI) while the second case had a history of recurrent SIADH triggered by various causes including gastritis. In both cases, fluid administration and/or consumption worsened the hyponatremia. Although a low urine sodium of <30 mmol/L is highly suggestive of hypovolemic hyponatremia and good response to saline infusion, there is lack of clarity of the threshold of which high urine sodium concentration can differentiate various causes of natriuresis such as SIADH, renal or cerebral salt wasting. Apart from high urine osmolality (>500 mOsm/kg), persistence of high urine sodium concentrations may be useful to predict poor response to fluid restriction in SIADH. More studies are needed to delineate treatment pathways of patients with very high urine osmolality and urine sodium concentrations in SIADH.