Background

Hyponatremia is one of the most common electrolyte imbalances in human patients with central nervous system disorders. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral salt-wasting syndrome (CSWS) are the most common causes of hyponatremia in patients with neurological problems. CSWS is characterized by hypotonic hyponatremia associated with hypovolemia. To date, no cases of CSWS have been described in the veterinary literature.

Case Presentation

A 3-year-old, female, neutered, mixed-breed dog was referred because of a chronic-progressive history of disorientation, incoordination and circling. The physical examination was within normal limits. The neurological examination showed obtundation, hyperexcitability, pacing, circling, hypermetric gait of the four limbs, and bilaterally absent menace response. The neurological anatomical localization was a diffuse intracranial disease mostly involving the left prosencephalon, the brainstem and the cerebellum.

The most likely differential diagnosis was an anomalous-congenital disorder, such as hydrocephalus. Complete blood and urinary tests were within normal limits. The magnetic resonance imaging of the brain showed severe congenital hydrocephalus.

A ventriculoperitoneal shunt was applied. After the surgical procedure, the dog was referred to the intensive care unit for postoperative care. Immediately after the surgery, the patient entered a hypovolemic state due to an increased diuresis, despite the intravenous fluid administration. Two days after surgery the patient developed a moderate/severe hyponatremia. The laboratory analysis ruled out metabolic causes of hypovolemic hyponatremia. The serum and urine osmolality and the fractional excretion of sodium were consistent with the CSWS. Thus, a 3% hypertonic saline intravenous and an oral salt supplementation were initiated. These therapies allowed for a partial resolution of the hypovolemic hyponatremia. An optimal fluid balance and a complete correction of the electrolytic disturbance were achieved only with fludrocortisone treatment.

New/Unique Information

To the author’s knowledge, this is the first case report of CSWS in veterinary medicine. In human medicine, the etiology of CSWS is still debated. CSWS is most commonly described in human patients affected by aneurysmal subarachnoid hemorrhage and less frequently as a consequence of other central nervous system disorders pathological conditions or surgeries. In this case, an acquired condition secondary to the surgery was suspected.

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