Describe the presentation and initial diagnostic approach to hyponatremia in a dog.

• A. Signs include confusion, ataxia, and seizures; evaluate serum sodium, assess volume status, identify underlying cause, and plan slow correction.
• B. Hyponatremia always presents with vomiting and diarrhea; immediately give rapid IV fluids.
• C. Hyponatremia is diagnosed by sodium level alone without other assessments.
• D. Hyponatremia presents with pruritus and skin lesions.

Answer: (A)

Hyponatremia in dogs often shows up with neurologic signs because low extracellular sodium leads to brain swelling, so confusion, ataxia, and seizures are typical presentations. The best approach is to confirm the low sodium with a blood test while simultaneously evaluating the patient’s volume status (hypovolemic, euvolemic, or hypervolemic) to guide initial management. A key part of the workup is identifying the underlying cause—dehydration and volume depletion, SIADH-like states, renal failure, Addison’s disease, or diuretic or polydipsia effects—so treatment targets both correcting the sodium safely and addressing the root problem. Plan a slow, monitored correction because too rapid a rise in serum sodium can cause osmotic demyelination, especially if the hyponatremia has been longstanding. Helpful initial testing typically includes serum electrolytes and osmolality, kidney and organ function tests, and urine studies (urine sodium and urine osmolality) to help distinguish whether sodium loss, water excess, or a combination is driving the hyponatremia.

The other statements aren’t correct because hyponatremia does not always present with vomiting and diarrhea, and treatment should not be rapid IV fluids without considering the patient’s volume status and the safe rate of correction. It is not diagnosed by sodium level alone without broader clinical and laboratory assessments, and pruritus with skin lesions is not a typical presentation of hyponatremia.