What electrolyte abnormality is most characteristic of Addison’s disease in dogs?

• A. Hyponatremia with hyperkalemia.
• B. Hyponatremia with hypokalemia.
• C. Hypernatremia with hyperkalemia.
• D. Hyperkalemia with hypochloremia.

Answer: (A)

The key idea is how aldosterone deficiency in Addison’s disease alters kidney electrolyte handling. Without enough aldosterone, the distal nephron reabsorbs less sodium and excretes less potassium, so sodium is lost in the urine and potassium builds up in the blood. This creates hyponatremia and hyperkalemia, which is the most characteristic electrolyte pattern seen in canine primary hypoadrenocorticism. Chloride often follows the sodium down, and mild acidosis can occur, but the hallmark is low sodium with high potassium.