Primary hypoaldosteronism in a dog with concurrent suspected chronic hepatitis

A 3-year-old female spayed English Cocker Spaniel presented with a 2-month history of lethargy. The owner reported a single tonic-clonic seizure 7 months before presentation and intermittent mild gastrointestinal signs for the past 18 months. Initial investigations revealed hyponatraemia, hyperkalaemia and increased levels of liver enzymes. An adrenocorticotropic hormone stimulation test excluded hypocortisolism. The gastrointestinal signs resolved following a dietary change, suggesting that chronic enteropathy and most primary and secondary causes of hepatic disease were excluded, leaving idiopathic chronic hepatitis as the most likely cause of increased levels of liver enzymes. Liver parameters reduced to levels just above reference range after immunosuppressive doses of prednisolone. Aldosterone levels pre- and post-adrenocorticotrophic hormone stimulation were <20 pmol/litre, consistent with mineralocorticoid deficiency. The mineralocorticoid deficiency was treated with desoxycorticosterone pivalate at 1–1.3 mg/kg subcutaneously every 48–87 days, which resulted in immediate and complete resolution of the clinical signs and electrolyte imbalance. Given the dog's signalment and results from clinical investigations, the isolated hypoaldosteronism is speculated to be caused by immune-mediated adrenal gland destruction. Isolated hypoaldosteronism should be considered a differential diagnosis for hyponatraemia in dogs, when an adrenocorticotrophic hormone stimulation test excludes hypocortisolism.