Hypoaldosteronism in a dog with severe hyponatraemia and hypochloridaemia progressing to hypoadrenocorticism

Abstract A 2‐year‐old, male, neutered Siberian husky mixed dog was presented for polyuria, polydipsia, decreased mentation and weight loss for a period of 2 months. Initial diagnostics revealed severe hyponatraemia, hypochloridaemia and hyperkalaemia. An adrenocorticotrophic hormone stimulation test excluded hypocortisolism; however, baseline and post‐adrenocorticotrophic stimulation aldosterone concentrations were consistent with aldosterone deficiency. Renin concentrations were not measured. During hospitalisation, the electrolytes were carefully corrected to avoid metabolic complications. Fludrocortisone was used to treat the mineralocorticoid deficiency, and there was further improvement in the electrolytes as well as resolution of clinical signs. Long‐term, the dog was successfully managed with deoxycorticosterone pivalate. The dog later progressed to possible secondary iatrogenic (suppression of HPA axis by fludrocortisone) or natural hypoadrenocorticism 8 weeks after discharge. Hypoaldosteronism should be a differential in patients with hyponatraemia, hypochloridaemia and hyperkalaemia, even if hypocortisolaemia is excluded. Although rare, hypoaldosteronism can occur in the absence of cortisol deficiency, but progression to hypoadrenocorticism can occur.