Hyperreninaemic hypoaldosteronism in a dog.

A 9-year-old male German shepherd dog was evaluated for clinical and clinico-pathological changes that were suggestive of Addison's disease. On further investigation the basal plasma cortisol concentration was high, a normal cortisol response to ACTH stimulation occurred, plasma renin activity was elevated and low serum aldosterone concentration was present. A diagnosis of hyperreninaemic hypoaldosteronism was made. Replacement fludrocortisone resulted in complete normalisation of the electrolyte and fluid imbalances. Hyperreninaemic hypoaldosteronism has never been reported in the dog.