Case summary A 10-year-old neutered male domestic shorthair cat was presented with an abdominal mass, associated renal failure, chronic vomiting, anorexia and progressive polyuria/polydipsia lasting for 3 weeks. Clinical examination and initial blood work revealed azotaemia, hypokalaemia and hypertension. Abdominal ultrasound showed an adrenal mass with a diameter of 3 cm near the right kidney. High serum aldosterone suggested primary hyperaldosteronism. Surgery enabled identification of the mass and its excision along with the right adrenal gland. Histologically, carcinoma of the adrenal cortex was diagnosed. Postoperatively, an increase in serum creatinine and potassium, along with a low serum aldosterone, led to a diagnosis of hypoaldosteronism. Mineralocorticoid therapy for 6 months was necessary, resulting in clinical and biological improvement.

Relevance and novel information To our knowledge, this case describes the longest-lasting reported secondary hypoaldosteronism in a cat, after unilateral adrenalectomy for an adrenal carcinoma with hyperaldosteronism.