A 10-year-old neutered male domestic shorthair cat was presented for investigation of chronic vomiting, anorexia and progressive polyuria/polydipsia over a period of 3 weeks. The referring veterinarian performed an abdominal ultrasound, which revealed a mass with a diameter of 3 cm near the right kidney. Physical examination was unremarkable. Given the chronic vomiting, anorexia, polyuria/polydipsia and the abdominal mass, biochemistry, complete blood count (CBC), urine analysis and blood pressure measurement were performed. Biochemistry revealed moderate azotaemia (serum creatinine 234.3 μmol/l, reference interval [RI] 70.7–212.2) and hypokalaemia (2.9 mmol/l, RI 3.5–5.8). Urinalysis showed low urine specific gravity (1.012). CBC was unremarkable. The mean systolic blood pressure was over 220 mmHg (RI 80–160) when measured by Doppler sphygmomanometry. An abdominal ultrasound revealed a right adrenal mass measuring 3.5 cm (). The contralateral (left) adrenal gland was below the RI (approximately 0.2 cm in height, RI 0.35–0.45) (). The right kidney was small (2.8 cm, RI 3–4) and irregular. The left kidney was enlarged (5.1 cm). Given the clinical presentation, biochemistry and abdominal ultrasound findings, a serum aldosterone test was run and was found to be severely elevated (>5000 pmol/l, RI 87–224), which was compatible with primary hyperaldosteronism. The cat received potassium supplementation (4 mEq K/cat PO q12h; K for Cat, MP Labo), spironolactone (2 mg/kg PO q12h; Prilactone Next 10 mg, Ceva) and amlodipine (1.25 mg/cat PO q24h; Amodip, Ceva) for 1 month preoperatively. One week after starting medical therapy, serum potassium and blood pressure were within the normal range (4 mmol/l and 150 mmHg, respectively). Thoracic, abdominal and brain CT were performed before surgery to assess for possible vascular invasion of the adrenal mass and possible lung and/or cerebro meningeal metastasis. The adrenal mass was 5–6 cm in diameter, encompassing the right kidney with adhesions to the caudal vena cava and abdominal aorta ( and ). The cat received enoxaparin (100 UI/kg SC q8h; Lovenox, Sanofi) 48 and 24 h before surgery, as well as on the day of the procedure. Methadone (0.2 mg/kg IV; Comfortan, Dechra), midazolam (0.3 mg/kg IV; Mylan) and propofol (4 mg/kg IV; Proposure, Axience) followed by isoflurane gas with tracheal intubation were used for the general anaesthesia. A xyphopubic laparotomy allowed visualisation of a right adrenal mass of 5 cm in diameter, firmly attached to the right kidney, caudal venal cava and abdominal aorta. Soft tissue dissection allowed a monobloc resection of the mass (adrenal gland and right kidney) after ligation of the phrenico-abdominal vein, the renal vein, a branch of a right hepatic vein and the renal artery (). The mass was dissected off the aorta and vena cava to enable en-bloc resection. The right ureter was ligated and removed. The rest of the laparotomy did not identify any other abnormalities. Histopathological analysis revealed a corticoadrenal carcinoma (LAPVSO) (). Histopathological analysis revealed a cortico-adrenal carcinoma (Laboratoire d’Anatomie Pathologique Vétérinaire du Sud-Ouest [LAPVSO]) (). Buprenorphine (0.02 mg/kg IV q8h; Vetergesic, Ceva) was given for 3 days postoperatively. Twenty-four hours after surgery, the cat became more alert. Electrolytes, serum creatinine and blood pressure had normalised (,). Prednisolone (0.5 mg/kg then 0.28 mg/kg PO q24h; Dermipred, Ceva) was also given. At postoperative day 4, an increase in serum creatinine was observed (218.3 µmol/l) and blood pressure was normal (140 mmHg). At postoperative day 25, the cat was clinically normal, and serum potassium, creatinine and blood pressure were stable (4.2 mmol/l, 180.3 µmol/l and 152 mmHg, respectively) (,). At postoperative day 70, the cat vomited three times a week over a period of 10 days and serum creatinine increased (358 µmol/l) (). Serum potassium also increased (6.9 mmol/l), with a low Na:K ratio (23, RI >27) (,). An adrenocorticotropic hormone (ACTH) stimulation test was performed and a normal response was observed (pre-ACTH cortisol 41.4 nmol/l, post-ACTH cortisol 144.2 nmol/l, RI 40–138). Serum aldosterone was less than 20 pmol/l (RI 87–224), compatible with hypoaldosteronism. Desoxycorticosterone pivalate was administered at 1.5 mg/kg SC (Zycortal, Dechra) and glucocorticoid supplementation was continued (prednisolone, 0.28 mg/kg PO q24h; Dermipred, Ceva). At 15 days after injection, normonatraemia and normokalaemia, with a normal Na:K ratio of 29, were observed. Serum creatinine had decreased to 315.6 µmol/l but was still elevated. One month later, a second injection of desoxycorticosterone pivalate was administered at the same dosage. Serum creatinine and potassium were 371.3 µmol/l and 5.2 mmol/l, respectively, with an Na:K ratio of 31 () supporting an appropriate dosage interval. The interval between two injections was considered correct. A total of six injections of desoxycorticosterone pivalate were needed, with one injection every 4 weeks. Prednisolone was tapered then stopped 6 months postoperatively (). At 920 days after diagnosis and 640 days after the last desoxycorticosterone pivalate injection, the cat was clinically normal with serum potassium and sodium within the reference interval (K 4.3 mmol/l, Na 150 mmol/l, Na/K 35) () but persistently elevated creatinine.