10% of patients with hypertension potentially have the treatable condition - primary aldosteronism. Primary aldosteronism (PA) is caused by either bilateral adrenal disease (~40%), managed with lifelong medications; or unilateral disease (~60%), cured with laparoscopic surgery (adrenalectomy). Unfortunately, many patients with curable hypertension remain undiagnosed and consequently develop cardiac disease and strokes. The difficulty with identifying curable unilateral disease is due to adrenal vein sampling (AVS): an invasive, and technically-difficult procedure, with inconclusive results in 50% of patients. An alternative novel imaging, 11C-metomidate Positron emission tomography-computed tomography (PET-CT), can detect adrenal tumors, and concurrently confirm their over-activity. It is non-invasive, non-operator-dependent, and can identify more patients with curable hypertension.

Investigators hypothesize that 11C-metomidate PET-CT can accurately identify patients with surgically-curable unilateral adrenal disease among hypertensive Asians with primary aldosteronism.

25 patients with confirmed PA who are keen for a surgical cure if unilateral PA is confirmed, will undergo conventional tests, CT, AVS, as well as 11C-metomidate PET/CT.

Results will be reviewed and discussed at a multidisciplinary meeting, and patients with unilateral PA will be offered surgery. Patients will be reviewed 6 months post surgery to assess for cure of PA.

Inclusion Criteria:

• Primary aldosteronism, as defined in Endocrine Society Guidelines 2016, with positive confirmatory test (post-salt loading aldosterone >140pmol/L); or hypokalemia with undetectable renin levels and aldosterone >550pmol/L.

Exclusion Criteria:

• Inability to provide written informed consent
• < 21 years or > 70 years
• Chronic renal failure of Stage 3b or greater severity
• Severe or terminal medical condition(s)
• Contraindications to isotope scanning or CT Scan
• Contraindication to ingestion of corticosteroids