Conn's syndrome: a simple diagnostic approach

Primary aldosteronism is usually diagnosed after a battery of biochemical tests and adrenal imaging. If an adrenal tumour (Conn's syndrome) is identified, patients need surgery. However, bilateral adrenal hyperplasia is treated medically. Till 1994, we diagnosed Conn's syndrome using simple biochemical tests and a CT scan of the adrenal glands. Aldosterone and plasma renin activity assay became available in our institution in 1994 and were used subsequently in the work up of patients suspected to have Conn's syndrome. We analysed our data to determine whether simple tests such as serum and urinary potassium values combined with CT imaging of the adrenal glands are adequate to arrive at a diagnosis in these patients.

All consecutive patients (n = 17) diagnosed to have Conn's syndrome, managed by the Departments of Endocrinology and Surgical Endocrinology of this institution during a nine-year period from 1990 to 1998, were studied retrospectively.

Until 1994, Conn's syndrome was diagnosed after documenting hypertension, hypokalaemia, inappropriate kaliuresis, metabolic alkalosis and CT scanning to localize the tumour. Serum aldosterone and plasma renin activity (PRA) were used in addition since 1994. All patients underwent adrenalectomy after adequate preoperative preparation. There was no operative mortality. Postoperatively, normokalaemia was established in all patients. Persistent postoperative hypertension was present in 43.8% of patients.

In our experience, Conn's syndrome could be diagnosed accurately with simple investigations and CT imaging of the adrenal glands. Extensive biochemical testing, including aldosterone and PRA assay, is helpful when the diagnosis is uncertain. While hypokalaemia is curable after surgery, residual hypertension persists in about 45% of patients.