Clinical characteristics of primary aldosteronism: its prevalence and comparative studies on various causes of primary aldosteronism in Yokohama Rosai Hospital.

We studied 1,020 patients with hypertension visiting our outpatient clinic during a five-year period, from 1995 until 1999. Those subjects were screened by determining plasma renin activity (PRA) and plasma aldosterone concentration (PAC) after testing routine laboratory examinations in order to differentiate secondary hypertension from essential hypertension. All patients with low-reninemic hypertension were examined by furosemide plus the upright test. This led to an increase in diagnoses of primary aldosteronism (PA) (confirmed by captopril-loading test). Our studies demonstrated that the incidence of PA is 5.4%, and also that the plasma potassium level is not always beneficial for suspecting the presence of PA, because 28% of the patients with PA show only hypokalemia. We would like to emphasize that adrenal venous sampling plays a critical role in establishing the optimal management for patients with PA, because CT imaging is limited to detection of adrenal masses.