RELATIVE VALUE OF COMPUTED-TOMOGRAPHY SCANNING AND VENOUS SAMPLING INESTABLISHING THE CAUSE OF PRIMARY HYPERALDOSTERONISM

The purpose of this study was to evaluate the relative merits of the p ostural stimulation test, adrenal computed tomography (CT) and venous sampling in the differential diagnosis of patients presenting with pri mary hyperaldosteronism. The records of 20 patients presenting with pr imary hyperaldosteronism were reviewed retrospectively. There were 15 patients with a unilateral aldosterone-producing adenoma (APA), four p atients with idiopathic hyperaldosteronism (IHA) and one patient with primary adrenal hyperplasia (PAH). The postural stimulation lest was b ased on measurements of plasma aldosterone and renin activity at 08.00 h and at noon after 4 h of ambulation. The CT scans of the adrenals w ere reviewed by a single radiologist. Bilateral venous sampling of adr enal veins was attempted in all patients and blood collected for aldos terone and cortisol assay. Plasma aldosterone concentration increased after 4 h of standing in all cases of hyperplasia but was also demonst rated in 10/15 patients with a surgically-proven APA. If one defines a significant postural rise as being greater than 30%, then 8/15 patien ts with APA can be considered as being posturally responsive. Computed tomography scanning correctly identified all 15 cases of APA and also classified correctly the remaining live cases of hyperplasia (four ca ses of IHA and one case of PAH). Venous sampling failed technically in 4/15 cases of APA and in one case of IHA: a total of 5/20 (25%). A co rrect diagnosis of APA or IHA was established in all the remaining cas es. However, the one case of PAH was treated successfully by adrenalec tomy following venous sampling, which suggested a unilateral adrenal l esion: this one result was the only instance where venous sampling alt ered clinical decision-making. Computed tomography scanning may be use d alone to confirm the cause of hyperaldosteronism where postural stud ies suggest an adrenal adenoma, and such patients may be considered fo r early surgery. Venous catheterization studies are not necessary rout inely, but may still be useful in selected patients, particularly when CT scanning shows no clear lesion.