CONCEPTUAL BASIS AND DIAGNOSIS OF PRIMARY ALDOSTERONISM

Primary aldosteronism comprises two different conditions, the tumoral form usually caused by an adenoma and the idiopathic form due to nodul ar hyperplasia of the two adenals. More rarely, an adenoma of the adre nal cortex, glucocorticosteroid-sensitive hyperplasia, and angiotensin -sensitive adenoma or an autonomous nodule transformed to primary tumo ral hyperplasia, may be observed. Primary alderosteronism may be conce ived as a spectrum of genetic abnormalities which express themselves e ither by hyperplasia or by a tumour. A defect in steroid genesis and p rolonged stimulation of the cortex would lead to the formation of nodu les which may become autonomous and generate a tumour. Hypertension ma y be isolated. Detection requires three sampling of serum potassium in all hypertensive patients, a study of the aldosterone-renin axis when the value is less than 3.6 mEq, or whenever the hypertension is sever e or resistant to treatment. The diagnosis is made by the association of an increased plasma aldosterone level before getting up in the morn ing and a plasma renin unaffected by orthostatism. The choice of medic al or surgical treatment depends on the uni- or bilateral anatomic sub strate. Computerised tomography, very sensitive but not specific, like hormonal studies, often provides incomplete answers. Adrenalectomy is indicated in the presence of a mass of centimetric proportions with c oncordant results of the dynamic test. In other situations, investigat ions are continued with the search for an aldosterone gradient by sele ctive venous sampling. This is very valuable to determine the laterali sation but fails in 25 % of cases, and its results have to be compared with those of imaging techniques: CT scan, venography and, when neces sary, scintigraphy. However, when all investigations have been complet ed, it is not always possible to reach a definitive conclusion. In non -surgical patients, in the absence of anatomical proof, the diagnosis remains presumptive. Progress is awaited in the detection of normokali emic forms and in the identification of surgically suitable cases whic h are certainly underestimated,