Predicting surgically remedial primary aldosteronism: role of adrenal scanning,posture testing,and adrenal vein sampling

Distinguishing surgically remedial forms from other causes of primary aldosteronism (PA) may be difficult, and it is made more challenging by the earlier detection of milder disease. The technical demands of bilateral adrenal vein sampling (AVS)-increasingly advocated for localizing a unilateral autonomous lesion (UAL)- and lack of agreed criteria for establishing unilateral autonomy, add further to the diagnostic challenge. This retrospective review of 49 hypokalemic patients with unequivocal PA (41 with surgically proven and remedial UAL, eight patients with bilateral adrenal hyperplasia) analyzes the value of computerized tomography adrenal scanning (n = 32), 4 h erect posture testing (n = 42), and AVS (n = 27) in predicting and lateralizing a surgically remedial lesion. A fall in plasma aldosterone during 4 h erect posture (positive test) occurred in 63% of patients with UAL and in none with bilateral adrenal hyperplasia. A positive posture test or computerized tomography adrenal scan (single focal macroadenoma) both had high positive predictive value (100% and 89% respectively), but low sensitivity for diagnosis of UAL. AVS, undertaken during low dose ACTH stimulation, localized the UAL in all cases (positive predictive value 100%) where the aldosterone/cortisol ratio of blood drawn from the uninvolved gland was less than that of peripheral blood (contralateral ratio <1). Biochemical severity, reflected by overnight supine plasma aldosterone, was strongly correlated with the degree of contralateral gland suppression (n = 16, r = 0.79, P < 0.001). Importantly, the AVS findings show that when bilateral access is not possible, UAL can be successfully lateralized when only one adrenal vein (the contralateral) is accessed, or the ipsilateral vein is sampled in subjects whose posture test was positive. In this series of patients with overt (hypokalemic) PA, preoperative testing successfully identified a surgically remedial lesion in 39 of 41 cases. Confirmation of the recommended diagnostic approach must now await larger prospective studies.