A case of aldosterone-producing adenoma diagnosed by adrenal arteriography and branch selective adrenal venous sampling

Case report: A 43-year-old man had been followed up for hypertension and hypokalemia, but self-interrupted his hospital visits for the last four years. Based on the serum potassium level of 2.7 mEq/L, plasma aldosterone concentration of 202 pg/mL, and plasma renin activity of 1.1 ng/mL/hr, he was suspected of primary aldosteronism and was admitted to the previous hospital. A saline suppression test and a rapid ACTH stimulation test were both positive, and 24-hr urinary aldosterone level was 19 μg/day under sodium loading of 170 mEq/day, leading to the diagnosis of primary aldosteronism. Since contrast-enhanced CT showed an 8 mm-sized adenoma in the lower portion of the left adrenal gland, an aldosterone-producing adenoma was suspected and a non-segmental adrenal venous sampling (AVS) was performed. However, it yielded apparent bilateral aldosterone suppression in the main trunk of the bilateral adrenal veins, where the aldosterone-to-cortisol (A/C) ratio was lower than that in the inferior vena cava even after ACTH loading. The patient was referred to our hospital for a segmental AVS. Arteriography was first performed from the left inferior adrenal artery to confirm the outflow vessels from the adenoma. Strikingly, there was an aberrant vein which drained into the proximal segment of the left adrenal vein. CT imaging at the time of arteriography revealed, in addition to the known adenoma, a 6 mm-sized micronodule in the lateral region of the left adrenal gland, and the aberrant vein appeared to be the main outflow vessel from the micronodule. A segmental AVS was performed, and blood samples were taken from the bilateral adrenal veins including the aberrant vein and the main trunk of the left adrenal vein proximal to its confluence. The A/C ratio was highest in the aberrant vein, followed by in the main trunk of the proximal left adrenal vein, while it was markedly suppressed in other branches and the main trunk of the left adrenal vein distal to the confluence of the aberrant vein. Based on these results, the presence of aldosterone-producing adenoma in the left adrenal gland was suggested. Laparoscopic partial left adrenalectomy was performed without postoperative complications. Hypertension and hypokalemia were fully resolved afterwards. Conclusions: Adrenal arteriography and segmental AVS should be considered in such cases that apparent bilateral aldosterone suppression is noted in conventional AVS in patients with clinically suspected aldosterone-producing adenoma.