Objective  To investigate the diagnostic value of adrenal vein sampling (AVS) in adrenocorticotropic hormone (ACTH)-independent Cushing's syndrome with bilateral adrenal masses.

  Methods  A retrospective analysis of 4 cases of ACTH-independent Cushing's syndrome with bilateral adrenal masses treated in Peking Union Medical College Hospital was performed. Bilateral adrenal venous blood and peripheral venous blood samples were collected under fasting state for measurement of cortisol and aldosterone concentrations. The ratio of cortisol level in adrenal venous blood to that in peripheral venous blood was calculated, as well as the cortisol-to-aldosterone ratios in bilateral adrenal veins.

  Results  Based on the results of AVS, the average odds ratio of bilateral cortisol/aldosterone of the 4 cases was 8.4 (3.6-16.2). Among these patients, 3 cases were diagnosedas overt Cushing's syndrome caused by unilateral cortisol-secreting hyperfunctioning adrenal adenoma with contralateral nonfunctioning cortical adenoma; the other case was subclinical Cushing's syndrome caused by unilateral cortisol-secreting hyperfunctioning adrenal adenoma with contralateral nodular adrenal hyperplasia. After unilateral adrenalectomy guided by localization diagnosis, all of these 4 patients had complete remission. During a mean follow-up of 36 months, Cushing's syndrome or clinically important cortisol secretory autonomy did not recur.

  Conclusions  AVS can contribute to measure the adrenal function in ACTH-independent Cushing's syndrome with bilateral adrenal masses, and is of important value to guide the decision on treatment. The key factors for successful AVS are catheterization into the adrenal vein and exclusion of endogenous interference factors.