Adrenal Venous Sampling for Assessment of Autonomous Cortisol Secretion.

Context: Autonomous cortisol secretion (ACS) can be unilateral or bilateral irrespective of the presence of an adrenal tumor. A reliable method to distinguish between unilateral and bilateral ACS is lacking.
Objective: Evaluate the use of adrenal venous sampling (AVS) to distinguish between unilateral and bilateral ACS.
Design and Methods: This was a prospective study of AVS in patients with adrenal tumors who received a diagnosis of ACS or adrenal Cushing syndrome (CS). Unilateral secretion was defined as >2.3-fold difference in cortisol levels between the two adrenal veins. Metanephrine levels were used to ascertain correct catheter position. Results were correlated with findings on CT and iodine-131-cholesterol scintigraphy.
Results: Thirty-nine patients underwent AVS; there were no complications. The procedure was inconclusive in six patients and repeated with success in one, giving a success rate of 85%, and leaving 34 procedures for evaluation (adrenal CS, n = 2; ACS, n = 32). Of 14 patients with bilateral tumors, 10 had bilateral and 4 had unilateral overproduction. Of 20 patients with unilateral tumors, 11 had lateralization to the side of the tumor and the remaining had bilateral secretion. Cholesterol scintigraphy findings were concordant with those of AVS in 13 of 18 cases (72%) and discordant in 5 (28%).
Conclusion: Laterality of ACS does not always correspond to findings on CT images. AVS is a safe and valuable tool for differentiation between unilateral and bilateral cortisol secretion and should be considered when operative treatment of ACS is a possibility.