Ueland GA, et al. - In this prospective study, researchers assessed the use of adrenal venous sampling (AVS) to distinguish between unilateral and bilateral autonomous cortisol secretion (ACS). The study sample consisted of AVS in patients with adrenal tumors who received a diagnosis of ACS or adrenal Cushing syndrome (CS). To ascertain correct catheter position, metanephrine levels were used. ACS laterality does not always match CT image findings. The findings suggested that AVS is a safe and valuable tool for differentiating unilateral and bilateral cortisol secretion and should be considered when there is a possibility of ACS operative treatment.