Discriminative capacity of volumetry by CT scan to identify autonomous cortisol secretion in incidental adrenal adenomas

Context Incidentally discovered adrenal adenomas are common. Assessment for possible autonomous cortisol excess (ACS) is warranted for all adrenal adenomas given the association with increased cardiometabolic disease. Objective To evaluate the discriminatory capacity of three-dimensional volumetry on computed tomography (CT) to identify ACS. Design, Setting, Patients Two radiologists, blinded to hormonal levels, prospectively analyzed CT images on 149 adult patients with unilateral, incidentally-discovered, adrenal adenomas. Main Outcome Measures Diameter and volumetry of the adenoma, volumetry of the contralateral adrenal gland, and the adenoma volume-to-contralateral gland volume (AV/CV) ratio were measured. ACS was defined as cortisol≥1.8 mcg/dL after 1mg dexamethasone suppression test (DST) and a morning ACTH ≤15 pg/mL. Results We observed that ACS was diagnosed in 35 (23.4%) patients. Cortisol post-DST was positively correlated with adenoma diameter and volume, and inversely correlated with contralateral adrenal gland volume. Cortisol post-DST was positively correlated with the AV/CV ratio (r=0.46, p<0.001) and ACTH was inversely correlated (r=-0.28, p<0.001). The AV/CV ratio displayed the highest Odds Ratio (1.40 CI 95% 1.18-1.65) and area under curve (0.91 CI 95% 0.86-0.96) for predicting ACS. An AV/CV ratio ≥1 (48% of the cohort) had a sensitivity of 97% and a specificity of 70% to identify ACS. Conclusions CT volumetry of adrenal adenomas and contralateral adrenal glands has a high discriminatory capacity to identify ACS. The combination of this simple and low-cost radiological phenotyping can supplement biochemical testing to substantially improve the identification of ACS.