1660. Performance Characteristics of CT Washout in Lipid Poor Adrenal Incidentalomas
Authors* Denotes Presenting Author
Erick Remer *;
To assess the performance of CT wash out for lipid poor adenomas in a population of adrenal incidentalomas and to compare results to earlier series of adenomas and nonadenomas that were comprised of primarily metastases
Materials and Methods:
We identified patients with lipid poor adrenal incidentalomas who had washout CT in a single institution in IRB-approved database from 2003-2019 and tabulated lesion size, attenuation, washout, pathology, and used descriptive statistics and Mann-Whitney test.
156 patients with 175 lesions were identified with mean size 3.0±0.2 cm (range 1.1-16.3). Reference standard was adrenalectomy 70(40%), percutaneous biopsy 4 (2.3%), and follow-up 101 (57.7%) [median= 4 years (range 1-15)]. Absolute washout was =60% in 102 lesions (58.3%); 93 (91.3%) were adenomas, 7 (6.9%) pheochromocytomas, 1 (0.9%) myelolipoma, and 1 (0.9%) adrenal hematoma. Absolute washout <60% in 73 lesions (41.7%); 45 (61.6%) adenomas, 8 (11%) pheochromocytomas, 9 (12.3%) metastases, 6 (8.2%) adrenocortical cancer and others in 5 (6.9%). For detecting adenoma, the sensitivity was 67.4%, specificity was 75.7%, PPV was 91.2%, was NPV 38.4%, and accuracy was 69.1%. This compares to a previously reported sensitivity of 86–88% and specificity of 92–96%. If pheochromocytomas were excluded, specificity was 90.9% and PPV 97.9%. Unenhanced attenuation (p=0.016) and washout % (p=0.033) were significantly different between adenomas and pheochromocytomas.
CT washout performance is less robust in the incidentaloma population than that in which it was originally described. Performance degradation is likely attributable to washout in unrecognized pheochromocytomas.