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1660. Performance Characteristics of CT Washout in Lipid Poor Adrenal Incidentalomas
Authors * Denotes Presenting Author
  1. Erick Remer *; Cleveland Clinic
  2. Serkan Akbulut; Cleveland Clinic
  3. Ozgun Erten; Cleveland Clinic
  4. Mehmet Gokceimam; Cleveland Clinic
  5. Eren Berber; Cleveland Clinic
Objective:
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.

Results:
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.

Conclusion:
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.