CT of hemorrhagic adrenal adenomas: radiologic-pathologic correlation

To describe the appearance of chronically hemorrhagic adenomas on adrenal protocol CT and correlate imaging with pathologic findings.

Retrospective case series of adult patients with resected adrenal adenomas showing internal hemorrhage at histology. Seven of nine patients underwent pre-operative adrenal protocol CT and 2/7 underwent unenhanced CT with portal venous phase CT. Two abdominal radiologists in consensus assessed the CT images for the presence of calcifications, macroscopic fat, cystic/necrotic appearance, and the presence, pattern, and percent nodule volume of areas < 10 HU on unenhanced CT. Absolute washout was calculated using a large ROI, and ROIs on the highest and lowest attenuating regions on the portal venous phase.

Mean adenoma length was 4.9 cm. All adenomas had areas measuring < 10 HU on unenhanced CT, ranging from < 20 to > 80% nodule volume. Calcifications were present in 4/9 adenomas and gross fat in 4/9 on CT. Of the seven cases with adrenal protocol CT, the absolute washout was < 60% in 5/7 using the large ROI, 5/7 using the low attenuation ROI, and 7/7 using the high attenuation ROI. At histology, all nine cases had microscopic evidence of hemorrhage, lipid rich adenoma cells, and fibrosclerosis. Myelolipomatous changes were identified in 4/9 cases, with the remaining five cases showing lipomatous metaplasia without a myeloid component.

Chronically hemorrhagic adrenal adenomas demonstrated variable areas < 10 HU on unenhanced CT corresponding to lipid rich adenoma cells. Absolute washout was most often < 60%, hypothesized to be due to fibrosclerosis within the adenomas.