الفهرس 
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Abstract
With the increase use of cross-sectional imaging in recent years, the incidentally detected adrenal lesion has become an increasingly common diagnostic problem for the radiologist and a lot of researches along the past decade had tried to find a proper diagnostic approach to classifying these lesions.
Most incidentalomas represent benign disease, typically non-functioning adenoma, still the possibility of malignant disease could not be ignored necessitates a reliance on imaging to inform management decisions.
Seventy percent of adenomas are containing intracytoplasmic fat (lipid rich) and easily identified in non-contrast CT with their low attenuation value ≤ 10 HU and their diagnosis can be confirmed with characteristic DROP of signal seen on opposed phase chemical shift MRI imaging.
Lipid poor adenomas are always described as indeterminate lesions showing mild hyper-attenuated density exceeding 10 HU in non-contrast CT and may also remain indeterminate on MRI imaging and best to be discriminated from other non-adenomatous lesions by their characteristic rapid washout of IV contrast in the delayed phase adrenal dynamic CT protocol with APW > 60% and RPW > 40%.
Non-adenomatous lesion includes large varieties of pathologies including cystic lesions which are easily characterized by CT, adrenal infection and adrenal hemorrhage are commonly represented bilaterally and leaving calcification after their resolving. Also myelolipoma is always represented as large unilateral non-functioning mass lesion with macroscopic fat content which is easily discriminated by either CT or MRI imaging.
Both pheochromocytoma and metastasis may result in a large, heterogeneous adrenal mass; however, correlation with medical history, laboratory and imaging finding may favor one diagnosis than the other; as adrenal metastasis mostly presented bilaterally in patient with primary extra-adrenal malignancy, while pheochromocytoma is mostly represented as unilateral lesion in non syndromic cases with characteristic biochemical activity and clinical finding. CT and MRI imaging features of both lesions could be identical as both can show slow washout of IV contrast in delayed phase of dynamic CT protocol, no DROP of signal seen in chemical shift sequence, both can show heterogeneous enhancement in post IV contrast administration and restricted diffusion on DWI, however more percentage of pheochromocytoma are tend to give hyperintense signal on T2-wieghted images (light bulb sign) in about 70% of cases.
Adrenocortical carcinomas are rare and majority of cases are metastatic at the time of diagnosis, with the most common sites of spread being the local peri-adrenal tissue, lymph nodes, lungs, liver, and bone. They tend to be demonstrated as large partially necrotic inhomogeneous mass > 6 cm in size with heterogeneous pattern of enhancement and type III enhancement curve in dynamic post contrast MRI study.
Other adrenal lesions are considered as rarities with no specific imaging characteristic features and always need histopathological tissue biopsy diagnosis.