Editing Diagnosis and Evaluation of Adrenal Mass (section)

=== Imaging ===

==== CT ====
* '''<span style="color:#ff0000">Unenhanced CT scan is the first test</span>'''
** '''Myelolipoma, cysts and hemorrhages have distinct features on imaging'''
**'''Most easily interpreted test for intracellular lipid'''
*** '''<span style="color:#ff0000">Adenomas typically contain a greater proportion of intracellular fat</span>''' in comparison to malignant incidentalomas.
** '''<span style="color:#ff0000">If attenuation of a region of interest over a mass on unenhanced CT</span>'''
***'''<span style="color:#ff0000"><10 HU, diagnostic for an adrenal adenoma (corresponds to high intracytoplasmic lipid content)</span>'''
**** '''<span style="color:#ff0000">This cutoff has ≈70% sensitivity and 98% specificity for the diagnosis of adrenal adenomas</span>'''
***** '''<span style="color:#ff0000">≈30% of adrenal adenomas exhibit an attenuation >10 HU on unenhanced CT owing to their lower lipid content</span>'''
****** '''These “atypical adenomas” or "lipid-poor adenomas" are indistinguishable from non-adenomas on non-contrast CT density measurements alone'''
*** '''<span style="color:#ff0000">>10 HU, obtain contrast enhanced CT with washout</span>'''
**** Contrast enhanced CT with washout has excellent sensitivity and specificity in differentiating between adenomas and non-adenomatous incidentalomas
*****The diagnostic information from a single-phase enhanced CT scan for adrenal lesions is quite limited, as there is considerable overlap in post-contrast attenuation of adenomas and non-adenomas
**** '''Phases of adrenal CT study (3):'''
****# '''Non-contrast 5-mm images through the adrenal'''
****# '''Enhanced (1-minute post-bolus imaging)'''
****# '''15-minute washout imaging'''
**** '''<span style="color:#ff0000">Delayed (washout) imaging indicative of adrenal adenoma</span>'''
***** '''<span style="color:#ff0000">Absolute percent washout > 60%</span>''' ([Enhanced − delayed]/[Enhanced − unenhanced] × 100%)
***** '''<span style="color:#ff0000">Relative percent washout (RPW) > 40%</span>''' ([Enhanced − delayed]/ [Enhanced] × 100%)
****** '''Lipid-poor adenomas possess identical properties to lipid-rich adenomas regarding their rapid loss (washout) of enhancement after CT contrast'''
****** RCC metastases and HCC mets may exhibit washout characteristics similar to those of lipid-poor adenomas
* '''<span style="color:#ff0000">Characteristics of pheochromocytoma and malignant processes include (5):</span>'''
*# '''<span style="color:#ff0000">Size (>3 cm)</span>'''
*# '''<span style="color:#ff0000">Heterogenous texture</span>'''
*# '''<span style="color:#ff0000">Increased vascularity</span>'''
*# '''<span style="color:#ff0000">Attenuation of >10 HU on unenhanced CT</span>'''
*# '''<span style="color:#ff0000">Decreased contrast washout''' at 10 to 15 minutes</span>

==== MRI ====
* '''Similar to CT scan, chemical-shift MRI uses the lipid-rich property of most adenomas to differentiate benign from malignant'''
* '''CT with washout is considered the gold standard and is better than chemical shift MRI for identifying adenomas'''

==== Ultrasound ====
* '''Suboptimal imaging modality for detecting and characterizing adrenal lesions'''

==== Functional imaging ====
* '''The role of functional imaging for the diagnosis of pheochromocytoma is limited, given that most pheochromocytomas can be accurately diagnosed with cross-sectional imaging and metabolic evaluation for catecholamines and their metabolites.'''

==== PET ====
* '''2-[18F] FDG-PET scan can be useful in detecting metastasis in patients with a history of malignancy''', as metabolically-active lesions typically have increased uptake of FDG versus benign lesions.