Computed tomography is the first line modality in the evaluation of patients with adrenal gland masses, and has the potential to be very accurate in the localization of adrenal gland masses in patients with diseases associated with hyperfunctioning conditions of the adrenal gland. Computed tomography allows a specific diagnosis of acute adrenal haemorrhage, adrenal myelolipoma, and adrenal cysts. It is also helpful in the assessment of patients with Addison's disease, particularly the subacute form secondary to granulomatous diseases. Quantitative evaluation of adrenal masses on unenhanced or delayedenhanced computed tomography has been shown to be highly accurate in distinguishing adrenal adenomas from nonadenomas. Attenuation of 18 HU or less on unenhanced computed tomography scans indicates adenoma with a high specificity and acceptable sensitivity. On delayedenhanced computed tomography scans, adrenal adenomas exhibit a greater washout of contrast material than do adrenal nonadenomas. Therefore, adrenal nonadenomas have significantly higher attenuation than adenomas on delayedenhanced computed tomography scans obtained at arbitrarily chosen times (3-60 min) after the initiation of contrast material administration.
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