Diseases of the Abdomen and Pelvis 2023-2026 by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783031273551
Publisher: Springer International Publishing

There are two features of adenomas that are helpful in their characterization on CT and MRI: (1) the presence of intracellular lipid—low density on unenhanced CT, and loss of signal intensity and chemical shift (CSI) out-of-phase (OOP) MRI and (2) CT contrast washout features—rapid washout on contrast-enhanced CT.

10.2.1 Unenhanced CT

Most incidental adenomas are lipid-rich adenomas (measuring ≤10 HU on unenhanced CT) although between 20%–30%, are lipid-poor adenomas measuring >10 HU [6, 7]. Unenhanced CT density measurement of ≤10HU is highly specific (>95%) for the diagnosis of adenoma; however, some studies have shown that even higher density numbers could be used to diagnose benign adrenal lesions [8, 9]. In a recent study of 250 patients with incidental adrenal masses, who either underwent surgery or follow-up for at least 1 year, it was shown that even if the density threshold on unenhanced CT was raised to <20 HU for lesions <3 cm, and <15 HU for lesions <4 cm, a specificity of 100% for predicting benign lesions could be achieved [8]. However, this threshold, currently lacks sufficient evidence for routine clinical use.

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