Adrenal Lesions: Spectrum of Imaging Findings with Emphasis on Multi-Detector Computed Tomography and Magnetic Resonance Imaging

Abstract

The adrenal gland is a common site of a large spectrum of abnormalities like primary tumors, hemorrhage, metastases, and enlargement of the gland from external hormonal stimulation. Most of these lesions represent nonfunctioning adrenal adenomas and thus warrant a conservative management. Multi-detector computed tomography (CT) and magnetic resonance (MR) imaging are still considered highly specific and complementary techniques for the detection and characterization of adrenal abnormalities. Radiologist can establish a definitive diagnosis for most adrenal masses (i.e., carcinoma, hemorrhage) based on imaging alone. Imaging therefore can differentiate malignant lesions from those benign and avoid unnecessary aggressive management of benign lesions. The article gives an overview of the adrenal lesions and their imaging characteristics seen on CT and MR imaging.

Bilateral adrenal haemorrhages: a crucial incidental finding

“…There is a gradual reduction in adrenal size over time and there may be evidence of calcification. 3 , 11 In this patient, the acute enlargement of adrenal glands, HU > 10, and a subsequent follow-up scan revealing a reduction in size are most consistent with a diagnosis of haemorrhage.…”

Radiological and Pathological Findings in a Case of Large Left Adrenal Myelolipoma

“…Cross-sectional imaging readily characterizes benign adrenal masses such as lipid rich adenomas, myelolipomas, adrenal cysts and adrenal hemorrhage as they have characteristic diagnostic imaging features that show the presence of lipid, intralesional fat, water, or blood [4].…”

Pitfalls and differential diagnosis on adrenal lesions: current concepts in CT/MR imaging: a narrative review

“…When an adrenal mass is found incidentally on imaging, a dedicated CT protocol is usually performed to evaluate the mass. The overlapping venous phase enhancement patterns of adenomas and non-adenomas requires a delayed image series executed 10-15 minutes after contrast medium injection to establish if the lesion shows washout or not (31,32). The absolute percentage washout (APW) and relative percentage washout (RPW) can be obtained through a set formula (29,31,33).…”

“…Various MR imaging parameters can be used in order to characterize adrenal masses, but the most useful is represented by the Chemical Shift Imaging (CSI) which allows the detection of intracellular lipid that is contained in most frequent adrenal lesions (adenomas) with loss of signal in the "out of phase" sequence (OP) (33)(34)(35). The loss of signal intensity can be demonstrated also with a quantitative analysis through specific formula based on the adrenal-to-spleen chemical shift ratio (ASR) or the adrenal sensitivity index (SII) (31,36,37) avoiding liver and the muscle because of the frequent presence of fat content that may also cause signal loss on the OP sequences (31). 3T MRI system with the assessment of new sequences could allow to distinguish adenomas from non-adenoma but it has not contributed more than to the use of CSI (31,38).…”

“…The loss of signal intensity can be demonstrated also with a quantitative analysis through specific formula based on the adrenal-to-spleen chemical shift ratio (ASR) or the adrenal sensitivity index (SII) (31,36,37) avoiding liver and the muscle because of the frequent presence of fat content that may also cause signal loss on the OP sequences (31). 3T MRI system with the assessment of new sequences could allow to distinguish adenomas from non-adenoma but it has not contributed more than to the use of CSI (31,38). MRI could be particularly useful to study adrenal lesions with an unenhanced CT attenuation between 10 and 30 HU, while contrast-enhanced CT might be more useful for analysing nodules with attenuation values greater than 30 HU (39).…”