Imaging description

Minor adrenal nodularity or thickening is a common finding at CT or MRI [1], and represents a diagnostic problem that is distinct from and commoner than the more well-described dilemma of an incidental adrenal mass [1,2]. Smooth enlargement has been defined as diffuse thickening of the adrenal glands with a limb thickness of over 6 to 8 mm (Figure 35.1) [3], while nodularity has been defined as multifocal surface irregularity without a unifocal or dominant nodule over 1 cm in diameter or unifocal surface irregularity under 1 cm in diameter (Figure 35.2) [4].

Importance

Minor adrenal nodularity or thickening is most problematic when seen in a patient with a known primary malignancy, because of the concern that such abnormalities are an early sign of metastases. This concern is particularly acute in patients with primary lung cancer, where the frequency of metastases to the adrenal glands at autopsy may be as high as 35% [5].

Typical clinical scenario

Minor morphologic abnormalities of the adrenal glands are common. For example, in one series of 197 patients with lung cancer, two independent readers reported smooth enlargement in 11 to 18% of adrenal glands and minor nodularity in 18 to 23% [4].

Differential diagnosis

In a study of 197 patients with lung cancer and no obvious adrenal metastases at baseline CT [4], adrenal metastases subsequently developed over a mean follow-up period of 1.3 years in 13 adrenal glands of 11 patients.