Adrenal Cortical Nodular Hyperplasia

The adrenal glands are paired retroperitoneal structures located superior to the kidneys. Adrenal glands are divided into 2 physiologically separated segments: the cortex and the medulla. The cortex has 3 distinct layers: the zona glomerulosa, which secretes mineralocorticoids; the zona fasciculata, which secretes glucocorticoids; and the zona reticularis, which secretes androgens. The adrenal medulla secretes epinephrine and norepinephrine in response to dopamine, which is secreted during stress reactions. Cortical hyperplasia is the enlargement of the adrenal cortex, usually due to functional or, more commonly, nonfunctional nodules. Adrenal tumors are very common and often discovered incidentally on imaging for unrelated issues. Present in up to 4% of the general population, the incidence increases with age, in those with diabetes, hypertension, or who are obese. Increased detection of cortical enlargement is also due to imaging technology advances and increased frequency of imaging studies. For example, in the United States and Canada, between 2000 and 2016, the number of magnetic resonance imaging and computed tomography studies performed doubled and, in some cases, even tripled.  Incidentally found lesions are often called "incidentalomas" due to the benign nature of most lesions. However, there are some exceptions, notably functional adrenal lesions (usually secreting cortisol) comprising fewer than 10% of the total lesions and adrenocortical carcinoma comprising fewer than 2% of all cases—but with metastatic potential. In addition, the adrenal gland is highly vascularized, despite its small size, and therefore is at risk for metastatic disease. The most common primary malignancies metastatic to the adrenal gland are lung (about 35%), gastrointestinal, kidney, and breast. Bilateral nodules are more common with metastatic disease than other etiologies, so this finding should raise concern for metastatic disease.