Incidental Adrenal Nodules11

GENERAL PRINCIPLES

• Adrenal nodules are a common incidental finding on abdominal imaging studies.

• Most incidentally discovered nodules are benign adrenocortical tumors that do not secrete excess hormone.

DIAGNOSIS

Clinical Presentation

Patients should be evaluated for hypertension, symptoms suggestive of pheochromocytoma (episodic headache, palpitations, and sweating), and signs of Cushing syndrome (see “Cushing Syndrome” section).

Differential Diagnosis

• In patients without a known malignancy elsewhere, the diagnostic issues are whether a syndrome of hormone excess or an adrenocortical carcinoma is present.

• The differential diagnosis includes adrenal adenomas causing Cushing syndrome or primary hyperaldosteronism, pheochromocytoma, adrenocortical carcinoma, and metastatic cancer.

• The imaging characteristics of the nodule may suggest a diagnosis but are not specific enough to obviate further evaluation.

Diagnostic Testing

• Plasma potassium, metanephrines, and dehydroepiandrosterone sulfate should be measured, and an overnight dexamethasone suppression test should be performed.

• Patients who have potentially resectable cancer elsewhere and in whom an adrenal metastasis must be excluded may require fluorodeoxyglucose-positron emission tomography.

• Patients with hypertension (especially if they have hypokalemia) should be evaluated for primary hyperaldosteronism by measuring the ratio of plasma aldosterone (in nanograms per deciliter [ng/dL]) to plasma renin activity (in ng/mL/h). If the ratio is lt;20, the diagnosis of primary hyperaldosteronism is excluded, whereas a ratio gt;50 makes the diagnosis very likely. Patients with an intermediate ratio should be further evaluated in consultation with an endocrinologist.

• An abnormal overnight dexamethasone suppression test should be evaluated further (see “Cushing Syndrome” section).

• Elevation of plasma dehydroepiandrosterone sulfate or a large nodule (gt;4 cm in diameter) suggests adrenocortical carcinoma.

TREATMENT

• Most incidental nodules are lt;4 cm in diameter, do not produce excess hormone, and do not require therapy. A measurement of lt;10 Hounsfield units on CT is reassuring for adrenal adenoma. One repeat imaging procedure 3-6 months later is recommended to ensure that the nodule is not enlarging rapidly (which would suggest an adrenal carcinoma).

• A policy of resecting all nodules gt;4 cm in diameter appropriately treats the great majority of adrenal carcinomas while minimizing the number of benign nodules that are removed unnecessarily.

• If clinical or biochemical evidence of a pheochromocytoma is found, the nodule should be resected after appropriate #945;-adrenergic blockade.