An adrenal incidentaloma is an adrenal mass detected on imaging that was not performed for suspected adrenal disease. The prevalence is approximately 3% and increases up to 10% in older people. The risk of malignancy and a hormone excess have to be evaluated. Approximately 15% of incidentalomas harbor an overproduction of hormones, in particular primary aldosteronism (Conn's syndrome), hypercortisolism (Cushing's syndrome) and pheochromocytoma. Primary aldosteronism is the main cause of endocrine hypertension. It is characterized by an overproduction of aldosterone usually due to a unilateral adenoma or an idiopathic, often bilateral hyperplasia. The aldosterone to renin ratio is an established screening parameter for the diagnosis. If the ratio is elevated a confirmatory test, e. g. saline infusion test, should follow. Usually an adrenal venous catheter has to be used to discriminate between unilateral and bilateral aldosterone overproduction. In the case of unilateral overproduction an adrenalectomy is recommended, otherwise treatment is carried out with an aldosterone antagonist. For the diagnosis of an adrenal Cushing's syndrome a dexamethasone suppression test and a suppressed or in the lower limit of normal ACTH is required. The rare pheochromocytoma is a catecholamine-producing tumor. The diagnosis is carried out by determination of metanephrines in plasma or in 24 h urine samples. Unilateral adrenal tumors leading to clinically significant hormone excess or tumors with suspicion of malignancy should be surgically removed. A minimally invasive adrenalectomy is normally the method of choice in patients with a unilateral adrenal tumor <6 cm and without local tumor invasion. In unilateral, clearly benign, non-functioning, small adrenal tumors (<4 cm) surgery is not required.
Keywords: Conn’s syndrome; Cushing’s syndrome; Hormone activity; Indications for surgery; Pheochromocytoma.