CHAPTER 19 Adrenalectomy
Case Study
She undergoes laboratory testing, which reveals a serum potassium level of 3.1 mEq/L, a serum renin level of 1.31 ng/mL/hr (normal range, 0.15–3.39 ng/mL/hr), and a serum aldosterone level of 82 ng/dL (normal range, 1–16 ng/dL). A computed tomography (CT) scan of the abdomen shows a 2-cm left adrenal mass and a normal-appearing right adrenal gland (Fig. 19-1).
BACKGROUND
Tumors arising within the adrenal gland are broadly categorized as either functioning or nonfunctioning. The former secrete one of a number of hormones (Table 19-1). The indications for adrenalectomy, the subject of this chapter, include the treatment of functioning adrenal tumors, suspected primary adrenal malignancies, and in select cases, isolated metastases from extra-adrenal malignancies.
INDICATIONS FOR ADRENALECTOMY
I. Aldosteronoma
A. Aldosteronomas are the most common functional adrenal tumor and the most common cause of primary hyperaldosteronism (see Table 19-1). Patients classically present with hypertension refractory to multiple medications and hypokalemia. Other symptoms include headaches, polyuria, nocturia, muscle weakness, and cramping.
B. The presence of a unilateral adrenal lesion with biochemical evidence of primary hyperaldosteronism (see Table 19-1) is an indication for adrenalectomy. When imaging shows either bilateral normal glands or bilateral adrenal nodules, adrenal vein sampling may be used to establish the laterality of the lesion. Patients with lateralizing venous sampling benefit from adrenalectomy. Laparoscopic adrenalectomy is the procedure of choice because these lesions are generally small and benign. In contrast, bilateral aldosterone hypersecretion is managed medically (typically with spironolactone).
II. Cortisol-Producing Adenoma
A. Cortisol overproduction (Cushing’s syndrome) can result from increased adrenocorticotropic hormone (ACTH) production by the pituitary gland (Cushing’s disease) or an ectopic source, or from increased adrenal production of cortisol itself. Cushing’s syndrome may present with central obesity, glucose intolerance, hypertension, excess hair growth, osteoporosis, kidney stones, menstrual irregularity, and emotional lability.
B. The presence of a unilateral adrenal tumor in patients with biochemical evidence of Cushing’s syndrome (see Table 19-1) is an indication for adrenalectomy. Patients with bilateral adrenal hyperplasia and Cushing’s syndrome require bilateral adrenalectomy. Bilateral adrenalectomy is also indicated in patients in whom trans-sphenoidal surgery for Cushing’s disease is unsuccessful and in some patients with ectopic Cushing’s syndrome when the ACTH-secreting tumor cannot be removed.
III. Pheochromocytoma
A. Pheochromocytomas are rare catecholamine-secreting tumors. The symptoms classically associated with these tumors are attributable to excess adrenaline production and include recurrent episodes of sweating, headache, and anxiety. Excessive catecholamine secretion can also precipitate life-threatening hypertension or cardiac arrhythmias.
B. More than 90% of pheochromocytomas are located within the adrenal glands. Extra-adrenal pheochromocytomas, which develop in the paraganglion chromaffin tissue of the sympathetic nervous system, may occur anywhere from the base of the brain to the urinary bladder. Common locations include the organ of Zuckerkandl (at the origin of the inferior mesenteric artery), the bladder wall, the heart, the mediastinum, and the carotid and glomus jugular bodies.
C. The presence of an adrenal tumor with biochemical evidence of a pheochromocytoma (see Table 19-1) is an indication for adrenalectomy. Manipulation of a pheochromocytoma during surgery can result in the release of large amounts of catecholamines and hemodynamic instability. All patients should receive α- and β-antagonists and volume replacement before surgery. α-Blockade must be initiated before β-blockade because hypertensive crises can result from unopposed alpha stimulation.
IV. Adrenocortical Carcinoma
A. Adrenocortical carcinoma is a rare tumor, affecting one to two persons per 1 million. The median age at diagnosis is 44 years. Between 60% and 80% of these tumors are functional. Nonfunctional tumors often present with symptoms related to local invasion or mass effect, such as abdominal or flank pain. Only 30% of these malignancies are confined to the adrenal gland at the time of diagnosis.
B. Cross-sectional imaging (CT scan and magnetic resonance imaging [MRI]) often localizes the tumor. Radiographic findings that suggest malignancy include large size (most adrenal carcinomas are larger than 6 cm at the time of diagnosis), irregular borders, and invasion into surrounding structures. Radical surgical excision, generally performed using an open approach, is the treatment of choice for patients with localized malignancies and remains the only therapy with which long-term disease-free survival can be achieved.
V. Adrenal Metastases. The adrenal glands are relatively common sites of metastases. Breast, lung, and renal cell cancers; melanomas; and lymphomas may metastasize to the adrenal glands. Surgical resection of solitary adrenal metastases in patients with a long previous disease-free interval and no evidence of extra-adrenal disease results in prolonged survival. Imaging, including positron emission tomography scanning to rule out the presence of other metastatic disease and appropriate laboratory testing to determine the functionality of the lesion, should be performed before resection. If pheochromocytoma is ruled out, fine-needle aspiration under CT or ultrasound guidance may also be useful in making a definitive diagnosis.
VI. Incidentalomas. The term incidentaloma refers to an asymptomatic mass or lesion discovered on routine imaging. Adrenal incidentalomas are noted on up to 5% of all abdominal CT scans. In the absence of a history of malignancy, nonfunctioning lesions smaller than 4 to 5 cm are typically followed with serial imaging (CT scan or MRI). Adrenalectomy is usually recommended for nonfunctioning adrenal masses larger than 5 cm because of the elevated risk of malignancy associated with larger lesions. All functioning incidentalomas should be resected (Fig. 19-2).
