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The adrenal glands are retroperitoneal organs that are primarily involved in the response to stress. They are composed of two distinct layers derived from separate embryologic origins. The outer adrenal cortex (containing the three layers: zona glomerulosa, zona fasciculata, and zona reticularis) is derived from mesoderm and produces steroid hormones involved in the regulation of the stress response, blood pressure, immunometabolic function, and sex hormone steroidogenesis. The inner adrenal medulla is derived from neural crest cells and ectoderm, and it produces the catecholamines, epinephrine and norepinephrine. This architecture of the adrenal gland is the basis for our understanding of surgical adrenal pathology, which generally consists of autonomous hypersecretion of one or more adrenal hormones as well as nonfunctioning benign and malignant tumors.
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ANATOMY & SURGICAL PRINCIPLES
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Each adrenal gland weighs roughly 5 g and measures about 5 cm long and 3 cm wide. The left adrenal gland is situated lateral to the aorta, superior and medial to the kidney, and posterior to Gerota’s fascia. The left adrenal vein is a few centimeters in length and joins with the inferior phrenic vein prior to draining into the left renal vein. The right gland is located superior and medial to the right kidney and posterolateral to the inferior vena cava (IVC). The right adrenal vein is a short and small-diameter vessel that enters directly into the IVC from the posterolateral direction. Importantly, variant venous drainage patterns exist (eg, right hepatic and right adrenal vein communication), and these may be discovered on preoperative imaging. On both sides, the superior, middle, and inferior adrenal arteries consist of small arterial branches from the inferior phrenic arteries, aorta, and renal arteries (Figure 37–1).
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The adrenal cortex consists of three layers. The zona glomerulosa is the most superficial layer and produces mineralocorticoids (eg, aldosterone). The middle layer is the zona fasciculata, which is responsible for glucocorticoid production (eg, cortisol). The zona reticularis is the innermost layer of the adrenal cortex and synthesizes androgens in both males and females (eg, dehydroepiandrosterone [DHEA], androstenedione). The adrenal medulla is the deepest layer within the adrenal gland and regulates the production of catecholamines (eg, epinephrine, norepinephrine). It is innervated by fibers of the autonomic nervous system, which allows for immediate release of catecholamines in response to a stressor.
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Most surgical indications for adrenal pathology relate to hypersecretory states and/or malignancy. A hypersecretory state can result from either autonomous hormone production from the adrenal itself or from upstream trophic hormone overproduction (eg, adrenocorticotropic hormone [ACTH] or renin). A hypersecretory state is confirmed with measurement of adrenal hormones in the blood or urine (eg, aldosterone, cortisol, androgens, or catecholamines). Importantly, the levels of upstream hormones (eg, renin and ACTH) must be concurrently measured as well ...