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The adrenal, or suprarenal, glands are paired retroperitoneal organs positioned superomedial to the kidneys at the level of the 12th rib. Each gland is divided into an outer cortex and an inner medulla, which are histologically and functionally distinct layers derived from separate embryologic tissues. The cortex originates from ectoderm and is composed of three zones that produce steroid hormones: the zona fasciculata, which produces mineralocorticoids; the zona glomerulosa, which produces glucocorticoids; and the zona reticularis, which produces sex hormones. The medulla is derived from neural crest cells and is composed of modified postganglionic neurons that connect with the sympathetic nervous system in order to produce epinephrine, norepinephrine, and dopamine in response to sympathetic stimuli.
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The arterial supply to the adrenals originates from the inferior phrenic arteries, aorta, and renal arteries. Although the anatomy is quite variable, the majority of the arterial supply approaches from the medial and inferior borders of the adrenal glands with few substantial arteries from the superior, posterior, or lateral sides. The adrenal arteries are generally small and amenable to electrocautery. Conversely, the venous anatomy to the adrenal gland is more consistent; usually there is a single large draining vein of substantial size that requires ligation. The right adrenal vein length tends to be short and it drains directly into the inferior vena cava (IVC). In contrast, the left adrenal vein is usually of generous length and drains into either the left renal vein or the inferior phrenic vein. Ligation of the left inferior phrenic vein is of no significant physiologic consequence. The adrenal gland is surrounded by variable amounts of fat, which is loosely attached posteriorly to diaphragmatic muscle. This surrounding fat can obscure the visualization and identification of adrenal tumors. Left-sided adrenal tumors can be adjacent to the spleen, pancreas tail, liver, kidney, or renal hilum. Right-sided adrenal tumors can be adjacent to the liver or IVC. Invasive adrenal tumors can extend into these surrounding structures.
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Aldosteronomas are cortical adrenal tumors that autonomously secrete aldosterone. Hyperaldosteronism was first described by Jerome Conn in 1955 and is characterized by hypertension and hypokalemia.1 These symptoms should be controlled preoperatively with an aldosterone antagonist and potassium supplements. Biochemical confirmation of autonomous hypersecretion of aldosterone should be confirmed prior to adrenalectomy. This is best achieved by salt loading followed by a 24-hour urine collection of aldosterone, sodium, and creatinine. Aldosterone antagonists should be held prior to testing for at least a few weeks. While there are several forms of primary hyperaldosteronism, surgery is indicated only in the setting of unilateral adrenal adenoma or hyperplasia. Because aldosteronomas are almost always benign tumors, a cortex-sparing nodulectomy can be performed when the tumor is peripheral; however, this approach has a higher risk of persistent hyperaldosteronism.
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Since benign, nonfunctional adrenal tumors are common relative to the incidence of hyperaldosteronism, selective venous sampling should be used to confirm laterality of disease in ...