Aldosteronism atau Conn’s syndrome

Clinical
Primary aldosteronism (Conn’s syndrome) is secondary to either an aldosterone-secreting neoplasm or adrenal hyperplasia. Over half of
primary aldosteronism is due to a functioning adrenocorticoid adenoma (aldosteronoma). Hyperplasia, usually bilateral, accounts for most of the rest, with a carcinoma being rare. Bilateral adenomas have been reported. Some patients with Conn’s syndrome have grossly normal-appearing glands. A pheochromocytoma and primary hyperaldosteronism have occurred simultaneously; whether this is a coincidence or an unknown interreaction is conjecture.
The mineralocorticoid aldosterone is involved in blood volume and serum potassium homeostasis,which in turn regulate aldosterone secretion by the zona glomerulosa in the adrenal cortex. Excessive secretion leads to  hypertension, hypokalemia, and suppression of plasma renin activity, a condition also known as
mineralocorticoid hypertension. This is not a simple condition; although in most patients the two stimuli for aldosterone production (potassium and angiotensin II) tend to be low, some patients have normal serum potassium levels. Familial hyperaldosteronism is described. A curious sideshow is pseudohypermineralocorticism, caused by an excess of mineralotropics other than aldosterone.
Although mineralocorticoid hypertension is not common, its significance lies in its being a potentially correctable cause of high blood pressure. One should keep in mind that aldosteronism also develops in primary renovascular hypertension but the latter entity is associated with high serum renin levels while in primary aldosteronism the renin levels are low. Hypoaldosteronism is rare. It appears to be due to inadequate stimulation of aldosterone secretion or a defect in the adrenal synthesis of aldosterone. An unusual cause of secondary hypoaldosteronism (called pseudohypoaldosteronism by some) is seen in some infants with urinary tract infection, with or without urinary tract obstruction. Clinically, hypoaldosteronism results in hypotension and hyperkalemia. Imaging has no role in its diagnosis.
Imaging A distinction between unilateral aldosteronomas, which are treated surgically, and bilateral hyperplasia, treated medically, is of obvious importance. The adrenal glands are significantly larger in patients with bilateral adrenal hyperplasia than in those with an aldosteronoma. One study achieved 100% sensitivity when a CT mean limb width of >3mm was used to diagnose bilateral adrenal hyperplasia, and 100% specificity when limb width was 5mm or greater. Unless imaging identifies a tumor, such differentiation is generally sought by bilateral adrenal venous sampling.
Aldosteronomas tend to be small; discrete nodules are difficult to visualize. Thus among 18 aldosterone-producing adrenal adenomas, 89% were detected with CT but only 28% with US. Adrenal hyperplasia in Conn’s syndrome ranges from diffuse and bilateral to nodular. Thus one or more nodule may represent either an adenoma or nodular hyperplasia. Complicating this picture is the presence of the occasional unrelated incidental adrenal tumor. Similar to Cushing adenomas, aldosteronomas contain varying amounts of lipid. As a result, some have CT attenuation values close to that of water and their CT appearance can mimic a cyst.
Calcifications develop only in an occasional benign aldosteronoma.
In 20 patients with primary hyperaldosteronism, 50% had aldosterone-producing adenomas and 50% bilateral adrenal hyperplasia; MRI detected adenomas with a sensitivity of 70% and specificity of 100%, with adenomas being iso- to hypointense relative to liver on T1- and slightly hyperintense on T2-weighted images. Of interest is that signal intensity decreased on out-of-phase chemical shift
images in 86% of adenomas and 89% of adrenal hyperplasia, indicating the presence of lipid. Iodine-131–NP-59 scintigraphy appears to be complementary to CT and MR in differentiating between adenomas and adrenal hyperplasia, being especially useful with a unilateral hyperplastic nodule. Scintigraphy visualizes these tumors as hot nodules,with an occasional warm nodule.
Bilateral adrenal venous sampling distinguishes most but not all adenomas from hyperplasia. Blood samples are obtained after stimulation with ACTH. With bilateral hyperplasia, after stimulation aldosterone levels increase in blood samples from both adrenals; on the other hand, a more marked unilateral increase is detected with an aldosteronoma.
image
Radiology images of the Conn’s syndrome. Computed tomography (CT) reveals bilateral adrenal hyperplasia.

Therapy Patients with bilateral glomerulosa hyperplasia and those amenable to glucocorticoid therapy are treated medically. Adenomas are resected, but keep in mind that hypertension persists in 30% to 50% of patients after resection even if they are biochemically cured. Such persistent postoperative hypertension suggests coexisting essential hypertension. Several patients with Conn syndrome and Cushing’s syndrome have been treated by CTguided acetic acid injected into their adrenal nodules; follow-up revealed cystic degeneration. A few aldosteronomas have also been treated by transcatheter arterial embolization with absolute ethanol.
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