{"id":2185,"date":"2010-01-02T13:07:15","date_gmt":"2010-01-02T18:07:15","guid":{"rendered":"http:\/\/insidesurgery.com\/?p=2185"},"modified":"2013-08-17T14:47:07","modified_gmt":"2013-08-17T18:47:07","slug":"siadh-syndrome-inappropriate-antidiuretic-hormone-secretion","status":"publish","type":"post","link":"https:\/\/insidesurgery.com\/2010\/01\/siadh-syndrome-inappropriate-antidiuretic-hormone-secretion\/","title":{"rendered":"SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion)"},"content":{"rendered":"<p><strong>Pathophysiology<\/strong><\/p>\n<p><strong>1)<\/strong> overproduction of arginine vasopressin (ADH) when physiologically not required <strong>2)<\/strong> causes excess sodium and water retention <strong>3)<\/strong> urine is highly concentrated with decreased output 4) can result from abnormal release from posterior pituitary or from ectopic source<\/p>\n<p><strong>Signs and Symptoms<\/strong><\/p>\n<p><strong>1)<\/strong> edema owing to water retention <strong>2)<\/strong> change in mental status (lethargy, confusion, seizures, coma) <strong>3)<\/strong> headache <strong>4)<\/strong> nauses <strong>5)<\/strong> vomiting <strong>6)<\/strong> can be completely asymptomatic and only picked up by abnormal lab values of hyponatremia<\/p>\n<p><strong>Characteristic Test Findings<\/strong><\/p>\n<p><em>Laboratory<\/em> &#8211; <strong>1)<\/strong> hyponatremia <strong>2)<\/strong> increased atrial natriuretic hormone <strong>3)<\/strong> decreased renin activity <strong>4)<\/strong> increased urinary sodium <strong>5)<\/strong> decreased serum urea and uric acid<\/p>\n<p><strong>Associated Conditions<\/strong><\/p>\n<p><strong>1)<\/strong> neoplasms (oat cell of lung, pancreas, carcinoid) <strong>2)<\/strong> infection (AIDS, aspergillosis, pneumonia, meningitis, encephalitis, tuberculosis) <strong>3)<\/strong> neurologic conditions (stroke, Guillain-Barre syndrome, multiple sclerosis) <strong>4)<\/strong> metabolic causes (head trauma, pneumothorax, acute intermittent porphyria) <strong>5)<\/strong> drugs (ACE inhibitors, selective serotonin reuptake inhibitors, and especially the chemotherapy drugs vincristine and cyclophophamide)<\/p>\n<p><strong>Inheritance\/Epidemiology<\/strong><\/p>\n<p>most common cause of normovolemic hyponatremia<\/p>\n<p><strong>Treatment<\/strong><\/p>\n<p><em>Acute onset<\/em> &#8211; <strong>1)<\/strong> restriction of total fluid intaked <strong>2)<\/strong> hypertonic saline (3%) <strong>3)<\/strong> furosemide diuresis  <em>Chronic onset<\/em> &#8211; <strong>4)<\/strong> demeclocycline or lithium (blunts effect of vasopression on renal tubule) <strong>5)<\/strong> fludrocortisone<\/p>\n<p><strong>Tips for USMLE<\/strong><\/p>\n<p><strong>1)<\/strong> symptoms are those of hyponatremia <strong>2)<\/strong> must not correct hyponatremia more than 12 mmol in 24 hour period as increased risk central pontine myelinosis (delayed onset of ataxia and brain dysfuction <strong>3)<\/strong> SIADH patients are euvolemic <strong>4)<\/strong> before making the diagnosis of SIADH, must exclude thyroid, renal, and adrenal disorders (these patients also have hyponatremia and concentrated urine) <strong>5)<\/strong> for SIADH, look for hyponatremia (sodium < 130 mmol\/L) and concentrated urine (> 300 mOsm\/kg)<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Pathophysiology 1) overproduction of arginine vasopressin (ADH) when physiologically not required 2) causes excess sodium and water retention 3) urine is highly concentrated with decreased output 4) can result from abnormal release from posterior pituitary or from ectopic source Signs and Symptoms 1) edema owing to water retention 2) change in mental status (lethargy, confusion, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[5134,63],"tags":[856,861,864,857,859,863,862,860,855,858],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.5 - 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