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Dilutional hyponatremia (SIADH)
Alternative namesSyndrome of inappropriate antidiuretic hormone secretion; SIADH
DefinitionDilutional hyponatremia is a disorder of fluid and electrolyte balance caused by excessive release of antidiuretic hormone (ADH).
Causes, incidence, and risk factors
Fluid and electrolyte imbalance in this syndrome result from the inability to excrete dilute urine, retention of water within the body, and low sodium levels. The most common cause of SIADH is a type of lung cancer called "oat cell" or small cell, which secretes excessive ADH .
Other causes are pancreatic cancer , prostate cancer , Hodgkin's disease , central nervous system disorders, pulmonary disorders, certain drugs, thymomas, myxedema , and psychosis . SIADH may also develop in some children during the acute phase of meningitis . Risk factors are related to the causes.
Signs and tests
TreatmentThe first line of treatment is to restrict fluid intake to one-half or one liter of fluid per day. The cause of the disorder must be treated, especially in the case of malignancy where radiation, chemotherapy , or surgical removal of the tumor may correct the water retention.
Expectations (prognosis)The outcome is related to the underlying disease.
Calling your health care providerCall your health care provider if symptoms of dilutional hyponatremia occur.
PreventionPrompt treatment of causative conditions may be helpful.
Update Date: 10/28/2003Irfan A. Agha, M.D., Department of Medicine, Renal Division, St. Louis University, St. Louis, MO. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT