Hyponatremia laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Saeedeh Kowsarnia M.D.[2]

Overview

An elevated/reduced concentration of serum/blood/urinary/CSF/other [lab test] is diagnostic of [disease name].

OR

Laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].

OR

[Test] is usually normal among patients with [disease name].

OR

Some patients with [disease name] may have elevated/reduced concentration of [test], which is usually suggestive of [progression/complication].

OR

There are no diagnostic laboratory findings associated with [disease name].

Laboratory Findings

Biochemical evaluation for finding cause of hyponatremia :

• Serum sodium
• Serum osmolality
• Serum potassium
• Serum chloride
• Serum creatinine
• Serum other solutes
• Serum urea
• Blood Glucose
• Total protein and albumin
• Serum lipids
• Total bilirubin and direct bilirubin
• red and white cell blood count
• Serum cortisol
• Adrenocorticotropine hormone
• ADH level
• TSH
• Urine sodium
• Urine chloride
• Urine osmolality
• Urine for other solutes
• Fraction excretion of sodium
• Calculate GFR

Characteristics	Hypervolemic Hyponatremia	Euvolemic Hyponatremia	Hypovolemic Hyponatremia
Total body water	↑↑	↑	↔
Serum sodium level	↑	↔	↓↓
Plasma Osmolality, mOsm/kg	< 280	<280	≥ 280
Urine Osmolality, mOsm/L	> 100	> 100	> 500
Urine sodium level, mEq/L	< 20 or >20	> 20	< 10 or > 20
Differentiation of causes	> 20 mEq/L urinary sodium: Acute or chronic renal failure Fluid overload Psychogenic polydipsia < 20 mEq/L urinary sodium: Heart failure Cirrhosis Nephritic syndrome	SIADH/SIAD Adrenal insufficiency Hypothyroidism Drugs	< 10 mEq/L urinary sodium: Diuretics Extrarenal loss such as diarrhea, vomiting Severe hyperglycemia Third spacing of fluids > 20 mEq/L urinary sodium: Adrenal insufficiency Renal bicarbonate loss(renal tubal acidosis, metabolic alkalosis) Renal sodium loss (cerebral salt wasting, salt-wasting nephropathy) Diuretics

• There are no diagnostic laboratory findings associated with [disease name].

OR

• An elevated/reduced concentration of serum/blood/urinary/CSF/other [lab test] is diagnostic of [disease name].
• [Test] is usually normal among patients with [disease name].
• Laboratory findings consistent with the diagnosis of [disease name] include:
  • [Abnormal test 1]
  • [Abnormal test 2]
  • [Abnormal test 3]

• Some patients with [disease name] may have elevated/reduced concentration of [test], which is usually suggestive of [progression/complication].