CLINICAL DIAGNOSTIC MANUAL
Hyponatremia is defined as a decrease in plasma sodium concentration below 135 mmol/L. This condition is one of the most common electrolyte disturbances in clinical practice and can have various causes.
Hyponatremia can be acute or chronic and may be associated with different levels of extracellular volume, including hypovolemia, normovolemia, and hypervolemia.
Symptoms of hyponatremia can range from asymptomatic to severe, including serious neurological manifestations such as seizures and coma. The management of hyponatremia depends on identifying the underlying cause and assessing the patient’s volume status.
Pathology | Clinical Symptoms and Signs | Suspected Diagnosis | Confirmatory Diagnosis |
|---|---|---|---|
Hypotonic plasma with hypovolemia due to fluid loss | Orthostatic hypotension, tachycardia, dry skin, intense thirst, confusion | History of fluid loss (diarrhoea, vomiting, sweating) | Serum electrolyte measurement, urinary osmolality, BUN/creatinine |
Hypotonic plasma with normovolemia | Confusion, lethargy, muscle weakness, headache, seizures | History of chronic illness, use of certain medications | Plasma and urine osmolality, thyroid and adrenal function tests, water restriction test |
Hypotonic serum with hypervolemia | Edema, ascites, shortness of breath, confusion, muscle weakness | History of heart failure, liver cirrhosis, nephrotic syndrome | Serum electrolyte measurement, plasma osmolality, cardiac and liver evaluation |
Syndrome of Inappropriate ADH Secretion (SIADH) | Confusion, lethargy, nausea, vomiting, seizures | History of cancer, infections, use of medications that stimulate ADH | ADH measurement, urinary and plasma osmolality, evaluation of underlying causes |
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