Hyponatraemia

Last updated: Tuesday, 14, December, 2010
CausesAppropriate Tests

Hyponatraemia may occur with dilution of plasma sodium (total body sodium may be normal or increased) or withdehydration and excess sodium loss.

Excessive sodium loss may be renal or extra-renal and the effect may be exacerbated by replacement with oral or IV fluids containing little or no sodium.

Electrolytes, urea, creatinine; sodium - urine.

Artefactual result 

See Table 1.

Osmolality; urine - osmolality, sodium.

Dilutional / Water (fluid) overload 

Cardiac failure

Cirrhosis

Renal failure

SIADH

Hypothyroidism

Hyperglycaemia

Sodium depletion

Renal sodium loss

Diuretic therapy

Idiosyncratic response.

Salt-wasting renal disease

 See Renal tubular disorders

Post-obstructive uropathy

Creatinine, urea; urine - sodium, potassium, osmolality.

Mineralocorticoid deficiency.

See Adrenocortical insufficiency

Extra-renal losses and/or sequestration

Operative blood/fluid loss

Ascites

Sweating, especially

Burn injury 

See Burns