HYPONATRAEMIA

decreased total body Na [hypovolaemic hyponatraemia]:

salt loss:

renal:

diabetic ketoacidosis

git losses:

ileostomy

excess free water [dilutional hyponatraemia]:

SIADH [normo- or hypervolaemic; various causes]

any cause of salt and water loss with replacement of water alone [normovolaemic]

relative water retention [hypervolaemic; total body NaCl usually normal or high; causes are as those of oedema, eg. nephrotic syndrome, CHF, cirrhosis]

pseudohyponatraemia:

hyperproteinaemia