Prevalence
Causes
Clinical
features
Investigations
Therapy
Prognosis
|  | | | Causes |
Causes of hyponatraemia
| Dehydration |
No
dehydration or oedema |
Oedema |
| renal losses |
artefact |
congestive heart failure |
| diuretics |
sample taken iv from arm |
nephrotic syndrome |
| adrenal insufficiency |
|
cirrhosis |
| osmotic diuresis (glucose, urea, mannitol) |
pseudohyponatraemia |
renal failure |
| renal tubular acidosis |
hyperglycaemia |
|
| |
hypertriglyceridaemia |
|
| fluid loss |
hyperproteinaemia |
|
| vomiting, diarrhoea |
|
|
| sweating |
acute onset |
|
| |
excess intravenous intake post-operatively |
|
| |
psychogenic polydipsia |
|
| |
|
|
| |
chronic onset |
|
| |
syndrome of inappropriate ADH secretion (SIADH) |
|
| |
hypothyroidism |
|
| |
glucocorticoid deficiency |
|
| |
pain, emotion or drugs |
|
Syndrome of inappropriate ADH secretion
SIADH is diagnosed when all of the following are present
d
-
a low serum sodium
-
a concentrated urine and dilute plasma (urine osmolality >100 mOsm/kg,
plasma osmolality <270 mOsm/ kg)
-
a normal circulating volume (no postural hypotension, normal CVP, no pre-renal failure)
-
normal renal, adrenal and thyroid function
d
Causes include 
d
-
Cancers: oat cell of lung, duodenum, pancreas, thymus, brain
-
Infections: pneumonia, CNS, tuberculosis
-
Brain injury: stroke, tumour,
haemorrhage
-
Drugs: commonly diuretics, carbemazepine, psychotropics
|
internal medicine