Pathology: Inappropriate anti-diuretichormone secretion leading to water retention and relative hyponatraemia.
Aetiology: Idiopathic
Endocrine:Hypothyroidism, Addison’s Disease
Ectopic Production:Small cell lung cancer, pneumonia, abscess, TB
Malignancy: Lung,pancreas, ovary, lymphoma, thymoma
CNS: Tumour,trauma, infection, strike, multiple sclerosis, Guillain-Barre
Syndrome,meningitis, encephalitis, subarachnoid haemhorrhage
Drugs: SSRIs,TCAs, opiates, haloperidol, MAOIs, diuretics, NSAIDs
Symptoms: Fatigue, confusion, falls,seizures, inappropriate thirst, headache, nausea
Signs: Weakness, coma,euvolaemia, papilloedema, myoclonus, ataxia, tremor
Investigations: Bloods:U&E – hyponatramia, serum osmolarity, TFTs and Cortisol
MSU: Urinarysodium (raised) and osmolarity
Imaging: CT headto assess for malignancy
Treatment: Fluid restriction, Demeclocycline
Complications: Central pontinemyelinolysis with rapid correction; to prevent this a sodium
correctionrate of 0.5-1mmol/hour should be used
Prognosis: Usually good for idiopathicor drug related causes
