Syndrome Of Inappropriate ADH

Definition

An excess of endogenous ADH, either cerebral or tumour derived (as a paraneoplastic syndrome)

Presentation

Usually an incidental finding on biochemical investigations, but may present with features of hyponatraemia

Examination

Patients will usually be euvolaemic

Bedside tests

Laboratory investigations

Bloods

U&Es

Renal function is usually normal

Serum osmolality - <270-280mmol/kg

Urine

Urine electrolytes - Urine [Na+] > 40mmol/L

Urine osmolality will be inappropriately high (100>mmol/kg)

Radiological investigations

Differential diagnosis

Tumours

Prostate

CNS disorders

CVA

Trauma

Meningitis / Meningoencephalitis

Pulmonary disorders

Abscess

Drugs

Anticonvulsants (eg carbamazepine)

Antipsychotics (eg haloperidol)

Antidepressants (eg amitriptyline, fluoxetine)

Cytotoxics (eg cyclophosphamide, vincristine)

Opiates (eg morphine)

Thiazides

Prolonged stress, nausea, pain (eg post-operative)

Idiopathic

Management

First line

Second line

Prior to discharge

Follow up

Complications

Central pontine myelinolysis

Prognosis

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