Problem based review: the patient presenting with hyponatraemia.

Hyponatraemia is the most common electrolyte anomaly and is associated with significant morbidity and mortality. Patients with severe hyponatraemia often present to acute medical units with non-specific symptoms which can progress to overt neurological manifestations. There are many causes of hyponatriaemia, the most common being drug-induced causes, particularly thiazide diuretics, and the Syndrome of Inappropriate ADH Secretion (SIADH). Initial assessment should include a careful evaluation of the patient's volume status, which helps to identify the most likely cause. This article utilises a recent case which presented to our AMU to illustrate the importance of a careful and systematic assessment of patients presenting to hospital with hyponatraemia. The new vasopressin receptor antagonists are explored as an option for the management of severe hyponatraemia.