Hyponatraemia

Syndrome of inappropriate antidiuretic hormone release (SIADH) is a condition defined by the unsuppressed release of antidiuretic hormone (ADH) from the pituitary gland or nonpituitary sources or its continued action on vasopressin receptors. Of the many causes of SIADH, an important one includes tumours that secrete ADH. We describe a rare case of a patient with colonic adenocarcinoma presenting initially as SIADH. A 60-year-old man presented with confusion and vomiting. Over the previous month he had fatigue and loss of weight.

Hyponatraemia is present in 15–20% of non-selected emergency admissions to hospitals in the UK. It is associated with increased mortality and morbidity as well as increased duration of stay, independent of the cause for admission. Hyponatraemia is therefore common and important, driving the need for a rational but practical management strategy. This must encompass a stratified approach based on clinical presentation, balancing diagnostic uncertainty and the relative merits of different interventions to achieve the best outcome.