title: Profound hyponatraemia following an idiosyncratic reaction to diuretics.
abstract: A case report of a79-year-old woman with a breast adenocarcinoma who presented with clouding of consciousness and anorexia with a hyponatraemia of 97 mmol/l is described. An initial diagnosis of secretion of inappropriate antidiuretic hormone (SIADH) was made on the clinical history and a urine: plasma osmolality ratio of 2.25. Further investigation revealed the correct diagnosis of a sodium-losing state with dehydration, and that her ADH level was normal. The actual cause of her hyponatraemia was the recent prescription of a thiazide diuretic. This case illustrates the unreliability of urine: plasma osmolality ratios for the diagnosis of SIADH.
authors.affiliation: Department of Chemical Pathology, Chelsea and Westminster Hospital, London, UK.
authors.forename: A S
authors.initials: AS
authors.lastname: Wierzbicki
authors.forename: S G
authors.initials: SG
authors.lastname: Ball
authors.forename: N K
authors.initials: NK
authors.lastname: Singh
mesh_terms: D000368:Aged; D001581:Benzothiadiazines; D003681:Dehydration / Q000209:etiology; D003951:Diagnostic Errors; D004232:Diuretics; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000139:chemically induced* / Q000175:diagnosis; D007177:Inappropriate ADH Syndrome / Q000175:diagnosis; D009994:Osmolar Concentration; D049993:Sodium Chloride Symporter Inhibitors / Q000009:adverse effects*
chemical_list: D001581:Benzothiadiazines; D004232:Diuretics; D049993:Sodium Chloride Symporter Inhibitors