When plenty is too much: water intoxication in a patient with a simple urinary tract infection

Healthcare professionals frequently advise patients with simple infective illness to drink more fluids. Here, a 59-year-old woman with a urinary tract infection followed such advice resulting in hospital admission with symptomatic acute hyponatraemia. Water intoxication is well recognised as a cause of symptomatic hyponatraemia in endurance sports, MDMA use and psychogenic polydipsia. It has rarely been described outside of these circumstances. With normal renal function, it is difficult to overwhelm the excretory capacity for water. However, in infective illness, increased levels of antidiuretic hormones (which may be secreted both appropriately to correct volume status and inappropriately as a feature of disease) reduce renal excretion of water. In this scenario, could increased administration of oral hypotonic fluids lead to hyponatraemia, with associated morbidity and mortality, than has previously been recognised? There is a need for more research to qualify our oft-given advise to drink more fluids.