Hyponatraemia caused by transient syndrome of inappropriate antidiuresis to urinary retention

Hyponatraemia is frequently seen in the emergency department, possibly caused by the syndrome of inappropriate antidiuresis (SIAD). We report three cases in which we believe urinary retention with bladder distention caused hyponatraemia. Laboratory findings fulfilled the criteria for SIAD, for which no cause was found. Possibly pain or sympathetic nerve system activation leads to SIAD. Brisk diuresis occurred after placement of an indwelling urinary catheter with overly correction of sodium for which treatment was necessary. Clinicians should be aware that placement of an indwelling urinary catheter may prompt brisk water diuresis and a tendency to overcorrection.