[Dysnatremia induced by urinary tract obstruction and postobstructive diuresis].

Hyponatremia is a rare but potentially severe complication of acute urinary retention. It causes antidiuretic hormone (ADH) secretion secondary to the pain generated by the obstruction, but also following bladder distension by stimulation of the sympathetic transmission pathways. Once the obstruction is removed, ADH secretion stops immediately, leading to spontaneous and very rapid correction of hyponatremia given the hormone's short plasma half-life. Acute urinary retention may be complicated by postobstructive diuresis, characterized by massive diuresis with dehydration. In cases of preexisting hyponatremia, correction may be all the more rapid if urinary retention is followed by postobstructive diuresis, and careful medical monitoring is required.