[Polyuria as postoperative complication of frontal meningioma].

We report the case of a 56-year-old man with a frontal meningioma who underwent scheduled surgery under balanced general anesthesia without complications and was then transferred to the intensive care postoperative recovery unit for observation. On the day of admission he developed polyuria and a decrease in central venous pressure. Plasma sodium and osmolarity were in the normal ranges but urine analysis showed hyponatremia and hypo-osmolarity, suggesting cerebral salt wasting syndrome. Physiological saline solution was infused to maintain osmolarity and plasma concentrations of sodium within normal ranges. Diuresis peaked on the sixth day after surgery at 17,600 mL in 24 hours and decreased gradually to normal on the eleventh day after admission. Elevated plasma concentrations of atrial natriuretic peptides confirmed the diagnosis. Correct management is essential when neurosurgery patients develop altered plasma and urinary sodium concentrations and osmolarity. Differential diagnosis involves considering diabetes insipidus, inappropriate secretion of antidiuretic hormone and salt wasting syndrome. Transfer to an intensive care postoperative recovery unit and early treatment are important for lowering the risk of complications and death.