Objective  To investigate the risk factors and formation mechanism of acquired hydrocephalus complicated with hyponatremia (serum sodium < 135 mmol/L).

  Methods  The clinical materials of 41 patients with acquired hydrocephalus were retrospectively analyzed. The risk factors of hyponatremia were analyzed by multiple regression analysis, and its formation mechanism was discussed in combination with the literatures.

  Results  A total of 9 cases with acquired hydrocephalus had hyponatremia, and age and maximum width of the third ventricle before shunt operation were significantly associated with acquired hydrocephalus complicated with hyponatremia (P < 0.05). After adjusting for possible confounding factors, age was the risk factor for acquired hydrocephalus complicated with hyponatremia (OR=1.09, 95%CI, 1.01 to 1.18), while the maximum width of the third ventricle before shunt operation was the protective factor (OR=0.06, 95%CI, 0 to 0.91).

  Conclusion  Age is a risk factor for acquired hydrocephalus complicated with hyponatremia. For elderly patients with acquired hydrocephalus, physicians need to pay attention to the change of blood sodium. Once hyponatremia occurs, timely shunt operation is an effective therapeutic measure.