Based on the pro-inflammatory role of AQP2 in glial cells, we assumed that lower expression of AQP2 in peripheral serum might indirectly indicate lower AQP2 excretion but higher AQP2 expression in peripheral blood cells or CNS, which aggravates central immune microenvironment dysfunction after a hemorrhagic stroke along with poor prognosis. Here, AQP2 is linked to hemorrhagic stroke.