No significant differences were observed in the density of AQP1-expressing capillaries in the tunica vaginalis between the controls and hydrocele patients (27.6 ± 16.2 versus 28.2 ± 16.7/mm2, resp.; mean ± SD; P = 0.92 by an unpaired t-test). Here, AQP1 is linked to testicular hydrocele.