Congenital or primary communicating hydrocele arise in the peritoneum-vaginal canal. Through this canal and over time, the peritoneal cavity is in contact with the vaginal membrane of the testis. Under normal conditions, the peritoneum-vaginal canal closes before birth but when it does not close and the opening is small, only peritoneal fluid may pass, resulting in a hydrocele. Congenital hydrocele is more common in children. Secondary hydrocele arises from an imbalance between the lubricating fluid oozing from the testis and re-absorption by the vaginal membrane. In some circumstances, such as trauma or infection, but often without any apparent cause, the serous bag has difficulty reabsorbing the fluid. As a result, there is progressive accumulation of fluid inside the bag, resulting in a hydrocele. Secondary hydrocele is more common in adolescents and adults, although it may also occur in children.