Ahydrocele is sac that is filled with fluid which forms on a testicle. It causes inflammation or swelling in the scrotum. They are most common in babies, but can affect males of any age. In adult men, it often affects those that are middle-aged or older.They are not a very serious condition as there are not any severe complications associated with the condition unless they are associated with an infection, tumor, or inguinal hernia.