Whats the cause or hydrocele recurrence?

Residual hydrocele: A residual hydrocele sac is the most likely cause. Your procedure was likely performed through a scrotal incision. In adults a hydrocele is a fluid collection around the testes confined to a potential space called the tunica vaginalis which when fills with fluid is call a hydrocele sac. The fluid and most of the sac are removed during the repair but if some sac remains recurrence may occur.