What causes fetal hydrocele?

Communication. Between perineum and tunica vaginalis surrounding testis. Testes develop at back of abdominal cavity, just below kidneys. They migrate downwards and and out of abdomen through the inguinal canals attached to a slip of peritoneum, the tunica vaginalis at 27 wks. This normally closes after attached testis reaches base of scrotum. Fluid causing collection in scrotum via communication causes hydrocele.