Vasa efferentia is the duct that carries the sperms from testis to epididymis. The path of the transport of sperm is: It is produced in seminiferous tubules, then it is transported to rete testis. From there, it is transported to epididymis via vasa efferentia. So, if vasa efferentia is blocked, then sperms will not be able to enter epididymis from testis.