What causes seminal vesicle enlargement?

Duct obstruction: Ejaculatory duct obstruction (EDO) is a congenital or acquired pathological condition which is characterized by the obstruction of one or both ejaculatory ducts. Thus, the efflux of (most constituents of) semen is not possible. It is a cause of male infertility and / or pelvic pain. This can cause enlargement of the seminal vesicles. See a urologist.