What Is It?
Ejaculation is the ejection of semen out of the urethra (passageway inside the penis) when a man has an orgasm. Under normal circumstances, ejaculation propels semen forward through a man's urethra and out the tip of his penis. This is because a tiny sphincter (circular muscle) at the entrance to the bladder shuts the opening to the bladder and prevents semen from entering. Retrograde ejaculation is when the semen travels backwards into the bladder.
In retrograde ejaculation, the muscle that shuts the bladder does not function normally. This allows all or part of the semen to travel backward (retrograde) into the bladder at the time of ejaculation. When this happens, less semen comes out the tip of the penis.