Retrograde ejaculation occurs when the sperm is directed into the patient's bladder rather than being directed through the urethra into the semen. Since the patient produces semen, the only way to determine retrograde ejaculation is through a Post-Ejaculatory Urinalysis (PEU). The man ejaculates and immediately afterward urinates into a separate cup. The post-ejaculatory urine is centrifuged to see if any sperm are present.