Scarleteen

Does pre-ejaculate necessarily come out of penis upon erection or it is limited in urethra???I mean upon usual arousal,does it remains in urethra or come out of it???

Pre-ejaculate's function is basically to clear the urethra of anything that is a problem for sperm cells - like urine, for example. So, when it occurs, it does typically go through that tract until it comes out from the opening of the penis.