retrograde ejaculation
Retrograde ejaculation is when semen fails to be pushed out of the penis, whether because of some blockage along the urethra or an imbalance between the urethral sphincters before and after the prostate, and instead backflows somewhere else. In real life, that means it ends up in the bladder, but in fantasy it could also end up flowing back out of a second urethra or somehow back into the testicles.