Balls don't really swell when tied. You may be thinking of infusion. That's when sterile saline is injected into the scrotum and it inflates like a balloon- you can really distort the poor subby. (Try a Google search of image search for 'scrotal inflation'.) I've never experienced it, but it's supposed to be quite intense for the subject, and it can't be deflated with a needle. The saline gets into the tissue and must flush out naturally. It can take a couple of days.