When you're getting fisted, your ass is opened up good and the fister pummels your prostate so hard you start contracting with an anal Orgasm and lose control of your bladder... You literally shoot waves of piss and precum all over the place.
Make sure you put down a couple towels when you get fisted with a full bladder so your pissgasm doesn't soak the bed.
After holding in a piss for a long time, once it is released it feels like a mini orgasam. Also noted the hand on the wall or the closed eyes with grunting are common signs of a pissgasam.
"After that 64 ounce Mountain Dew during the 4 hour car drive, once i was able to drain my lizard i had a major pissgasam."