Well im not a doctor or anything but i did learn how people get rid of there waste. Diareah sits in your large intestine untill all the water is sucked out, then cleaned and then reused. At this time it would enter the rectum and sit untill ready for disposel. Yet if your body has too much water stored up. It will let the direah into the Rectum which is what the anus is coneted to and there fore leaking water into your vagina which would be pretty nasty.
I dont got a degree ins cience this is all from high school and what i have learned.