There was a movie called Last House on the left. I understand it was remade not too long ago with Bill Paxton. Haven't seen it but in the original there was a scene where a girl who was kidnapped was forced to pee her pants in front of them. Looked very genuine.
The movie itself was extremely creepy.
There was a cute scene in Doc Hollywood where Michael J. Fox and Julie Werner are peeing on trees to keep deer away from a hunting stand.