Uhm... I don't know how long you think an emergency will last. Let's call it 14 hours, for the sake of argument. I base that on having an approximately 13.5 hour "night" for both of us, less that first hour you spend blundering about thinking you are right next to the parking lot, but plus hour and half that you spend in the morning actually getting there.

Fishmode, if you are willing to conduct a test, from the moment you read this, for the next 14 hours, you are NOT to urinate. I hope you peed before you checked this.

Honestly, I don't think you can do it. I think your bladder will whine, complain, and eventually grab you by the nose and say point blank "look buddy, I'm full, I'm going to be emptied- your call how and where, but the when is going to be in the next sixty seconds." If it has been more than ten hours since your last pee, you are probably in trouble.