By the time he's in first grade he'll totally understand that that which we drink is that which we pee and he will absolutely INSIST! DAMMIT INSIST that if he drinks a whole carton of milk at lunch he must have to pee it back out ten minutes later. Being told 'we just took a bathroom break before lunch' is irrelevant because he JUST drank a WHOLE HALF pint of milk and now it's an EMERGENCY!

*sigh*

Kids and kidneys. Fun times. :)