I have a blue card, supposedly readily recognisable to the USA TSA,( hence its obvious colour, apparently ) that indicates that I have a medical condition that may affect the results of any airport screening. It doesn't exempt me from the screening process but explains why bells and whistles might go off, and if so not to jump to any conclusion regarding my possible terrorist status.
The other side of the card is headed " Gotta Go NOW !! " and explains to Cabin Crew that I possess an Ostomy Pouch and need to use the Restroom NOW, and that this is critical, not only for my well-being, but also public sanitation.
The card is issued by the United Ostomy Ass'n. of America Inc.
I gaily wave it at the TSA and have had no issues, neither have I needed to use it for airborne toilet facilities - yet. I assure you that if I do I will be most vociferous in my demand, even to threatening to change my "Bag" in the aisle if necessary ! That'll learn them.