shy kidneys 

When you can't pee in the presence of other people.

I can't piss in this urinal, because i have shy kidneys.

shy kidneys by blinded October 7, 2008

kidney shy 

adjective describing the delayed ability to urinate in a public restroom, usually caused by the misapprehension that other people will hear you pee.

Woman returning from the restroom on Girls' Night Out: "Sorry I took so long. There were so many people in there, I got kidney shy."

kidney shy by N. Fritz May 9, 2008