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.
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."