Hey Muffin, i had an op on my kidney years ago and when I drink certain things my left one really kills me but not water, mostly beers, cider and coors light! i'm made to be a vodka redbull girl mmmm!!
You really need to get it checked out cos it's one of the things on the form they ask about-kidneys-.
Also make sure you pee whenever you need to, don't hold it at all!