I don't believe it is an issue either. Like somebody else above, I recall an article about urine from somewhere a few years ago that got fairly scientific about what is in urine and how it is percieved by critters. If I recall correctly, the important stuff like doe estrus doesn't last much over an hour or so before it is gone. I believe the consensus was that deer may be able to tell human urine from animal urine based on your diet but only for a short time. Like somebody else said, meat eaters uirine smells different (supposedly) than herbivore urine but again, only for a while. Even so, there are a LOT of meat eaters running around the woods. Coyotes, bobcats, dogs, even coons, opossums etc. Never heard of a deer spooking from there urine. If they did, they'd NEVER have a moments peace.
I even pee when I'm hunting from my double bull ground blind but I have one little trick for that situation. I carry a cheap metal or plastic garden trowel that my wife uses to plant flowers in the spring around the house. Simply dig out a single scoop of dirt like a plug. Going full depth of the trowel gives me about a 6 inch deep hole. I pee in the hole, let it dissapate into the ground and drop the plug of dirt back down and pack it a little to seal it up.
I've done this multiple times in a day and still had deer come in and not spook. One even bedded down within 20 yards. The true test though was when I took the blind down then set it up again a day or two later and still had deer using the area like I'd never been there.