Hmmm...

I do know that NASA studies of the heat economy of the human body noted that waste products combined amounted to about 2% of the total heat loss. I remember this because it is one of those oddball useless factoids.

Heat loss from head and neck amounted to something like 50% of the heat loss. IMHO the lesson is that your better off putting on a hat and winding on a scarf than worrying too much about what your losing when you pee.

Holding your water when water is short has some logic to it but I think the body does this pretty much automatically without having to burden yourself with consciously holding water.

While generally the bladder is viewed as just a holding tank, with little if any absorption ability, I wonder if this is the whole picture. Many times I have climbed into a hot enclosed space, 150F or so (I used to carry a thermometer before it dawned on me that Too Hot wasn't made any better by knowing the actual number.), when I could take a pee. Nothing desperate but a moderately full bladder.

I climb in thinking it will be just a couple of minutes. Half an hour or more later I'm fully cooked. When I come out all I can do is sit down, cool off, sip water and embrace the brain damage. Somewhere along the line I notice that while I could pee before I went in I have no urge to after I get out. I have sweat out something like a liter of water. And now I will drink another liter or two before I feel the need.

Seems to me that the contents of the bladder had to go somewhere. And if the bladder and body can do this on its own there really isn't much need to second guess the system. IMO it amounts to the body knowing what it is doing.

Also It has been said that he brain is your most important survival tool. I don't know about you but I can't much think straight while clenching my loins and hopping from foot to foot like a fool trying to hang onto a few ounces of polluted water.

IMO if your body demands that you empty your bladder your better off saluting and complying instead of second guessing.