For the last few years, heat related injuries among troops in Iraq and Afghanistan have become a growing problem. Not just the obvious ones, like heat stroke, or simply dizziness and loss of energy, but extremely painful conditions like kidney stones.
Most hot regions, especially those that are largely desert, have lots of people with kidney stones. This affliction is caused by people sweating too much and not replacing the lost liquids quickly enough. Nomads in Arabia (especially Saudi Arabia) were much afflicted by kidney stones, especially because it was a point of honor to go long periods, while traveling across waterless terrain, without taking a drink. Very macho, and the best way to get kidney stones.
U.S. troops in Afghanistan and Iraq have access to lots of water. But often not enough, not when you are running around wearing 30 kg (66 pounds) of armor and equipment, carrying 10 kg (22 pounds) of weapons and ammo. In the Summer, most troops can adapt to the heat. But for hundreds, their kidneys cannot. It got so bad in Iraq, that a special kidney stone smashing machine (that did it without surgery) was brought in, so most victims would not have to be flown out for treatment.
In some respects, the situation is worse in Afghanistan, where there is more running up hills, and keeping water stocks high is difficult. There is no easy solution for the problem.