The condition is rhabdomyolysis:
> [...] a rare but life-threatening condition often caused by extreme exercise. It occurs when overworked muscles begin to die and leak their contents into the bloodstream, straining the kidneys and causing severe pain.
I've done some extreme things and I've never experienced this. IMO you have to ignore some pretty serious warning signs to even get close to having this problem. Be sane, people.
My sister got this after a particularly grueling Crossfit session. She chalked it up to her being sore but her fiancé is a pediatrician and recognized the symptoms. Had she gone another 24 hours without treatment she could have destroyed her kidneys.