Another urine discoloration possibility: rhabdomyolysis with myoglobinuria. Muscle tissue destruction with excretion of muscle-iron moleculesin the urine. Dehydration plus exercise may cause this, and it in turn may cause kidney damage. Recently saw such in an aging jock who took a spinning class-resulting in incapacitating thigh cramps, discolored urine, and hospitalization for aggressive rehydration and monitoring of kidney function. happy ending, by the way. hydrate or die, and some of the deaths are prolonged, messy ones.