 <unk> by urine test strip may reveal a positive result for " blood " , even though no red blood cells can be identified on microscopy of the urine ; this occurs because the reagent on the test strip reacts with myoglobin . The same phenomenon may happen in conditions that lead to hemolysis , the destruction of red blood cells ; in hemolysis the blood serum is also visibly discolored , while in rhabdomyolysis it is normal . If kidney damage has occurred , microscopy of the urine also reveals urinary casts that appear pigmented and granular . 
