Kidney occult blood actually refers to the clinical urine routine examination inside the urine occult blood is positive, generally urine occult blood positive means that after centrifugation, the number of red blood cells per high magnification field of view in the urine is greater than 3 or more. There are many causes of urinary occult blood: first, nephritis, clinical acute nephritis, acute glomerulonephritis and chronic glomerulonephritis, can lead to positive urinary occult blood. Second, urinary stones, such as kidney stones, ureteral stones, etc. will lead to positive urine occult blood. Third, tumors of the urinary system can lead to positive urine occult blood. Fourth, patients with urinary tract infections can also lead to positive urine occult blood, in addition to the results of positive leukocytes, patients often combined with the symptoms of urinary frequency, urinary urgency, urinary pain. Fifth, for example, like after strenuous exercise or long and thin adolescents can lead to the phenomenon of nutcracker, which causes urinary occult blood.