According to the number of red blood cells in urine, there are generally two types of hematuria: microscopic hematuria and naked eye hematuria. Microscopic hematuria is defined as the number of red blood cells in one high magnification field of the microscope is below 40, and every 10 counted as (+), 20 counted as (++) and 40 counted as (++++) in one high magnification field. (++++) below the hematuria, generally the naked eye observation can not be found, for the microscopic hematuria, 4 + or more, the naked eye that can see the urine is red, by microscopic examination of the number of red blood cells more than 40, for the carnal hematuria. Causes of hematuria 1, kidney and urinary tract diseases fold (1) inflammation: acute and chronic glomerulonephritis, acute and chronic pyelonephritis, acute cystitis, urethritis, urinary tuberculosis, urinary system mycobacterial infection, etc. (2) stones: renal pelvis, ureter, bladder, urethra, any part of the stone, when the stone moves through the urinary tract epithelium, that is easy to cause hematuria also easy to secondary infection. Large stones can cause urinary tract obstruction and even renal function damage. (3) Tumor: Malignant tumor in any part of the urinary system or malignant tumor in adjacent organs invading the urinary tract can cause hematuria to occur. (4) Trauma: It refers to violence and injury to the urinary system. (5) Drug stimulation: such as sulfonamide, phenol, mercury, lead, arsenic poisoning, massive infusion of mannitol, glycerol, etc. (6) Congenital malformations: polycystic kidney, congenital ultra-thin glomerular basement membrane, nephritis. Nutcracker phenomenon, the disease is a congenital malformation of blood vessels caused by the extrusion of the left renal vein traveling between the abdominal aorta and superior mesenteric artery, causing intractable microscopic hematuria called nutcracker phenomenon. The right renal vein injects directly into the inferior vena cava, while the left renal vein must cross the angle formed by the abdominal aorta and superior mesenteric artery to inject into the inferior vena cava. Normally, this angle is 45°~60°, but if this angle is congenitally too small or filled with mesenteric fat, enlarged lymph nodes or peritoneum, it can cause nutcracker phenomenon. Diagnosis is based on CT, ultrasound, and renal venography. Treatment shall be surgically corrected. (2) Systemic diseases: systemic lupus erythematosus, dermatomyositis, polyarteritis nodosa, scleroderma, etc. (3) Infectious diseases: leptospirosis, epidemic hemorrhagic fever, filariasis, infectious bacterial endocarditis, scarlet fever, etc. (4) Cardiovascular diseases: congestive heart failure, renal embolism, renal vein thrombosis. (5) Endocrine metabolic diseases: gout kidney, diabetic nephropathy, hyperparathyroidism.