Hematuria, as the name implies, is the presence of blood in the urine. If the number of red blood cells in the sediment is ≥3/HP (high magnification field), it is hematuria. 1, hematuria is divided into microscopic hematuria and carnal hematuria Mild hematuria, although the increase of red blood cells in the urine, but the naked eye observation is normal, only under the microscope to see, called microscopic hematuria; serious hematuria, a large number of red cells in the urine, the color of urine into a wash of water or soy sauce color, or even bright red and blood clots, called carnal hematuria. It is usually visible to the naked eye when there is 1ml of blood per liter of urine. 2, red urine is not necessarily hematuria After eating certain foods (such as beets) or taking certain drugs (such as rifampin, aminopyrine, etc.), the urine is also red; when the urine contains a large amount of uric acid salts, the urine may also precipitate red crystals after cooling, but this is not hematuria. When you encounter this situation, you must do a microscopic examination of urine sediment. 3, urine occult blood positive is not necessarily hematuria Urine occult blood test is based on the principle that hemoglobin in the urine reacts with the reagent on the test paper, causing a change in the color of the reagent to read whether the urine contains hemoglobin. The darker the change in color, the higher the grade of occult blood. However, strong oxidizing agents in the urine and a large number of bacteria can also cause a change in the color of the test paper, and the filtration of hemoglobin produced by intravascular hemolysis into the urine also causes a reaction, which is not related to the red blood cells in the urine. Therefore, a positive urine occult blood, no matter how many “+” is not necessarily hematuria. 4, hematuria is divided into renal hematuria and extra-renal hematuria Red cells found in the urine must be examined with a phase contrast microscope to determine the morphology of the red cells from the kidneys or extra-renal. Red blood cells from the kidney often lose their normal morphology and become ring-shaped, target-shaped, bud-cell-shaped or crumpled due to extrusion by the filtration membrane, called aberrant red blood cells. If most of the red blood cells in urine are aberrant red blood cells, the number of aberrant cells > 60% (some say > 70%), it can be considered that the red blood cells come from the kidney, called nephrogenic hematuria, commonly in various kidney diseases such as glomerulonephritis, hypertensive nephropathy, allergic purpura nephropathy, etc.; if most of the red blood cells in urine are normal red blood cells, it means that the red blood cells come from outside the kidney, called non-nephrogenic hematuria, commonly in inflammation, nodules, stones, tumors, trauma and other extra-renal diseases. Note: Diabetic nephropathy does not show renal hematuria. 5.Localization of hematuria Initial hematuria: hematuria is only seen at the beginning of urination, and the lesion is mostly in the urethra; Terminal hematuria: hematuria appears at the end of urination, and the lesion is mostly in the bladder triangle, bladder neck or posterior urethra; Total hematuria: hematuria appears in the whole process of urination, and the bleeding site is mostly in the bladder, ureter or kidney, among which the whole process of painless carnal hematuria is a typical manifestation of kidney cancer and bladder cancer. 6. Simple renal hematuria is not terrible Simple renal hematuria, if there is no urinary protein and no hypertension, is usually seen in occult glomerulonephritis, or familial thin basement membrane nephropathy. These two diseases have lifelong hematuria, but it usually does not develop seriously, so there is no need to be afraid, and it can even be treated without treatment, just regular checkups can be done.