Urine red blood cell examination is of great significance for the diagnosis of glomerulonephritis, acute cystitis, renal tuberculosis, kidney calculi's disease, pyelonephritis, renal tumor, renal trauma and other diseases. It is also of great value in the differential diagnosis of acute and chronic glomerulonephritis or nephropathy, and renal hematuria and non-renal hematuria can be distinguished by the morphology of urine red blood cells. Since the morphological changes of red blood cells in fresh urine were used to distinguish renal hematuria from non-renal hematuria, many people have done clinical research and found that there are at least two morphological changes of red blood cells in renal hematuria, namely, changes in the size and morphology of red blood cells and changes in the distribution and content of Hb in red blood cells.

The size and morphology of red blood cells in non-renal hematuria are consistent, and the red blood cells are mainly single normal morphology. In addition to pathological factors, the changes of urine osmotic pressure and urine pH can also lead to the changes of erythrocyte morphology. In alkaline urine, the surface of lipid outer layer of erythrocyte membrane increases, and sawtooth-shaped erythrocytes and spiny erythrocytes appear. In acidic urine, the surface of lipid inner layer of red blood cells increases, and reversible mouth-shaped red blood cells or cells dissolve and destroy. In hypotonic urine, doughnut-shaped and ring-shaped red blood cells appear and are easy to hemolyze; In hypertonic urine, due to the concentration of urine, red blood cells can shrink like mulberry. Microscopic examination of urine sediment is a reference standard for urine red blood cell examination, which can not only quantitatively analyze red blood cells, but also observe the morphological changes of red blood cells. It is an important diagnostic basis for kidney and urinary system diseases and an important content for standardizing urine analysis. However, its shortcomings are: (1) The standardized microscopic examination of urine sediment is complicated.

(2) Some red blood cells remain in the kidney for a long time, and are broken by mechanical action or hemolyzed in blood vessels, forming Hb urine, which cannot be detected.