The important physiological function of kidney is to produce urine, so the changes in urine are of great importance to reflect the physiology and pathology of kidney, and are important indicators for the diagnosis of kidney disease. In general, most kidney diseases have changes in urine. In addition to the previously described tests of urine protein, urine volume and urine red blood cells, some of the following tests must be done for kidney patients to help diagnose and differential diagnosis. 1.Urine specific gravity: Use urine specific gravity meter for determination. Normal urine specific gravity fluctuates between 1.015 and 1.025. Morning urine is more concentrated, so the specific gravity is higher, often above 1.020. The specific gravity of urine is proportional to the amount of solute contained in urine, when the urine contains too much protein, urine sugar, the measured specific gravity value is higher than the actual urine specific gravity, so it must be corrected. The correction method is that for every 1 g/dL increase in urine protein, the measured urine specific gravity should be reduced by 0.003; for every 1 g/dL increase in urine sugar, the measured urine specific gravity should be reduced by 0.004. The urine specific gravity is also affected by the volume of urine, the temperature and the room temperature at the time of measurement. When drinking a lot of water, urine volume increases, urine specific gravity decreases; when high temperature, sweating more, urine volume decreases, urine specific gravity increases. When measuring the specific gravity of urine, because the temperature of fresh urine is often higher than the room temperature, so generally measured after 30 minutes. If the room temperature is not the same as the standard temperature on the specific gravity meter, the measured urine specific gravity should also be corrected, that is, for every 3℃ above the standard temperature, the measured urine specific gravity will be increased by 0.001; when the temperature is 3℃ below the standard temperature, the measured urine specific gravity will be decreased by 0.001. The urine specific gravity can reflect the concentration function of the kidney, when the urine specific gravity is fixed at 1.010±0.003, it is called isotonic urine or isotonic urine. When the specific gravity of urine is fixed at 1.010±0.003, it is called isotonic urine or isotonic urine, which indicates a serious impairment or loss of renal tubular concentration. Any disease that can affect the change of solute in urine or lead to the change of urine volume will show corresponding change in its urine specific gravity. 2, urine acidity and alkalinity (pH): pH test paper or pH meter is commonly used to determine. Normal urine is generally weakly acidic, with a pH of about 6.5, sometimes neutral or weakly alkaline due to diet and other influences. Acidic or alkaline urine can occur in the presence of disease or medication. When renal tubular acidosis, despite the severity of acidosis, the urine pH does not decrease accordingly, which is important for diagnosis. 3, urine sediment examination: the so-called urine sediment refers to the sediment left after the urine is centrifuged and the supernatant is discarded. Urine sediment, in addition to the examination of red blood cells, should also be carried out the following tests: ① tubular: tubular is the protein in the renal tubule coagulation and the formation of columnar, its size and thickness, depending on the formation of the site. When there is a large number of tubulars in the urine, it indicates pathological changes in the renal parenchyma. Small amounts of clear tubular forms may appear in the urine during strenuous exercise, cardiac insufficiency, high fever, and use of narcotics. The tubular pattern is mostly formed in the distal tubule, and if it is formed in the collecting duct, its tubular pattern is several times larger than the general tubular pattern, and it is mostly seen in chronic renal insufficiency, so it is also called renal failure tubular pattern. The hyaline tubular pattern is formed by the coagulation of Tamm a Horsfall protein secreted by renal tubular epithelial cells, which is mostly seen in the morning concentrated urine of kidney patients. When the tubular pattern is embedded with a cellular component, it is called a cellular tubular pattern. The main types are erythrocyte tubular, leukocyte tubular, and epithelial cell tubular. Erythrocyte tubulars are also called blood or hematocrit tubulars if the red blood cells in the tubulars have disintegrated and are reddish-brown and homogeneous. The presence of erythrocyte tubular pattern in the urine indicates a bleeding lesion in the kidney, which can be common in all kinds of primary or secondary nephritis, while leukocyte tubular pattern is mostly seen in acute pyelonephritis and interstitial nephritis. Epithelial cell tubular pattern is formed by embedding renal tubular epithelial cells, which can be seen when kidney disease damages and renal tubules. Sometimes a variety of cellular components can be seen in the tubular pattern, which is called “mixed cell tubular pattern.” When the cells disintegrate to form granules and are embedded in the tubular pattern, the tubular pattern is called granular tubular pattern, which indicates that there is stagnation in the kidney, commonly seen in acute glomerulonephritis and pyelonephritis. When chronic glomerulonephritis is advanced, renal insufficiency or renal amyloidosis, the cellular tubular pattern stays in the renal tubules for a long time, or amyloidosis of renal tubular epithelial cells lyses, and wax-like tubular pattern may appear, suggesting serious damage to the renal tubules. In lipid nephropathy, fat droplets enter the tubular matrix and a “fatty tubular pattern” containing a large number of fat droplets can be seen. ②Cellular composition: the cellular composition of the urine sediment examination, in addition to red blood cells, there are white blood cells, epithelial cells. Normal centrifugal urine has no more than 5 leukocytes per high-powered field of view, and when the urine is alkaline, the leukocytes are easily destroyed, which should be noted during the examination. When the morphology of leukocytes is changed and the cells contain many granules and the internal structure is not clear, it is called “pus cells”. When there are a large number of leukocytes in the urine, it indicates urinary tract infections such as pyelonephritis, urethritis, cystitis, glomerulonephritis, interstitial inflammation, tumors, and inflammation of tissues adjacent to the urinary tract, or when women’s leukorrhea contaminates the urine, an abnormal number of leukocytes can be seen in the urine. A small number of epithelial cells can also be found in normal urine, and when there is a lesion in the urinary system, a large number of epithelial cells can appear, and the location of the lesion can be determined according to its different morphology. For example, small round epithelial cells are more common in renal tubular lesions; caudate epithelial cells are seen in renal pelvis, ureter and bladder neck lesions; flat epithelial cells (squamous epithelial cells) can increase in bladder and urethra lesions. In order to more accurately quantify the cellular component of the urine sediment, there are currently more methods, such as cell count per cubic millimeter of urine and 1-hour white blood cell excretion rate count. The most commonly used method is the Addison’s count (12-hour urine cell count), which determines the cellular composition and tubular pattern in 12-hour concentrated urine at night. Normal Edy’s count of red blood cells is 0 to 500,000; white blood cells should be less than 1 million; clear tubular type less than 5000. ③ Crystallization: crystallization in urine is related to the PH value of urine, check whether there are crystals in urine and their nature, mainly for the diagnosis of urinary stones has some significance. 4, urine sugar: there is only a trace of glucose in normal urine, the qualitative test is negative, and the 24-hour urine sugar quantification is between 10O and 900 mg. Increased urine sugar in kidney disease is mainly caused by damaged renal tubules, reduced reabsorption of sugar and decreased renal sugar threshold. When nephritis patients undergo urinalysis, the precautions for urine retention are: it is best to retain morning urine, because the morning urine is more concentrated and contains more pathological components; the container used for urine retention must be cleaned beforehand to ensure that the urine is clean and clean; female patients should pay particular attention to prevent contamination by vaginal secretions or menstrual blood; it is best to send urine for testing immediately after retention, if more than one hour to send for testing, it should be refrigerated at low temperature or selected with preservatives as appropriate In special cases, urine specimens should be taken according to special requirements in strict compliance with medical advice.