Isotonic urine (urine concentration and dilution function is reduced): CRF (chronic renal failure) early renal function is reduced while dilution function is normal, with the aggravation of the disease, the kidney dilution function is also impaired, so that the final urine osmolality is close to plasma, urine specific gravity is often fixed at 1.008-1.012, called isotonic urine. The following tests must also be done to help diagnose and differential diagnosis. 1, urine specific gravity: urine specific gravity meter is used to determine. 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. Urine specific gravity is proportional to the amount of solutes contained in the 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. 2, urine acidity and alkalinity (pH): commonly used pH test paper or pH meter to determine. Normal urine is generally weakly acidic, pH 6.5 or so, due to the influence of diet and so on, sometimes can be neutral or weakly alkaline. Acidic or alkaline urine can occur in the presence of disease or medication. When the renal tubular acidosis, although the acidosis is very serious, but the urine pH value does not correspondingly lower, which is important for the 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 amount of tubular type 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. ② Cellular component: The cellular component of the urine sediment examination is not only red blood cells, but also white blood cells and epithelial cells. Normal centrifugal urine has no more than 5 leukocytes per high-powered field of view. 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 particles and the internal structure is not clear, it is called “pus cells”. (3) Crystals: Crystals in urine are related to the PH value of urine. Checking whether there are crystals in urine and their nature is mainly significant for the diagnosis of urinary stones. 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 urinalysis is performed in patients with nephritis, the precautions for urine retention are: it is best to retain morning urine because it is more concentrated and contains more pathological components; the container used for urine retention must be cleaned beforehand to ensure the cleanliness and cleanliness of the urine; 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, and if it takes more than one hour to send for testing, it should be refrigerated at low temperature or preservatives should be added as appropriate In special cases, urine specimens should be taken according to special requirements in strict compliance with medical advice.