serum urea

Urea (ure) is the end product of mammalian protein catabolism. It is synthesized in the liver by ornithine and is mainly excreted by the kidneys. Because urea has a small molecular weight and is easy to dissolve, and the diffusion force is extremely large, the concentrations of urea in cerebrospinal fluid, serosal effusion, saliva, and sweat are basically the same. Blood urea concentration is mainly affected by renal function and protein intake and catabolism. At present, the most commonly used methods for determining urea in clinical laboratories are diacetyl-hydrazine method and enzyme coupling rate method. Basic Information Specialist classification: urinary examination classification: blood examination Applicable gender: whether men and women apply fasting: fasting Analysis results: Below normal: Less common in clinical practice. Mainly due to damage to the liver parenchyma, reduced production. Such as acute yellow liver atrophy, cirrhosis, toxic hepatitis, severe anemia. Normal value: Serum urea: 2.0-7.1mmol/L Above normal: 1, kidney disease such as acute renal failure, chronic nephritis, renal arteriosclerosis, chronic pyelonephritis, kidney tuberculosis, kidney tumor, etc., mild renal impairment, BUN can be unchanged. BUN increased when 60% to 70% of the effective nephron was damaged. Therefore, BUN measurement can not be used as an indicator of early impaired renal function, but it has special value for the diagnosis of renal failure, especially uremia, and can judge the condition and estimate the prognosis. The degree of renal failure can be judged based on the BUN measurement results. A. Renal failure compensated Ccr decreased, blood Cr was normal. BUN was normal or slightly elevated (9 mmol/L). C. Ccr 445 μmol/L in uremic phase, BUN>20 mmol/L. 2, pre-renal or post-renal factors cause significant reduction in urine output or urinary closure, such as severe vomiting, diarrhea caused by dehydration, edema, ascites, circulatory failure, as well as urinary tract stones, prostatic hypertrophy, tumors, etc. obstruction. 3, excessive protein decomposition in the body, such as large area burns, major surgery, upper gastrointestinal bleeding, hyperthyroidism and acute infectious diseases. At this time, BUN increased, while other renal function tests were generally normal. negative: Positive: Reminder: The reagent cup, sample cup and reaction cup should be free of ammonia, clean and free from acid and alkali pollution. Normal value 1. Diacetyl-hydrazine method 2.0 to 7.1 mmol/L. 2. The enzyme coupling rate method is 2.0 to 7.1 mmol/L. Clinical significance 1. Increase: (1) Kidney diseases such as acute renal failure, chronic nephritis, renal arteriosclerosis, chronic pyelonephritis, renal tuberculosis, advanced renal tumors, etc., when renal function is slightly impaired, BUN may be unchanged. BUN increased when 60% to 70% of the effective nephron was damaged. Therefore, BUN measurement can not be used as an indicator of early impaired renal function, but it has special value for the diagnosis of renal failure, especially uremia, and can judge the condition and estimate the prognosis. The degree of renal failure can be judged based on the BUN measurement results. A. Renal failure compensated Ccr decreased, blood Cr was normal. BUN is normal or slightly elevated (<9 mol/L). B. Decompensation of renal failure (nitrogenemia or uremia) Ccr decreased significantly (<0.83ml/s), blood Cr increased (>90mmol/L), BUN moderately increased (>9mmol/ L). C. Ccr<0.33ml/s in uremic phase, blood Cr>445μmol/L, BUN>20mmol/L. (2) Pre-renal or post-renal factors cause significant reduction in urine output or urinary closure, such as severe vomiting, dehydration caused by diarrhea, edema, ascites, circulatory failure, and urinary calculi, prostatic hypertrophy, tumors, etc. Road obstruction. (3) Excessive protein decomposition in the body, such as large area burns, major surgery, upper gastrointestinal bleeding, hyperthyroidism and acute infectious diseases. At this time, BUN increased, while other renal function tests were generally normal. 2, lower: clinically less common. Mainly due to damage to the liver parenchyma, reduced production. Such as acute yellow liver atrophy, cirrhosis, toxic hepatitis, severe anemia. High results may be diseases: uremia, renal failure precautions 1, diacetyl-oxime method: (1) Urea cannot directly react with diacetyl-hydrazine, and the purpose of adding diacetyl-hydrazine and strong acid is to generate diacetyl which can be reacted therewith. The addition of Fe3+ (or Cd2+) is to eliminate the interference of hydroxylamine formed during the reaction, and the thiourea can increase the sensitivity of the reaction by 20 times. The method introduced in many previous books is to combine diacetyl-hydrazine with thiosemicarbazide. However, both can form a needle-like yellow substance, which is overcome by the use of thiourea in an acid reagent. (2) The acid concentration is positively correlated with the absorbance, so the acid concentration should be accurate. The diameter of the test tube used should be as uniform as possible in the boiling water. The liquid level should be above the liquid level in the test tube, and the boiling time should be put into the test tube to re-boiling. It is best to measure the standard and quality control each time. When observing the dynamic changes of urea, patients should be kept constant in protein intake and blood was collected on an empty stomach. When the sample cannot be analyzed immediately, the serum (or plasma) can be extracted into a sealed sample cup and stored at 4 ° C for 7 days. When the result is greater than 20 mmol/L, the sample is changed to 10 μl and the result is multiplied by 2. (3) Although this method adds thiosemicarbazide and cadmium ions, it enhances the color development intensity and color stability to a certain extent, but there is still fading (about 5% per hour), so after boiling heating and color cooling, Should be timely color comparison. (4) The 20μl sampler used must be corrected before use. (5) Plasma (clear) uric acid, creatinine, amino acids and other nitrogen-containing substances have no interference to this test, hemolysis may result in high results, and jaundice may result in low results. (6) Plasma (clear) urea content is closely related to the protein content of the food. In high-protein diets, the amount of urea in plasma (clear) can be significantly increased, while in low-protein diets, the content is significantly reduced. 2. Enzyme coupling rate method: (1) The most common problem with this method is the failure of the reagent or the contamination of the reaction system. The most unstable of the reagents are NADH and glutamate dehydrogenase. In the analysis process, attention should be paid to the following aspects: if plasma is used, fluorochemical compounds or NH4+ anticoagulants cannot be used. The former can inhibit urease activity, while the latter can participate in the reaction. (2) The reagent blank absorbance should be greater than 1.2A, otherwise the NADH is oxidized. For the same reagents and instruments, the F value should be relatively constant under the condition that the analysis conditions are constant, otherwise the reagent will be invalid. (3) Do not shake the reconstituted reagent to avoid deactivation of the enzyme. The reagent must be reconstituted with no ammonia. The reagent cup, sample cup and reaction cup should be free of ammonia, clean, and free of acid and alkali pollution. It should be calibrated each time and tested with quality control serum. Inspection process Diacetyl-hydrazine method: 1. The test tube is marked with a blank tube "B", a measuring tube "U", and a standard tube "S". 2, respectively, in the measuring tube plus plasma (clear) 20μl, standard tube plus standard application solution 20μl, blank tube plus distilled water 20μl. 3. 3 ml of each acidic reagent and 3 ml of diacetyl-hydrazine reagent. 4. Mix thoroughly, boil for 10 minutes, remove and cool. 5, 520nm wavelength, blank tube to zero colorimetric, read standard tube and measuring tube absorbance. Note: 1. Urea cannot directly react with diacetyl-hydrazine. The purpose of adding diacetyl-hydrazine and strong acid is to generate diacetyl which can react with it. The addition of Fe3+ (or Cd2+) is to eliminate the interference of hydroxylamine formed during the reaction, and the thiourea can increase the sensitivity of the reaction by 20 times. The method introduced in many previous books is to combine diacetyl-hydrazine with thiosemicarbazide. However, both can form a needle-like yellow substance, which is overcome by the use of thiourea in an acid reagent. 2. The acid concentration is positively correlated with the absorbance, so the acid concentration should be accurate. The diameter of the test tube used should be as uniform as possible in the boiling water. The liquid level should be above the liquid level in the test tube, and the boiling time should be put into the test tube to re-boiling. It is best to measure the standard and quality control each time. When observing the dynamic changes of urea, patients should be kept constant in protein intake and blood was collected on an empty stomach. When the sample cannot be analyzed immediately, the serum (or plasma) can be extracted into a sealed sample cup and stored at 4 ° C for 7 days. When the result is greater than 20 mmol/L, the sample is changed to 10 μl and the result is multiplied by 2. 3. Although this method adds thiosemicarbazide and cadmium ions, it enhances the color development intensity and color stability to a certain extent, but there is still fading (about 5% per hour). Therefore, after boiling heating and color cooling, Timely color comparison. 4. The 20μl sampler used must be corrected before use. 5. Plasma (clear) uric acid, creatinine, amino acids and other nitrogenous substances have no interference to this test, hemolysis may result in high results, and jaundice may result in low results. 6. Plasma (clear) urea content is closely related to the protein content of the food. In high-protein diets, the amount of urea in plasma (clear) can be significantly increased, while in low-protein diets, the content is significantly reduced. Enzyme coupling rate method: The reagent sample ratio was 70:1, 37 ° C, 340 nm, the lag time was 30 s, and the reading time was 30 s. The specific analysis conditions can be determined according to the specifications of the kit and the instrument, preferably every time. Note: 1. The most common problem with this method is the failure of the reagent or the contamination of the reaction system. The most unstable of the reagents are NADH and glutamate dehydrogenase. In the analysis process, attention should be paid to the following aspects: if plasma is used, fluorochemical compounds or NH4+ anticoagulants cannot be used. The former can inhibit urease activity, while the latter can participate in the reaction. 2. The absorbance of the reagent blank should be greater than 1.2A, otherwise the NADH is oxidized. For the same reagents and instruments, the F value should be relatively constant under the condition that the analysis conditions are constant, otherwise the reagent will be invalid. 3. Do not vibrate the reconstituted reagent to avoid deactivation of the enzyme. The reagent must be reconstituted with no ammonia. The reagent cup, sample cup and reaction cup should be free of ammonia, clean, and free of acid and alkali pollution. It should be calibrated each time and tested with quality control serum. Not suitable for the crowd Generally no taboos. Adverse reactions and risks Generally no taboos.