Serum urea is a metabolite of protein's disease, which is excreted with urine mainly through glomerular filtration. When the renal parenchyma is damaged, the glomerular filtration rate decreases, which leads to the increase of serum urea concentration in blood. Therefore, the filtration function of glomerulus can be understood by measuring urea.
Extended data:
1, serum urea increased.
(1) Chronic nephritis, severe pyelonephritis, etc. When renal function is slightly impaired, the detection value of urea may not change. When this value is higher than the normal value, it means that more than 50% of the effective nephron has been damaged. Therefore, the determination of urea can not be used as an index of renal function in early stage of nephropathy, but it is of special value in the diagnosis of renal failure, especially in azotemia.
(2) Urinary system diseases, urinary calculi, tumors, prostatic hyperplasia, prostate diseases, etc. When urine volume is obviously reduced or urinary tract obstruction causes urinary atresia, it can also cause serum urea to increase.
(3) Other high-protein diets, dehydration, increased protein catabolism, ascites, edema, biliary tract surgery, upper gastrointestinal bleeding, women in the third trimester of pregnancy, phosphorus and arsenic poisoning, etc. The decrease of cardiac output or renal perfusion secondary to blood loss or other reasons will cause the increase of BUN.
2. Decreased serum urea
It is found in toxic hepatitis, acute liver atrophy and lipid-like nephropathy.
(2) Serum creatinine
Serum creatinine concentration can accurately reflect the damage degree of glomerular filtration function to some extent. When the renal function is normal, the creatinine excretion rate is constant, and when the renal parenchyma is damaged, the glomerular filtration rate will decrease. When the filtration rate drops to a certain extent, the serum creatinine concentration will rise sharply.
1, increase
The increase of serum creatinine is mainly seen in acute and chronic glomerulonephritis and other kidney diseases. In early or mild renal function damage, due to the strong reserve and compensatory ability of the kidney, the blood creatinine concentration can be normal, and when the glomerular filtration function drops to 30% ~ 50%, the blood creatinine value will increase obviously.
When the renal blood flow is normal, the serum creatinine is 176 ~ 355 μ mol/L, which indicates moderate and severe renal damage. If serum creatinine and urea increase at the same time, it means that renal function is seriously damaged.
Step 2 reduce
It is found in progressive muscular atrophy, leukemia, anemia, liver dysfunction and pregnancy.
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