What Is a Kidney Function Test?

The kidney is one of the most important organs in the human body. Its function is mainly to secrete and excrete urine, waste, poisons and drugs; regulate and maintain the volume and composition of body fluids (moisture and osmotic pressure, electrolytes, pH); maintain the internal environment (blood pressure , Endocrine). The glomerular filtered plasma is about 180L per day.

Basic Information

Chinese name: Renal function test
Foreign name: renal function tests

Instrument: Urine microscope
Set item: Urine sample, urine specific gravity, urine sediment microscopy

Clinical significance of renal function test

Clinical indicators commonly used to check renal function are serum urea, blood creatinine, blood 2-microglobulin, and uric acid.

(1) Serum urea (BUN)

Serum urea is a metabolite of human protein. It is mainly filtered through the glomerulus and excreted with the urine. When the renal parenchyma is damaged, the glomerular filtration rate decreases, resulting in an increase in serum urea concentration in the blood. Urea can understand the filtering function of glomeruli.

1. Increased serum urea

(1) Kidney disease Chronic nephritis, severe pyelonephritis, etc. When the renal function is slightly impaired, the urea detection value may not change. When this value is higher than normal, more than 50% of the effective nephrons have been damaged. Therefore, the determination of urea cannot be used as an indicator of renal function in the early stages of nephropathy, but it has special value for the diagnosis of renal failure, especially for azotemia.

(2) Urinary tract stones, tumors, benign prostatic hyperplasia, and prostate diseases that cause urinary tract obstruction to cause a significant decrease in urine volume or urinary occlusion can also cause increased serum urea.

(3) Other high-protein diets, dehydration, increased protein catabolism, ascites, edema, post-biliary tract surgery, upper gastrointestinal bleeding, post-pregnancy women, chemical poisoning such as phosphorus, arsenic, etc., cardiac output decreases or secondary to blood loss Decreased renal perfusion caused by other causes can cause increased BUN.

2. Decreased serum urea

Found in toxic hepatitis, acute liver atrophy, lipidoid nephropathy and so on.

(B) blood creatinine

Serum creatinine concentration can accurately reflect the degree of damage to glomerular filtration function to a certain extent. When the renal function is normal, the creatinine excretion rate is constant. When the renal parenchyma is damaged, the glomerular filtration rate will decrease. When the filtration rate is reduced to a certain level, the serum creatinine concentration will rise sharply.

Increase

Increased serum creatinine is mainly seen in renal diseases such as acute and chronic glomerulonephritis. In early or mild renal impairment, the serum creatinine concentration can be normal due to the strong reserve and compensatory capacity of the kidney. When the glomerular filtration function drops to 30% to 50%, the serum creatinine value becomes obvious rise. Under normal renal blood flow conditions, a serum creatinine of 176 to 355 mol / L indicates moderate to severe renal damage. If serum creatinine and urea are increased at the same time, it indicates that renal damage is very serious.

2. lower

Found in progressive muscle atrophy, leukemia, anemia, liver dysfunction, and pregnancy.

(Three) blood 2-microglobulin

Blood 2-microglobulin is a small molecule protein produced by lymphocytes, platelets, and polymorphonuclear leukocytes, and most of it is absorbed in the proximal tubules. Increases are seen in:

Renal dysfunction

Such as various acute or chronic nephritis, renal failure, diabetic nephropathy, kidney tumors, renal transplant rejection and so on. It is more sensitive than serum creatinine in assessing glomerular filtration function.

Malignant tumor

Primary liver cancer, lung cancer, gastric cancer, multiple myeloma, malignant lymphoma, etc.

3. Autoimmune diseases

Systemic lupus erythematosus, rheumatoid arthritis, autoimmune hemolytic anemia, etc.

(D) Uric acid

Uric acid is the end product of purine metabolism in the body. Excreted mainly by the kidneys, so measuring uric acid can understand the function of the kidneys. Increases are seen in:

Gout

Elevated serum uric acid is the main basis for the diagnosis of gout.

Kidney disease

Acute or chronic nephritis, pyelonephritis, and renal tuberculosis can increase serum uric acid.

3. Malignant tumor

Various malignancies can cause elevated serum uric acid.