Biochemical examination refers to the use of biochemical methods to inspect the body. Because each indicator does not necessarily have visceral specificity, and some enzymes also have multiple isoenzymes, single indicators or a few indicators cannot clarify the pathogenic organ. If we can correctly and comprehensively interpret biochemical indicators, we can understand some of the conditions of organs such as the liver, kidney, heart, pancreas, gastrointestinal tract, urethra, pancreas, islets, thyroid, parathyroid, adrenal, pituitary gland, etc., and help judge the status of the body such as nutrition, immunity, dehydration, etc. However, to draw a more accurate conclusion on the disease, multiple clinical examinations are also required.
Hepatic physiological function
1. Secretion and excretion: Bile acid is the main component in bile and is the final product of cholesterol metabolism through the liver. Total bile acid is the most sensitive liver function program. The vast majority of cholesterol and triglycerides are synthesized by the liver. Liver diseases affect ammonia synthesis and urea also cause blood ammonia to rise.
2. Liver enzyme metabolism: ALT has liver-specific injury, and high ALT and AST are both corresponding to hepatocyte damage. AST higher than ALT indicates muscle damage. High ALP, CHE, and LDH correspond to suggest biliary obstruction. Increased GLOB is largely related to liver tumors and is a sign of whether liver inflammation returns to normal.
3. Protein metabolism: mainly detects total protein, albumin, globulin, and white ball ratio. Low albumin and total protein can indicate chronic liver disease. White ball ratio inversion is seen in liver injury. The liver is the only place to synthesize albumin, which maintains colloidal osmotic pressure.
4. Lipid metabolism: Hepatocytes secrete bile metabolize lipids including cholesterol and triglycerides.
5. Carbohydrate metabolism: The liver synthesizes sugar into glycogen and stores it, and converts excessive sugar into fat. The liver function maintains blood sugar levels when it is hungry, and acute liver problems can be considered when it is low.
6. Bilirubin: The liver secretes bilirubin into bile, forming part of the bile. High bilirubin indicates that the liver's clearance ability is reduced, and excessive high suggests jaundice.
Renal physiological functions
1. Generate and excrete metabolites in urine: the renal tubules absorb substances such as glucose and excrete toxic substances such as creatinine, urea, and uric acid.
2. Regulate acid-base balance: The body will produce a large amount of acidic substances and a small amount of alkaline substances in the process of decomposing sugars, proteins and fats, expel H ions, and repeat the synthesize to absorb HCO3 ions, adjust acid-base balance and pH changes.
3. Regulating electrolytes: The glomerular filtration solution contains a variety of electrolytes. After entering the renal tubules, most of the sodium, potassium, calcium, magnesium, chloride ions, phosphate ions, bicarbonate ions, etc. are reabsorbed.
4. Secrete hormones: secrete renin, etc.
Physiologic of calcium and phosphorus
1. Osteogenic function: The vast majority of calcium and phosphorus are found in bones and teeth, and play a supporting and protective role.
2. Coagulation: Calcium and phosphorus participate in the coagulation process.
3. Calcium is involved in the coupling factor between nerve excitation and muscle contraction, controlling muscle contraction and diastolicity. When normal, calcium is stored outside the cells, and when cells are excited, calcium enters the cells. When the calcium concentration is low, the neuromuscle intelligently contracts and then twitches.
4. Calcium regulates enzyme activity, and calcium can promote the activity of certain enzymes
5. Phosphorus is an important component of important proteins and enzymes, and participates in energy metabolism.
Endocrine and Biochemistry
1. Thyroid: The thyroid degrades in the liver to form glucuronic acid or carbonate. Hypothyroidism occurs simultaneously with diabetes, and hypothyroidism occurs simultaneously with Addison's disease, which can be seen as hypercholesterolemia.
2. Parathyroid gland: Secretion is affected by blood calcium. Continuous high calcium and low phosphorus or normal can indicate hyperactivity.
3. Pancreas: It has both endocrine and exocrine functions. The pancreas is the place for endocrine pancreas, secreting insulin, insulin and glucagon jointly maintain blood sugar levels.
The interpretation significance of various important indicators
Alkaline transaminase ALT
ALT, as the name suggests, is an aminotransferase between glutamate and pyruvate, mainly found in the liver, heart and skeletal muscle. Damage or necrosis of liver cells or certain tissues can increase the alanine aminotransferase in the blood. There are many clinical diseases that can cause abnormal aminotransferase. There are many reasons for the elevated ALT, including acute soft tissue damage and severe trauma, strenuous exercise or excessive exercise, infectious diseases such as pneumonia, tuberculosis, heart disease such as heart failure, myocarditis, cholecystitis, and the use of some drugs. Therefore, when clinical biochemical examinations see mild increase in ALT, they should not only suspect liver problems, but should comprehensively consider the animal's condition and comprehensively analyze the test form.
Greena aminotransferase AST
AST is present in various tissue cells, and the content in muscle tissue is very high, and the content in cardiomyocytes is significantly higher than that in liver cells. Therefore, the significant increase in AST accompanied by CK (creatine kinase) often indicates skeletal muscle damage or heart disease. In addition, non-hepatic factors that can cause increased ALT can cause increased AST. Recently, it has been reported that large amounts of consumption of high animal fat can also cause increased ALT. There are two isoenzymes in the liver AST, which are present in the cytoplasm of hepatocytes (sAST) and in the mitochondria of hepatocytes (mAST). Therefore, when the liver is slightly damaged, the liver cells only rupture the cytoplasm, and the ALT and sAST in the cytoplasm enter the blood, causing the serum ALT and AST to basically increase in the same proportion at the same time. When the liver is severely damaged, the mitochondria of the cell ruptures and mAST is released into the blood. At this time, the AST value in the serum is the sum of sAST and mAST. Therefore, the proportion of AST increase is higher than that of ALT. The higher the proportion of the increase, the more severe the degree of liver damage is, the more serious the degree of liver damage is..
Total bilirubin TBIL
BIL is the sum of direct bilirubin and indirect bilirubin. The bilirubin in normal serum is basically derived from the hemoglobin produced after the breaking of aging red blood cells. The glucuronated in the liver is called direct bilirubin, and the glucuronated in the liver is called indirect bilirubin. The causes of elevated total bilirubin include hemolytic diseases and microbial infections that cause excessive indirect bilirubin, which is not too late to convert it into direct bilirubin and bile by the liver, which causes direct bilirubin to rise simply due to indirect bilirubin. In liver disease, bilirubin cannot be converted into bile or cholestasis in the liver caused by swelling of hepatocytes, causing simultaneous increase of straight and intercollectal gallbladder, resulting in hepatocyte jaundice. When cholecystitis or general bile duct obstruction occurs, bile is discharged into the duodenal disorder, causing obstructive jaundice.
Due to the different lengths of hairs and skin color of dogs and cats, clinically, it is generally judged by the color observation of the ocular conjunctiva, transient membrane and oral mucosa. Generally, jaundice below 30mmol/L should not be detected by the naked eye, which is called recessive jaundice. When hindered jaundice is suspected, it can be judged through urine test. When mild hemolysis occurs, the liver's ability to convert interbirth into straight bile can be enhanced within a certain range, so the serum bilirubin level will not increase at this time. However, when moderate to severe hemolysis occurs, a large number of red blood cells break down leads to excessive indirect bilirubin entering the serum, and the liver does not have time to transform, resulting in a mild and moderate increase in serum total bilirubin levels. Elichinite and Mycoplasma infections in dogs, and infectious peritonitis in cats can also cause prehepatic jaundice.
Lactate Dehydrogenase LDH
LDH is a glycolytic enzyme that is present in the cytoplasm of almost all tissue cells, catalyzing the mutual conversion of lactic acid and pyruvate. During anaerobic fermentation, catalytic pyruvate accepts hydrogen formed by glyceraldehyde 3-phosphate dehydrogenase to form lactic acid. LDH is composed of five isoenzymes, and the isoenzyme distribution has obvious tissue specificity, so it can assist in the diagnosis of diseases based on its tissue specificity. At present, domestic veterinary medicine has not yet conducted clinical use of electrophoresis or enzyme-linked immunoassay to determine isoenzymes. Since LDH is present in almost all cells and is generally highly active in body tissues, the increase in serum LDH is nonspecific for any single tissue or organ and has no clear diagnostic significance.
Alkaline phosphatase ALP
ALP is composed of 6 isoenzymes and is widely present in various tissues of the body. It is present in the liver, kidney, bone, intestine, placenta and certain tumor tissues, but it is mainly found in the liver and bones. During the skeletal development, fracture healing and pregnancy period in dogs and cats, mild physiological increase in ALP can be caused. Osteomyelitis, rickets, osteoporosis, bone tumor, liver abscess, cirrhosis, liver tumor, and hyperthyroidism. During extrahepatic biliary tract obstruction, gallbladder disease, and cholestasis hepatitis, hepatocytes overproduce ALP and enter the blood through the lymphatic tract and liver sinusoids. At the same time, due to bile excretion disorders, it refluxes into the blood, causing a significant increase in serum ALP.
In the clinical practice of dogs and cats, the clinical significance suggested by elevated ALP is not exactly the same. In dogs, hepatic disease, Kushing's syndrome, glucocorticoids or antiepileptic medications are indicated. In cats, it is suggested that diabetes, cholangitis, cholangitis, hepatic lipidosis, hyperthyroidism, etc. ALP may drop slightly when dogs are hypothyroidism.
urea nitrogen BUN
BUN is produced by the metabolism of ammonia in the body in the liver and is mainly excreted from the body through the kidneys. BUN elevation is clinically called azotemia, and it is divided into three types: pre-renal, middle-renal, and posterior renal. Prerenal renal disease is found in congestive heart failure, high fever, shock, gastrointestinal bleeding, dehydration, severe infection, diabetic ketoacidosis, severe muscle damage, glucocorticoid or tetracycline, Atysen's disease, high protein diet, hepatorenal syndrome and other factors; renal neutral disease is common in renal dysfunction caused by acute nephritis, chronic interstitial nephritis, severe pyelonephritis, congenital polycystic kidney and renal tumors; postrenal renal disease is seen in urinary tract obstruction caused by various reasons, which reduces glomerular filtration pressure, and is common in urethral stones, dysparticle, constipation, prostate tumors, pelvic tumors, bilateral ureteral stones and other factors. Reduction of BUN in blood is common in excess water intake, too little protein intake, assimilating hormones that promote protein synthesis, and late pregnancy and severe liver diseases.
creatinine CREA
creatinine is a product of body muscle metabolism. In muscles, creatine is mainly slowly formed by irreversible non-enzymatic dehydration reactions, and is then released into the blood and excreted in the urine. Therefore, the amount of creatinine in the blood is closely related to the total amount of muscle in the body and is not easily affected by diet. Creatinine is a small molecule substance that can be filtered through the globulum and is rarely absorbed in the renal tubules. Almost all of the creatinine produced in the body is excreted in the urine. In normal times, it is generally not affected by the amount of urine. The main reason for the increase in creatinine is renal insufficiency. When renal function drops to 1/4-1/3 of the normal creatinine begins to rise. CREA in blood can also be increased during severe infection, strenuous exercise, excessive growth hormone, diabetes, and large-scale use of VitC. The reduction in creatinine is seen in late pregnancy, severe muscular dystrophy, severe congestive heart failure, and the use of androgens or thiazide diuretics.