第十章 肝胆疾病的生物化学诊断课件

肝胆疾病的生物化学检验 Biochemistry test of liver disease 1 了解： 肝脏的结构与血液供应特点、肝脏的主 要功能、胆红素的正常代谢通路。（第一节） 熟悉： 肝胆疾病的代谢紊乱。常用肝功能试验 的选择及组合（第三节部分和第四节） 掌握： 肝胆疾病的常用生物化学检验、肝胆疾 病的实验诊断。（第二节和第三节部分） 2 第一节 肝胆的结构及功能概述 Structure and functions of the liver 一、肝脏的结构 Structure of the liver 二、肝脏的功能 Functions of the liver 三、胆汁的生成及组成 production of the bile 胆红素代谢 Metabolism of bilirubin 3 4 Overview of the Liver / The liver is a vital organ located in the upper right-hand side of the abdomen. Somewhat larger than the size of a football and weighing about 2-3 pounds, it performs numerous functions for the body: converting转化 nutrients营养素 derived from得到 food into essential基本的 blood components, storing vitamins and minerals, regulating blood clotting凝固, 5 producing proteins and enzymes, maintaining hormone balances, and metabolizing代谢 and detoxifying解毒 substances that would otherwise be harmful to the body. The liver also makes factors that help the human immune system fight infection, removes bacteria from the blood, and makes bile, which is essential for digestion. 6 Bile, a greenish-yellow fluid consisting of bile acids (or salts) and waste products废物 , such as bile pigments胆色素, flows through small bile ducts inside the liver. The bile moves from these small ducts into larger ones, like streams into a river, eventually traveling into the common bile duct and out of the liver. 7 Some of the bile flows directly to the duodenum十二指肠; the rest is stored and concentrated in the gallbladder胆囊. After a person eats, the gallbladder, a fist拳-sized organ that sits next to the liver, releases some of the stored bile into the small intestine小肠, where it helps to digest fats. 8 一、肝脏的结构与 血液供应特点 双重血液供应 微绒毛多 丰富的亚细胞结 构 众多的酶系9 入： 双重血液供应(Double blood supply) 门静脉(Portal vein) : 60% 肝动脉(Hepatic artery): 40% , 70% 氧 出： 总胆管 Common bile duct 肝静脉 Hepatic vein 10 微绒毛多 增大了与血窦的接触面 通透性高 有利于物质的转运 丰富的亚细胞结构 物质代谢的场所 线粒体；内质网；高尔基体；溶酶体 众多的酶系 物质代谢保障 11 二、肝脏物质代谢 (1) Metabolism of proteins, carbohydrates and lipids. (2) Synthesis and secrete bile acid (3) Biotransformation (生物转化) (4) Breakdown hormones(激素) 12 （一）蛋白质代谢(Protein metabolism) 肝脏作用： (1) 合成、分泌血浆蛋白质 (2) 转化、分解氨基酸 (3) 合成尿素(urea)清除氨(amonia) 13 肝功能障碍时： (1) Acute liver disease急性肝病 : albumin (A) ,globulin (G)变化不 大 (2) Chronic liver disease慢性肝病: Serum TP,A/G 14 (二）糖代谢 (Carbohydrate metabolism) 肝脏作用： (1) 糖原合成、分解 (2) 糖异生 (3) 糖转化脂类 15 空腹低血糖(hypoglycemia) : (1) 正常时: 血糖糖原分解,糖异生 血糖 (2) 肝功能障碍时: 肝细胞内葡萄糖-6-磷酸 酶等酶糖异生,糖原合成,肝内糖原储 备减少 血糖 16 (三）脂类代谢 (Lipid metabolism) TG： 肝内脂肪氧化障碍脂肪堆积脂 肪肝( fatty liver) 脂肪肝: 肝内脂类含量超过肝重的 5%时 17 （二） 肝脏的生物转化作用 Biotransformation of the liver 1.概念: 来自体内外的非营养物质在体内的种种 代谢转变过程，如灭活，增加水溶性，降低毒 性等。 18 2. 生物转化的类型 Phase I： Oxidation 氧化 Reduction 还原 Hydrolysis 水解 19 Phase II Conjugation 结合反应： Glucuronic acid葡萄糖醛酸 Sulfate 硫酸 Glutathion 谷胱甘肽 Glycine 甘氨酸 20 3. 意义 解毒与制毒双重性 药物的生物转化 (Biotransformation of drug) 灭活 活性不变 毒性增强 21 22 三 胆汁的生成与组成 和黄疸一起讲 23 Signs and Symptoms of liver disease Liver disease may not cause any symptoms at first or the symptoms may be vague不确切, like weakness and loss of energy. In acute liver disease, symptoms related to problems handling bilirubin, including jaundice, dark urine, and light stools稀粪便, along with loss of appetite食欲 , nausea恶心, vomiting呕吐, and diarrhea腹 泻are the most common. 24 Chronic liver disease symptoms may include jaundice, dark urine, abdominal swelling (due to ascites腹水), unexplained weight loss or gain, and abdominal pain; these symptoms may not be present until the disease has reached an advanced stage. 25 Testing Laboratory Tests Three types of tests are often used to detect liver disease; these tests either measure the levels of specific enzymes, bilirubin, or protein present in the test sample (usually a blood sample). Non-Laboratory Tests Computerized axial tomography (CAT) scan计算机控制(横)轴向(x线)断层(扫描 Ultrasound 26 Routine Liver function tests（LFTs） AST、ALT、ALP、GGT、 albumin、prealbumin、 prothrombin time凝血酶原时间、 bilirubin、bile acid等 27 Routine liver function tests Standard group of tests Property being assessed ALT,AST ALP,GGT Hepatocellular integrity Cholestasis Bilirubin Bile acid Metabolism Albumin Prothrombin time Protein synthesis 28 Enzymes: Enzymes are proteins that help cells do their work. When cells are injured, enzymes can leak into the blood at higher- than-normal levels. Some common enzymes used to detect liver disease are: 29 Alanine aminotransferase (ALT) - an enzyme found mainly in the liver; the best test for detecting hepatitis Alkaline phosphatase (ALP) - an enzyme related to the bile ducts; often increased when they are blocked Aspartate aminotransferase (AST) - an enzyme found in the liver and a few other places, particularly the heart and other muscles Gamma-glutamyl transferase (GGT) an enzyme found mainly in the liver; very sensitive to changes in liver function 30 1. The aminotransferases (AST and ALT) Soluble可溶的 cytoplasmic细胞质的 enzymes and mitochondrial 线粒体的 enzymes (e.g. ALT and AST ) are released into plasma in hepatocellular damage 31 Serum ALT measurements are more liver-specific than AST . AST has both cytoplasmic and mitochondrial线粒体的 isoenzymes，and tends to be released more than ALT in chronic hepatocellular disease(e.g.cirrhosis 肝硬化) 32 ALTASTAST/ALT 急性肝炎 慢性肝炎 肝硬化，肝 癌，酒精肝 胆汁淤积 AST 、ALT 的应用 诊断肝细胞损伤程度 33 2. ALP and GGT ALP and GGT tend to be released into plasma in only small amounts following hepatocellular damage However, they are released in much greater amounts when there is cholestasis 胆汁郁积 since their synthesis is induced. 34 Changes in the activities of GGT and ALP often parallel each other in cholestatic胆汁郁积的 liver disease Plasma GGT has the advantage of being more liver-specific，as plasma ALP may also be increased due to release from bone in bone disease. 35 ALP 、 GGT 的应用 诊断胆汁淤积。 GGT比ALP特异性好，但受酒精影响。 肝炎恢复期时，ALT和AST已经恢复正常后 ， GGT仍未降到正常。常作为患者是否可恢复 正常工作的标志。 36 肝胆疾病常用诊断酶 肝实质细实质细 胞损伤损伤ALT, AST LD ADA(腺苷脱氢氢酶) GD(谷氨酸脱氢氢酶) 胆汁淤积积GGT, ALP 5-NT(5核苷酸酶) 肝纤维纤维 化MAO(单单胺氧化酶) -PH(-脯氨酸羟羟化酶) 37 单胺氧化酶（MAO)：较早用于肝纤维化 诊断的项目。 MAO主要来自线粒体，其活性增高与体 内结缔组织增生密切相关。 80%肝硬化患者MAO增高。 如果肝癌患者MAO增高，表明该患者同 时伴有肝硬化。 38 Protein: One of the main functions of the liver is to make protein. Two important liver tests include: Albumin - measures the main protein made by the liver and tells how well the liver is making this protein Total Protein - measures albumin and all other proteins in blood, including antibodies made to help fight off infections (antibodies are not made in the liver) 39 (1) Total protein，albumin，A/G: In chronic hepatocellular damage, there is impaired albumin synthesis. Serum TP, albumin fall and A/G decrease provids a good index of the progress of the disease 为什么急性肝损伤时降低不明显？ The half-life of albumin is about 20 days and the clearance rate is low. 40 (2) Prothrombin time: In liver disease, the synthesis of prothrombin and other clotting factors(凝固 因子) is diminished减少，leading to an increased prothrombin time(PT). Vit K 缺乏亦可导致，如何区别？ In vitamin K deficiency, PT can be corrected by vitamin K，but this has no effect in hepatocellular damage 41 PT是反映肝脏合成功能、储备功能、病变严 重程度及预后的一个非常重要的指标。 在急性肝细胞疾病时，PT延长提示很可能发 生严重的肝损害。 慢性肝病时，PT延长也预示远期预后不良。 42 前清蛋白 PA;prealbumin 半衰期短，比清蛋白更敏感 胆碱酯酶 CHE;choline esterase 血清磷脂酰胆碱胆固醇酰基转移酶(LCAT) ：肝细胞损害时，LCAT合成减少，血清中 LCAT降低程度与肝损害严重程度相平行。比 清蛋白、胆碱酯酶敏感。 43 三、肝纤维化的生物化学检 验 肝纤维化（hepatic fibrosis） 是肝细胞发 生坏死及炎症刺激时，肝内纤维结缔组织弥 漫性异常增生的病理生理过程。肝纤维化是 慢性肝病重要的病理特征，是肝硬化发生的 必经中间环节，是一个缓慢而动态的过程。 早期肝纤维化尚有逆转至正常的可能，但进 入肝硬化阶段则往往被认为是不可复原的。 44 hepatic fibrosis Hepatic fibrosis is overly exuberant高度增 生的 wound healing创伤愈合 in which excessive connective tissue结缔组织 builds up in the liver. The extracellular matrix细胞 外基质 is either overproduced, degraded降 解 deficiently, or both. The trigger触发因素 is chronic injury, especially if there is an inflammatory component. 45 Fibrosis itself causes no symptoms but can lead to portal hypertension 门静脉高血 压 (the scarring瘢痕形成 distorts扭曲 blood flow through the liver) or cirrhosis肝硬化 (the failure to properly replace destroyed liver cells results in liver dysfunction). Diagnosis is based on liver biopsy活组织 检查. Treatment involves correcting the underlying潜在的 condition when possible. 46 Various types of chronic liver injury can cause fibrosis. 肝硬化的发病原因 Disorders and Drugs that Can Cause Hepatic Fibrosis Disorders with direct hepatic effects: Certain storage diseases and inborn errors of metabolism: Copper storage diseases (Wilsons disease) Galactosemia半乳糖血症 Glycogen storage diseases糖原沉积 病 hemochromatosis血色素沉着症 Tyrosinemia 酪氨酸血症 47 Disorders and Drugs that Can Cause Hepatic Fibrosis Disorders with direct hepatic effects: Congenital hepatic fibrosis先天性肝纤维变 性 Infections Bacterial (eg, brucellosis布(鲁)氏(杆) 菌) Parasitic (eg, echinococcosis棘球蚴 病,包虫病) Viral (eg, chronic hepatitis肝炎 B or C) 48 Disorders and Drugs that Can Cause Hepatic Fibrosis Disorders affecting hepatic blood flow Heart failure Hepatic veno-occlusive disease肝静脉梗 阻症 Portal vein thrombosis门静脉血栓形成 Drugs and chemicals Alcohol Aldomin甲基多巴，治疗高血压 CCl4，四氯化碳 49 Acute liver injury (eg, acute viral hepatitis A), even when fulminant暴发, does not necessarily distort扭曲 the scaffolding architecture棚架结构 and hence does not cause fibrosis, despite loss of hepatocytes 肝细胞. In its initial stages初期, hepatic fibrosis can regress复原 if the cause is reversible可逆的 (eg, with viral clearance). After months or years of chronic or repeated injury, fibrosis becomes permanent. 50 （二）肝纤维化病因 1. 病毒性肝炎：慢性病毒性乙型肝炎和丙型肝炎 是我国最常见的肝纤维化病因。 2. 慢性酒精中毒 ：在欧美国家酒精性肝纤维化 占全部肝纤维化的50%90%。发病机理主要是酒 精中间代谢产物乙醛对肝脏的直接损害。 3. 遗传和代谢疾病 ：如血色病、肝豆状核变性 、半乳糖血症、糖原贮积病等。 4. 化学毒物或药物 ：长期服用某些药物、反复 接触某些化学毒物均可引起中毒性肝炎，最后演变 为肝纤维化。 5. 其他 肝淤血、脂肪肝 51 （三） 肝纤维化的发病机制 1细胞因子 ：1）生长因子、白细胞介素-1和 肿瘤坏死因子激活窦周储脂细胞、纤维母细胞 合成和分泌胶原、非胶原糖蛋白和蛋白多糖等；2 ）抑制Kupffe细胞合成和分泌胶原酶。 2储脂细胞（FSC）: 激活的FSC 合成大量 胶原、蛋白多糖及各种非胶原糖蛋白；表达多种 细胞因子和生长因子，分泌 TIMP 3Kupffer细胞: 释放大量细胞因子活化FSC 及引起肝细胞损害 4肝窦内皮细胞及Ca2+ :肝窦内皮细胞释放各 种介质肝纤维化形成初期起重要作用。 肝细胞损伤细胞内Ca2+蓄积，细胞死亡。 52 （四）肝纤维化生物化学检验 1型前胶原肽: 增高代表型胶原合成代谢 旺盛，对肝纤维化的早期诊断有意义。 2型胶原: 反映肝纤维化的程度及活动度。 急性肝炎时，肝细胞虽严重受损，但无结缔组织增 生，故血清IV型胶原水平无明显增加。慢性肝炎、 肝硬化等患者血清IV型胶原水平增高。 3层连粘蛋白（laminin, Ln）: 反映肝窦的毛 细胞血管化和汇管区纤维化的程度。肝硬化时血清 Ln明显升高。恶性肿瘤和结缔组织病也升高。 4透明质酸（hyaluronic acid, HA) : 反映肝 纤维化的敏感指标，也是反映肝脏功能的损害程度 的指标。恶性肿瘤和结缔组织疾病等也升高。 53 四、高胆红素血症 Hyperbilirubinemia 54 Bilirubin Also known as: Total bilirubin; TBIL; Direct bilirubin; Conjugated bilirubin; Indirect bilirubin; Unconjugated bilirubin Formal name: Bilirubin Related tests: Liver panel; Gamma- glutamyl transferase; Alkaline phosphatase; Aspartate aminotransferase; Alanine aminotransferase; Hepatitis A; Hepatitis B; Hepatitis C 55 血红蛋白 血红素 胆绿素 胆红素 球蛋白 NADPH +H+ 胆红素 清蛋白 复合物 血液 胆红素 Y,Z蛋白 胆红素- Y,Z蛋白 葡萄糖醛酸 胆红素酯 胆素原 胆素 排泄 葡萄糖醛酸胆红素 胆红素 胆素原 尿 胆素 Fe NADPH+H+ CO O2 单核-巨噬细胞系统 UDPGA 肝 葡萄糖醛酸 胆素原 肠肝循环 肠 管 滑面内质网 56 10% 20% 结合胆红素 门静脉 重新吸收 胆素原 胆素排泄 80%90% 生理意义 胆红素可大部排出 胆素原的肠肝循环 Enterohepatic circulation 57 胆红素的代谢 Metabolism of bilirubin 每个环节出现问题都可引起高胆红素血症 1. Source: Old RBC(red blood cell) ：80% hemoglobin血红蛋白haem血红 素 breakdown The remaining 20 ： Other haem proteins (cytochromes 细胞色素, myoglobin肌红蛋白, peroxidases过氧化物酶, 等) Ineffective RBC(无效红细胞) 58 2. Synthesis Old RBC haem 微粒体血红素加氧酶 biliverdin胆绿素 胆绿素还原酶 bilirubin250-300 mg/d 59 3. Transportation Free bilirubin is insoluble in water 游离胆红素为脂溶性,可弥散通过细 胞膜或血脑屏障产生核黄疸(中枢神经)。 Bilirubin is carried in plasma bound to albumin 运输形式: 胆红素-清蛋白复合物 Unconjugated bilirubin (非结合胆红素,UCB) 水溶性, 限制了自由通过生物膜的能力。 Thus it is not filtered at the glomerulus 肾小球. 影响因素: 清蛋白含量, pH, 有机阴离子等 60 4. Intake of hepatocyte 肝细胞摄取 Membrane receptor Cytosol胞质 receptor: Y蛋白(主要), Z蛋白 SER 肝细胞 未结合胆红素- 清蛋白复合物 摄取障碍时, 高未 结合胆红素血症61 5. Transformation SER滑面内质网 尿苷二磷酸葡萄糖醛酸基转移酶 (UDP-glucuronyltansferase, UDPGT) 胆红素葡萄糖醛酸酯 conjugated bilirubin (结合胆红素 ,CB) UDPGT缺乏时, 高未结合胆红素血症。 62 6. Excretion 主动转运载体 conjugated bilirubin bile duct 肝细胞损伤时，排泄障碍，结合胆 红素逆流入血，引起高结合胆红素血症。 63 7. Further metabolism of bilirubin in intestinal tract肠道 conjugated bilirubin hydrolysis水解 unconjugated bilirubin degraded by bacterial action bilinogen胆素原 oxidized by air Choline胆素 64 黄疸 Jaundice 1. Definition of jaundice 黄疸的定义 Jaundice is a yellow discoloration of the skin or sclera(巩膜). Due to the bilirubin concentration in plasma is much greater than normal. 三黄：目黄，身黄，便黄 65 The concentration of STB 血清总胆红素浓度 34.2mol/L jaundice 34.2-171mol/L mild jaundice 171-342mol/L moderate jaundice 342mol/L severe jaundice 66 Skin 67 Sclera 68 Urine 69 未结合胆红素 (血浆) (肝脏) 摄取、结合 结合胆红素 排泄 肠道 高胆红素血症 (hyperbilirubinemia ) 黄疸( jaundice ) 70 黄疸的分类： (1) 按症状分：隐性黄疸 显性黄疸 (2) 按病因分：溶血性黄疸 肝细胞性黄疸 梗阻性黄疸 71 (3) 按病变部位分：肝前性黄疸 肝性黄疸 肝后性黄疸 (4) 按血中升高的胆红素类型分： 高未结合胆红素性黄疸 高结合胆红素性黄疸 72 （二）黄疸的发病机制 1溶血性黄疸 : 多种原因红细胞大量破坏 胆红素生成 超过了肝脏的处理能力血中未 结合胆红素升高。 73 2. 肝细胞性黄疸 1)肝细胞被破坏血中未结合胆红素的摄取 、结合和排泄能力发生障碍血中未结合胆红 素增多； 2) 肝细胞肿胀、毛细胆管阻塞、毛细胆管与 肝血窦直接相通部分结合胆红素反流入血 血中结合胆红素浓度升高。 74 3胆红素排泄障碍 : 胆汁排泄受阻结合 胆红素逆流入血血中结合胆红素升高。 75 三种类型黄疸的实验室鉴别诊断 类类型 血清 尿液 粪粪便颜颜色 结结合胆红红素 未结结合胆红红素 尿胆红红素 尿胆原 正常人无或极微 有 （） 少量 棕黄色 溶血性黄疸 （） 加深 肝细细胞性 黄疸 （+） 变变浅 梗阻性黄疸 （+） 变变浅或无 76 77 Jaundice Jaundice is a yellowing of the skin, whites of the eyes, and body fluids. It is caused by an increase in the amount of bilirubin in the blood. Bilirubin is a yellowish pigment浅黄色的色素 that is produced from the breakdown of heme, primarily from hemoglobin and red blood cells (RBCs). Bilirubin is transported by the blood to the liver, where the liver processes it, allowing it to be excreted in bile. 78 Bile is a thick稠的, yellow-green-brown fluid that is secreted into the upper small intestine to get rid of waste products (such as bilirubin and excess cholesterol) and to aid in the digestion of fats. Jaundice may arise from increased breakdown of red blood cells, inherited changes in bilirubin metabolism, liver disease or damage, and whenever there is interference with bile excretion. 79 Examples of common conditions that may cause jaundice Acute hepatitis Obstruction of the bile ducts inside and/or outside of the liver Hemolytic anemia 溶血性贫血 Cirrhosis 肝硬化 80 Physiologic jaundice of the newborn: the liver of a newborn infant has not fully developed its ability to metabolize bilirubin yet, so newborns frequently go through a brief period of jaundice right after they are born. Newborns with jaundice are carefully monitored and generally improve within 48 to 72 hours. If the jaundice persists or is severe, however, the infant may be treated and evaluated for other causes. 81 What does the test result mean of bilirubin? Newborns: Excessive bilirubin damages developing brain cells in infants (kernicterus) and may cause mental retardation智力迟钝, learning and developmental disabilities, hearing loss, or eye movement problems. It is important that bilirubin in newborns does not get too high. When the level of bilirubin is above a critical threshold, special treatments are initiated to lower it. 82 An excessive bilirubin level may result from the accelerated breakdown of red blood cells due to a blood type incompatibility血型不合 between the mother and her newborn (e.g., the mother is Rh-negative and has antibody to Rh-positive blood - the father is Rh-positive, and the fetus inherits this trait性状 from him; the mothers antibody crosses the placenta胎 盘 and causes the fetal Rh-positive red blood cells to hemolyze溶血, resulting in excessively elevated bilirubin levels with jaundice, anemia, and possible kernicterus脑核性黄疸.) 83 Adults and children: Bilirubin levels can be used to identify liver damage/disease or to monitor the progression of jaundice. Increased total or unconjugated bilirubin may be a result of hemolytic, sickle cell镰刀形红细 胞or pernicious anemias恶性贫血or a transfusion reaction输血反应. If conjugated bilirubin is elevated, there may be some kind of blockage of the liver or bile ducts, hepatitis, trauma to the liver, cirrhosis, a drug reaction, or long-term alcohol abuse. 84 Inherited disorders that cause abnormal bilirubin metabolism (Gilberts, Rotors, Dubin -Johnson, Crigler-Najjar syndromes) may also cause increased levels. Low levels of bilirubin are not generally a concern and are not monitored. 85 五、胆汁酸代谢 Metabolism of bile acid （一）胆汁酸正常代谢 胆汁酸是胆汁中存在的一类胆烷酸的总称。 1. 合成: 胆汁酸由胆固醇转变而来，是肝清除体内胆 固醇的主要方式。 肝脏合成初级胆汁酸：胆酸、鹅脱氧胆酸 肠道合成次级胆汁酸：脱氧胆酸、石胆酸 4种胆酸在胆汁中的比例通常为10:10:5:1 86 87 正常人每天体内合成胆固醇约1-1.5g，其中 约0.4-0.6g在肝内转变为胆汁酸。 胆汁酸在胆囊中储存浓缩5-10倍。进餐后， 胆囊在胰酶分泌素作用下发生收缩。在收缩过 程中，胆囊的作用像马达，驱动肠肝循环。进 餐消化后1-2小时内的血清胆汁酸水平比空腹时 大约高出两倍左右。 88 胆汁酸主要以结合型形式从肝分泌入肝汁。 结合型即指前述胆汁酸与甘氨酸或牛磺酸 结合而成的结合胆汁酸。 2. 功能: 促进脂类的消化吸收 调节胆固醇代谢 促进胆汁分泌 胆汁酸的分子内部既含亲水基团又含疏水基 团，能降低脂、水两相之间的表面张力，促进 脂类形成混合微团。 89 (95% 97%) 胆固醇 结合胆汁酸 (门静脉) 被动吸收 主动吸收 水解 脱羟 排泄 胆汁酸的肠肝循环 (0.40.6g/d) (合成0.40.6g/d) 3%5% 生理意义 胆汁酸可反复利用 每日需 1232g代谢池35g/d (胆道) 90 （二）胆汁酸异常 Abnormality of bile acid 1先天性疾病： 脑健性黄瘤病，合成酶缺乏， 血清胆汁酸降低。 2肝胆疾病：肝内胆汁淤积或门脉分流，胆汁 酸反流进入血，血清胆汁酸升高。 3肠道疾病 ：重吸收减少血清胆汁酸降低； 同时返回肝脏的胆汁酸减少负反馈加速胆汁酸合 成血清胆固醇浓度减低 。 4. 高脂血症：高脂蛋白血症时的代谢紊乱必然涉 及胆汁酸的代谢异常。 91 （三）胆汁酸生物化学检验 血清胆汁酸浓度很低（总胆汁酸2g/ml）， 可用气相色谱、放射免疫、高效液相层析法及 酶学分析法（以3-羟类胆固醇脱氢酶为工具酶 ）测定NADH生成量。 92 1 空腹血清TBA测定 主要用于肝细胞损害的诊断，其灵敏度和特 异性均高于其他指标，血清TBA。 胆道梗阻时胆汁酸排泄受阻，血清TBA。 门脉分流，肠道中次级胆酸经分流的门脉直 接进人体循环，使血清中TBA。 进食后血清胆汁酸可一过性增高，此为生理 现象。 93 2餐后2小时血清TBA测定 肝病时餐后血清胆汁酸升高较空腹时更明显 。 3血清胆酸鹅脱氧胆酸比值 CA/CDCA比值可作为肝实质病变与胆 汁淤积性病变的鉴别指标。 94 CA：胆酸 (3,7,12-三羟基胆汁酸 ) CDCA：鹅脱氧胆酸， (3,7-二羟基胆汁酸) 正常参考值： CA 10-100mg/L，CDCA 10- 80mg/L， CA/CDCA 0.5-1.0 肝硬化：CA/CDCA ，0.1-0.5 肝细胞损伤时， 12-羟化酶 ，CA合成 减少，而CDCA的合成不需该酶。 胆道梗阻： CA/CDCA ，1.0-3.6 胆道梗阻时，血清中CA和CDCA均增加 ，但CA所占比值较高使CA/CDCA比值大于1 。 95 六、肝胆疾病的其他生化检 验 自学 96 第三节 常见肝胆疾病的代谢紊乱及实 验诊断 一、急性肝炎 急性黄疸型肝炎多见于甲型肝炎和戊型肝 炎，病程的阶段性较为明显。 急性无黄疸型肝炎，属轻型肝炎，由于无 黄疸不易被发现，因而成为重要的传染源。 常见病因：肝炎病毒感染、药物及化学毒 物中毒、酒精。 97 急性肝炎的实验诊断 1血清酶 ALT、AST升高 2血清和尿胆色素 详见P177黄疸的实验室鉴别诊断 3凝血酶原时间 与肝损害程度呈正相关 。 4血氨浓度 血氨浓度升高提示肝性脑病 。 5其他实验室检查 肝炎病毒的免疫学和分子生物学检测 血常规检查 尿常规检查 98 二、慢性肝炎 慢性肝炎 病毒性肝炎病程持续一年（国外 半年）以上者即为慢性肝炎。 乙型肝炎占绝大多数（80）。 慢性持续性肝炎，半年以上，