Evaluation of Liver Injury Mark J. Czaja Liver Research Center Albert Einstein College of Medicine Bronx, N.Y.

Liver Function Tests Alanine aminotransferase (ALT) Aspartate aminotransferase (AST) Lactate dehydrogenase (LDH) Alkaline phosphatase Bilirubin Albumin Really tests indicating injury and not necessarily function. Ideal test would be highly specific and sensitive. No test fulfills that criteria.

Mechanisms of Liver Dysfunction Direct cellular injury Blockage in bile flow Impaired blood flow

Direct Cellular Injury - HCV Infection

Blockage in Bile Flow - Biliary Atresia

Impaired Blood Flow - CHF

Consequences of Liver Injury liver cell injury liver cell death proliferation matrix deposition sufficient inadequate altered architecture recovery liver failure cirrhosis

Types of Liver Tests True tests of liver function Biochemical markers of liver injury Biochemical markers of specific liver diseases

Testable Biochemical Liver Function Ability to transport organic anions Capacity to metabolize certain substances Capability to synthesize various proteins

Steps in Organic Anion Transport Delivery and uptake Metabolic alteration Secretion and excretion

Bilirubin Tetrapyrole Toxic in neonates - kernicterus Derived from: Senescent RBC (70-80%) Hemoproteins (20-30%) Ineffective erythropoiesis

Bilirubin Formation heme biliverdin bilirubin oxygenase reductase Transport: hydrophobic due to internal H-bonding circulates bound to albumin

Bilirubin Metabolism Plasma Hepatocyte Bile Alb UCB UCB ligandin glucuronyl BMG BDG BMG BDG transferase BMG BDG

Bilirubin Elimination Intestine BMG (20%) + BDG (80%) +UCB (trace) Deconjugated to urobilinogen Excreted or reab-sorbed (20%) Urine BMG and BDG No UCB

Measurement of Serum Bilirubin Normal concentration < 1 mg/dl Conjugated < 5% Jaundice if > 3 mg/dl Detected by diazo reaction - cleaved to colored azo-dipyrole Conjugated reacts rapidly (direct) Unconjugated reacts slowly (indirect)

Differential Diagnosis I Prehepatic Intrahepatic Congenital Acquired Posthepatic

Differential Diagnosis II Unconjugated hyperbilirubinemia Increased bilirubin production (hematological) Decreased uptake (drug) Decreased conjugation (congenital) Conjugated hyperbilirubinemia Congenital Drug Liver disease Biliary obstruction

Inherited Disorders Causing Unconjugated Hyperbilirubinemia Crigler-Najjar syndrome Type 1 – absent GT Type 2 – reduced GT activity Gilbert’s syndrome – reduced GT activity due to genetic defect in TATAA element of GT promoter

Inherited Disorders Causing Conjugated Hyperbilirubinemia Dubin-Johnson syndrome – mutations in multidrug resistance associated protein 2 (MRP2) Rotor’s syndrome – genetic defect

Hepatic Metabolic Capacity Clearance must depend on total functional mass or metabolic activity Hepatic drug metabolism - [14C]amino-pyrine breath test Galactose elimination Not used clinically

Hepatic Synthetic Capacity Most major plasma proteins are made in the liver Decreased hepatocytes = decreased protein synthesis and release Albumin and coagulation factors are clinically important

Albumin 50% of all synthesized hepatic protein Determinant of plasma oncotic pressure Important transport protein

Serum Albumin Levels Long half-life of 20 days Large hepatic synthetic reserve Decreased with persistent, large injury Decreased in chronic liver disease Poor prognostic sign

Non-hepatic Causes of Hypoalbuminemia Severe malnutrition Renal or GI loss Glomerulopathy, HIV enteropathy High catabolism Infections, burns

Coagulation Factors Half-lives of hours to days Liver synthesizes I, II, V, VII, IX, and X Large synthetic reserve

Prothrombin Time (PT) PT detects abnormalities in I, II, V, VII and X (extrinsic pathway) PT is increased in liver disease Best prognostic indicator Acute liver disease Chronic liver disease

Non-hepatic Causes of Elevated PT Congenital coagulation factor deficiencies Consumptive coagulopathies Vitamin K deficiency (II, VII, IX, X)

To Rule Out Vitamin K Deficiency Any patient with an elevated PT Parental vitamin K for 3 days Normalization of PT - vitamin K deficiency Failure to normalize - hepatocellular disease

Serum Immunoglobulins Not produced by hepatocytes Frequently elevated in liver disease Secondary to inflammatory process ? produced by antigen shunting

Biochemical Markers of Liver Injury

Liver Enzymes Low levels always present in serum Leak out from cell after injury Very sensitive Magnitude of abnormality does not correlate well with degree of injury

Aspartate Aminotransferase (AST) Serum glutamic-oxaloacetic transaminase (SGOT) Transfers an a-amino group of aspartate to a-keto group of ketoglutaric acid Present in skeletal muscle, kidney, brain

Alanine Aminotransferase (ALT) Serum glutamic-pyruvic transaminase (SGPT) Transfers an a-amino group of alanine to a-keto group of ketoglutaric acid Present principally in liver

AST and ALT Elevated in most liver diseases Highest levels are in acute liver diseases Only slight elevations in chronic liver diseases Usually increase in parallel

AST/ALT in Alcoholic Hepatitis Transaminases rarely exceed 300 AST:ALT >2

Factors Affecting AST/ALT Depressed by pyridoxine (vit. B6) deficiency Decreased by uremia and renal dialysis

AST/ALT Controversies Should lower normal limits be used in females? Females < 30 vs. males < 40 Are the normal limits too high? Females < 20 and males < 30

Lactate Dehydrogenase (LDH) Component of classic LFT’s Highly non-specific

Tests of Impaired Hepatic Excretion Increased In Cholestasis Intra-hepatic biliary tract obstruction Extra-hepatic biliary obstruction

Alkaline Phosphatase Hydrolyzes phosphate esters at alkaline pH Also present in bone, kidney, placenta, intestine Mainly liver and bone in adults Increased in children from bone growth Placental form during pregnancy

Elevated Alkaline Phosphatase Can occur in any liver disease Highest with cholestasis or biliary tract obstruction Elevated in infiltrative diseases Due to increase synthesis and secretion

Alkaline Phosphatase Isoenzymes Source Heat Inactivation 5' NT GGTP Liver Moderate + Bone Rapid - Placenta Slow Intestine

5'-Nucleotidase Hydrolyzes 5'- adenosine monophosphate Mainly present in liver Increases along with alkaline phosphatase

g-Glutamyl Transpeptidase (GGTP) Transfers g-glutamyl groups Widely distributed Sensitive correlate to alkaline phosphatase Non-specific (alcoholism, MI, DM, pancreatic disease, renal failure)

Biochemical Markers of Specific Liver Diseases

Etiology-specific Liver Tests Viral hepatitis serologies Serum ferritin level Ceruloplasmin level Alpha1-antitrypsin level Antimitochondrial antibody titer

Viral Hepatitis Serology HAV – anti-HAV IgM and IgG HBV – HBsAg, anti-HBsAg, and anti-HBcAg HCV – anti-HCV, HCV RNA

Serum Ferritin Widely distributed storage protein Levels reflect body iron stores Elevated in primary hemochromatosis Elevated in acute inflammation and cirrhosis

Serum Ceruloplasmin Copper-binding protein Decreased in 95% of patients with Wilson’s disease 20% of heterozygotes have decreased levels

a1-Antitrypsin Inhibits serum trypsin Major component of a1-globulin Deficiency cause of neonatal hepatitis

Antimitochondrial Antibody (AMA) Directed against mitochondrial enzyme pyruvate dehydrogenase complex Positive in 90% of patients with primary biliary cirrhosis

Interpretation of Abnormal LFT’s Examine multiple tests Consider non-hepatic causes Determine the most abnormal tests

Hepatocellular vs. Cholestatic Test Hepatocellular Cholestatic ALT/AST 2-3 NL-1 Alk Phos Bilirubin NL-3 Albumin NL PT

Case 1 25 yo IVDA c/o 1 week of nausea, vomiting, and myalgias. Physical exam revealed jaundice. ALT 2045 (15-45) AST 2300 (15-45) Alk Phos 273 (50-150) Bili 3.9 (0.1-1.0) Alb 4.2 (3.5-5.5) PT 11.5 (10-12)

Hepatocellular W/U H & P EtOH, medications, transfusions Risk for viral hepatitis Risk factors for NASH Autoimmune features Etiology-specific LFT’s USG and liver biopsy

HBV Infection - HBcAg Staining

Case 2 67 yo c/o several months of weight loss, and 1 week of nausea, vomiting, and myalgias. Physical exam revealed cachexia and jaundice. ALT 75 (15-45) AST 115 (15-45) Alk Phos 650 (50-150) Bili 10.2 (0.1-1.0) Alb 4.2 (3.5-5.5) PT 11.0 (10-12)

medications, gallstones, weight loss Cholestatic W/U H & P medications, gallstones, weight loss USG normal dilated ducts AMA ERCP liver biopsy

Pancreatic Carcinoma - ERCP