LIVER FUNCTION TESTS http://crisbertcualteros.page.tl

2. Distinguish among the different types of liver diseases 1. Detect the presence of liver diseases 2. Distinguish among the different types of liver diseases 3. Gauge the extent of known liver damage 4. Follow response to treatment

Liver tests have shortcomings. They rarely suggest a specific diagnosis rather they suggest a general category of liver diseases, such as hepatocellular or cholestatic; which then further directs the evaluation..

AND EXCRETORY FUNCTIONS: TESTS BASED ON DETOXIFICATIONS AND EXCRETORY FUNCTIONS: 1. SERUM BILIRUBIN – a breakdown product of porphyrin ring of heme containing proteins (conjugated,unconjugated) unconjugated/indirect – insouble in water; bound to albumin in the blood conjugated/direct – water soluble; excreted in kidneys

Normal serum bilirubin concentration: <17 micromol/L (1mg/dl) Up to 30% of the total is direct-reacting

Elevation of unconjugated fraction of bilirubin: rarely due to liver disease hemolytic disorder genetic conditions: Crigler-Najjar, Gilbert Syndrome Elevation of conjugated bilirubin: almost always implies liver or biliary tract disease

2. URINE BILIRUBIN: presence of bilirubinuria  liver diseases  almost 100% accurate 3. BLOOD AMMONIA: elevated in advanced liver diseases with significant muscle wasting  Hyperammonimea There is a poor correlation between either the presence or the degree of acute enceph and elevation of blood ammonia There is a poor correlation of the blood serum ammonia and hepatic function

2 categories of serum enzymes: Enzymes whose elevation in serum reflects damage to hepatocytes Enzymes whose elevation in serum reflect cholestasis Enzymes that do not fit precisely into either patterns

ENZYMES THAT REFLECT DAMAGE TO HEPATOCYTES AMINOTRANSFERASES: sensitive indicator of liver cell injury and most helpful in recognizing acute hepatocellular diseases such as hepatitis These enzymes are normally present in the serum in low concentrations. They are released in the blood in greater amounts when there is damage to the liver cell membrane resulting in increased permeability

AST (Aspartate aminotransferase): liver, cardiac, skeletal, kidneys, brain, pancreas, lungs, leukocytes and erythrocytes ALT (Alanine aminotransferase): found primarily in the liver

ENZYMES THAT REFLECT CHOLESTASIS Alkaline phosphatase and 5’ nuleotidase: found near the bile canalicular membrane of hepatocytes Gamma Glutamyl Transpeptidase: Endoplamic reticulum and in bile duct epithelial cells  lacks specificity

Alkaline phosphatase: liver, bone, placenta, less commonly small intestine Elevation of liver-derived alkaline phosphatase is not totally specific for cholestasis and a less than 3 fold elevation can be seen in any type of liver disease

TESTS THAT MEASURE BIOSYNTHETIC FUNCTION OF THE LIVER SERUM ALBUMIN: synthesized exclusively by hepatocytes * has a slow turn over not a good indicator of acute or mild hepatic dysfunction

SERUM GLOBULINS: group of proteins made up of gamma globulins (immunoglobulins) produced by B lymphocytes and alpha and beta globulins produced primarily in hepatocytes Increases in the IgM levels are common in primary biliary cirrhosis Increases in the IgA levels occur in alcoholic liver diseases

COAGULATION FACTORS: With the exception of Factor VIII, the blood clotting factors are made exclusively in hepatocytes. Because of their rapid turnover, measurement of the clotting factors is the single best acute measure of hepatic synthetic function and helpful in both the diagnosis and assessing the prognosis of acute parenchymal liver disease

Serum prothrombin time: collectively measures factors II, V, VII, and X Marked prolongation of prothrombin time, >5s above control is a poor prognostic sign in acute in acute viral hepatitis and other acute and chronic liver diseases.

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