Normal & Abnormal Liver Function Tests Flashcards

1
Q

Biochemical Tests of Liver Disease

A
  • no easy measure of hepatic clearance or function
  • no highly sensitive or specific test for underlying liver disease
  • liver is a silent organ associated with often nonspecific symptoms (fatigue)
  • all biochemical tests have limitations in prediction function and prognosis
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2
Q

Complications of Liver Disease

A
  • synthetic impairment
  • cholestasis-impairment of bile flow
  • decreased clearance
  • portal hypertension - portal blood is shunted around the liver and not processed by the liver
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3
Q

Biochemical Tests of Liver Disease

“Liver Function Tests”

A
  • often biochemical measures of hepatocellular injury or impairment of bile flow
  • true “function” tests are measures of clearance or synthetic function
  • few clinically useful hepatic clearance tests - measuring drug clearance (like Lidocaine)
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4
Q

Liver Chemistries

A

Tests which detect injury: aminotransferases & Alkaline phosphatase
Tests which measure clearance: bilirubin, ammonia
Tests of Synthetic Capacity: clotting factors made by liver, albumin, cholesterol - late complication of severe dysfunction

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5
Q

Aminotransferases

A
  • aspertate aminotransferase (AST)
  • alanine aminotransferase (ALT)
  • increase associated with cell injury or death
  • AST elevation also increased with muscle injury
  • ALT more specific for liver injury
  • Marked elevations associated with primary hepatocellulary injury
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6
Q

Alkaline Phosphatase

A
  • Enzyme derived from bile ducts
  • Correlates with intrahepatic & extrahepatic injury or obstruction
  • Level associated with increased synthesis
  • 3 important isoenzymes: Gut, Liver, Bone
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7
Q

Cholylglycine

A
  • serum bile salt

- correlates with the degree of cholestasis, intrahepatic or extrahepatic obstruction to bile flow

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8
Q

Gamma Glutamyl Transferase (GGT)

Gamma Glutamyl Transpepidase

A
  • enzyme in many tissues including biliary ductules
  • increased with cholestasis, biliary obstruction
  • increased w/induction by numerous chemicals (Phenytoid/Dilantin & ethanol)
  • many meds & chemicals induce GGT that is limited to clinical utility
  • isolated GGT elevation is often due to medications or ethanol
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9
Q

Blirubin

A
  • level represents a balance b/w input & hepatic removal
  • imperfect measure of hepatic clearance & excretory function
  • inc. w/impaired clearance by the liver
  • inc. w/intrahepatic & extrahepatic obstruction
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10
Q

Ammonia

A
  • detoxified in liver by Urea cycle & glutamine synthetase reaction
  • in chronic liver disease function & protosystemic shunts around liver
  • often, but not perfect correlation w/hepatic encephalopathy
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11
Q

Synthetic Function Tests

A
  1. Prothrombin Time: prolonged when factors I, II, V, VII, X deficient or Vit. K deficient, correlates well with hepatic synthetic function
  2. International Standardize Ration (INR)
  3. Albumin: T1/2 ~20 days, hepatic synthesis, rapidly changed with acute illness, malnutrition
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12
Q

Child Pugh Score

A
A is best
B in between
C is most impaired 
based on: alb, bili, ascites, enceph, PT/INR
Transplant 9-10
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13
Q

Model of End-Stage Liver Disease (MELD)

A

international normalized ration (INR) - standardized measure of Prothrombin time, hepatic synthetic function

  • bilirubin
  • creatinine
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