Liver Lab Tests

Question 1

What are the 4 major functions of the liver?

Answer 1

• Synthetic function
• Detoxifying function
• Glycemic regulation / metabolic regulation
  
  • glycogen stores
  • glucagon
• Largest solid organ in the body
  
  • temperature regulation

Question 2

Describe the general concept of Enterohepatic circulation

Answer 2

• As break down aromatic rings
  
  • end up encorporated into various stuff & excreted into bile
  • want to recover it b/c requires substantial energy
  • reabsorb selectively throught the intestine, goes to the liver via the portla vein, and exits via bile acid (reabsorbed)

Question 3

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Question 4

What are th 6 major components of liver function tests?

Answer 4

1. total protein
   
   1. albumin = plasma protein
2. Aspartate aminotransferase (AST, serum glutamic-oxaloacetic transaminase or SGOT)
3. Alanine aminotransferase (ALT, serum glutamic-pyruvic transaminase or SGPT)
4. Alkaline phosphatase (ALP)
5. Gamma-glutamyl transpeptidase (GGT)
6. Bilirubin (conjugated and uncongugated (toral/direct)

Question 5

What are the 5 “other” liver function tests

Answer 5

• Prothrombin time (PT/INR)
• Ammonia
• insulin/glucose
• platelets
• other exotic tests for fibrosis

Question 6

What produces alkaline phosphatase?

Answer 6

• Produced by
  
  • bile ducts
  • cannaliculi
  • gallbladder
  • common bile duct
  • occasionally- pancreas
  • placenta
  • osteoblasts
• can get isozymes to identify the source

Question 7

What to do when you have a patient with elevated alkaline phosphatase?

Answer 7

• Any good reason to have an elevated alkaline phos?
  
  • pregnant?
  • burn turnover? (fracture/cancer)
  • degree severity of bile tree?
    
    • causing bilirubin to go up?
  • from liver? – GGT
    
    • if hepatic cause, GGT will also be elevated
    • <3x elevatin
      
      • consider hepatocelluar injury
      • viral/alcoholic hepatitis
      • drug-induced
    • >3x elevation
      
      • hepatobilliary
      • ductal obstruction? - imaging/ultrasound
        
        • if common bile duct is obstructed, you know the problem is distal
        • if just hepatic ducts are dialated, obstruction is more proximal

Question 8

Where is AST/ALT produced? How should they be considered?

Answer 8

• Produced WITHIN the hepatocytes
  
  • motsly..
  • shouldn’t be found outside the hepatocytes or indicates hepatocellular damage
  • ration may yielf more info
  • evaluate TOGETHER to find a pattern

Question 9

Where is AST found?

What reaction does it catalyze?

In addion to livere disease, it is elevated during what medical problem?

Answer 9

• Found
  
  • heart, liver, muscle, kidney, brain, pancreas, slpeen and lung
  • catalyzed w/ Vit B6 converstion between alpha-ketoglutarate + aspartate glutamate + oxaloacetate
  • more sensitive but less specific in detecting liver disease
  • elevated in 98% of patients with acute MI

Question 10

Where is ALT found?

What reaction does it catalyze?

In addion to livere disease, it is elevated under what conditions?

Answer 10

• found in liver and kidney
• caralyzes teh interconversion (with Vit B6) of alpha-ketoglutarate + alanine glutamate + pyruvate
• elevates in 60% of patients on heparain (returns to normal when stopped)

Question 11

What medical conditions are associated with the following AST/ALT rations?

• 2.0 - >6.0
• >2.0
• 1.4 - 2.0
• >1.5
• <1.4
• 1.3
• 0.8
• 0.5 - 0.8

Answer 11

• 2.0 - >6.0 alcoholic liver disease
• >2.0 organic toxic hepatitis
• 1.4 - 2.0 cirrhosis
• >1.5 interhepatic cholestasis
• <1.4 extrahepatic cholestasis
• 1.3 chronic active hepatitis
• 0.8 extra hepatic biliary obstruction
• 0.5 - 0.8 acute viral hepatitis

Question 12

How and how much bilirubin is produced a day?

Answer 12

• Tetrapyrrole pigment
• breakdown product of heme (ferroprotoporphyrin IX)
• 4mg/kg/day produced
  
  • 80-85% from red cell senescence - to recycle
    
    • in spleen/liver
  • remainder from cytchromes, myoglobin, and premature heme/cell destruction
• implies total bilirubin (=direct + indirect)

Question 13

What is the other name for direct bilirubin?

It is elevated in what conditions?

Answer 13

• AKA conjugated bilirubin
• shorter elimination half-life
• elevated in
  
  • biliary tract obstruction
  • Dubin-Johnson Syndrome
    
    • genetics
  • Rotor’s syndrome
    
    • genetics
  • can elevate in any hepatocellular disease

Question 14

What is the other name for indirect bilirubin?

It is elevated under what conditions?

Answer 14

• uconjugatd bilirubin
• albumin-bound in plasma
• can represent hemolysis
  
  • b/c as bilirubin is produced it gets converted to unconjugated first & then to conjugated
• Crigler-Najjar
  
  • genetics
• Gilberts syndrome - physiologic stress
  
  • genetics

Question 15

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Question 16

What do you do if a patient presents with jaundice?

Answer 16

• Liver function panel
  
  • bilirubin direct or indirect– other enzymes?
    
    • heptocellular or cholestatic problem?

Question 17

What is included within total protein?

What artifactually elevates albumin?

What caueses low albumin levels?

Answer 17

• Total protein
  
  • includes (prealbumin, albumin, alpha-1 globulin, alpha-2 globulin, beta globulin, and gamma globulin fractions)
• Albumin
  
  • produced by liver
  • elevated (artifactually) by dehydration
  • low in
    
    • malnutrition
    • liver disease
    • nephrotic syndrome
    • protein-losing enteropathy

Question 18

What is the shoter-term synthetic marker for liver function?

When is it elevated?

Answer 18

• Prothrombin time (PT)
  
  • elevated in multiple bleeding disorders
    
    • vitamin K deficiency
    • multiple anticoagulants
    • cirrhosis

Question 19

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Question 20

General patterns of liver disease?

Answer 20

• Hepatocellular damage
  
  • transaminases will be the most deranged
• Hepatobiliary diseases
  
  • bilirubin / AlkPhos will be the most deranged
• some processes involve BOTH
• kinetics of enzymes is relevant
• don’t forget the non-hepatic causes

Question 21

Severity of chronic liver disease is described based on whic 2 scores?

Answer 21

• MELD score – Model end stage liver disease (12 to get on transplant list)
  
  • incorporates multiple prognostic items
  • devised for ranking transplant lists
• Child-Pugh
  
  • Class a/b/c for dosing medications

Question 22

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Question 24

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