Liver Lab Tests Flashcards
What are the 4 major functions of the liver?
- Synthetic function
- Detoxifying function
- Glycemic regulation / metabolic regulation
- glycogen stores
- glucagon
- Largest solid organ in the body
- temperature regulation
Describe the general concept of Enterohepatic circulation
- 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)
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What are th 6 major components of liver function tests?
-
total protein
- albumin = plasma protein
- Aspartate aminotransferase (AST, serum glutamic-oxaloacetic transaminase or SGOT)
- Alanine aminotransferase (ALT, serum glutamic-pyruvic transaminase or SGPT)
- Alkaline phosphatase (ALP)
- Gamma-glutamyl transpeptidase (GGT)
- Bilirubin (conjugated and uncongugated (toral/direct)
What are the 5 “other” liver function tests
- Prothrombin time (PT/INR)
- Ammonia
- insulin/glucose
- platelets
- other exotic tests for fibrosis
What produces alkaline phosphatase?
- Produced by
- bile ducts
- cannaliculi
- gallbladder
- common bile duct
- occasionally- pancreas
- placenta
- osteoblasts
- can get isozymes to identify the source
What to do when you have a patient with elevated alkaline phosphatase?
- 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
Where is AST/ALT produced? How should they be considered?
- 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
Where is AST found?
What reaction does it catalyze?
In addion to livere disease, it is elevated during what medical problem?
- 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
Where is ALT found?
What reaction does it catalyze?
In addion to livere disease, it is elevated under what conditions?
- 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)
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
- 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
How and how much bilirubin is produced a day?
- 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
- 80-85% from red cell senescence - to recycle
- implies total bilirubin (=direct + indirect)
What is the other name for direct bilirubin?
It is elevated in what conditions?
- 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
What is the other name for indirect bilirubin?
It is elevated under what conditions?
- 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
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What do you do if a patient presents with jaundice?
- Liver function panel
- bilirubin direct or indirect– other enzymes?
- heptocellular or cholestatic problem?
- bilirubin direct or indirect– other enzymes?
What is included within total protein?
What artifactually elevates albumin?
What caueses low albumin levels?
- 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
What is the shoter-term synthetic marker for liver function?
When is it elevated?
- Prothrombin time (PT)
- elevated in multiple bleeding disorders
- vitamin K deficiency
- multiple anticoagulants
- cirrhosis
- elevated in multiple bleeding disorders
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General patterns of liver disease?
- 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
Severity of chronic liver disease is described based on whic 2 scores?
- 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
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