Liver Function Tests Flashcards
Functions of the Liver:
- Production of plasma proteins
- Glucose homeostasis (production occurs significantly at night)
- Lipoprotein synthesis (sex hormones)
- Bile Acid Production- LDL production
- Vitamin B12, A, D, E, K storage
What are some additional functions of the Liver?
Detoxification of medications and endogenous substances (50% of drugs metabolized in the liver)
- primarily through CYP450 enzyme
- purpose to take fat soluble medication and convert to water soluble for purposes of renal excretion
Production of clotting factors
True/False LFTs are not great indicators of liver functioning?
True, they are better markers of liver injury and abnormalities in bile flow. If your liver is not working it is not going to produce enzymes.
Normal liver enzymes can be present in the setting of liver damage (seen with Hep C, 33% of these patients have normal liver function tests)
What are some guidelines for Hep C screening?
1945-1965 should be screened, patients < 60 should be given Hep B, with diabetes they have a 2-4 fold greater risk of Hep B infections, also giving Hep A.
What are the best indicators of liver function? Labs?
Albumin, Bilirubin, and prothrombin test
AST/ALT will provide more information on liver injury
What serves as an index of liver functioning/synthesis ability?
Albumin
Albumin is synthesized specifically by the?
Liver
________ is essential for the transportation of endogenous and exogenous substances and drugs?
Albumin
What is the half life of albumin?
3 weeks
With what conditions do we see low albumin?
Malignancy, chronic liver disease
Up to 80% of patients with cirrhosis have normal albumin
When would we see low albumin with normal LFTs?
- Non hepatic causes such as protein loss (proteinuria), acute or chronic inflammatory states, burns, sepsis, trauma, rhuematic disorders, and IV fluids
______results from enzymatic breakdown of heme in the body?
Bilirubin
Unconjugated (indirect) and conjugated (direct BADghh)=?
Total bilirubin
If total bili is elevated ask for a breakdown
______levels do not become elevated until the liver has lost at least 1/2 of its excretory capacity.
Conjugated
- rarely present in the blood in healthy individuals
- when it is elevated there is a marked decrease in the secretion of bile (marked elevation in bilirubin in serum and urine).
- Hepatobiliary disease is very common
True/False Is it common to see an elevation in Bilirubin after fasting (12-24 hours)
True
With what conditions do we typically see elevated unconjugated (indirect) bili with normal CBC?
Gilberts Syndrome
Neonatal jaundice
With what conditions do we see elevated conjugated (direct) bili?
Hepatobiliary disease
Cholestasis/hepatocelluar disease of all types
Causes of increased ALT or AST in asympotmatic patients:
A- autoimmune hepatitis B- Hep B C- Hep C D- Drugs or toxins (too much iron can cause this) E- Ethanol F- Fatty Liver (Very common cause of elevated liver enzymes) G- Growths H- Hemodynamic disorders (CHF) I- Iron (Copper) M- Muscle Injury
3/4 of all elevated AST/ALT values are caused by:
- ETOH
- Hep B
- Hep C
- Fatty Liver (NASH)- 2nd most common reason to need liver transplant
This enzyme is found within the liver cell, it rises rapidy with hepatic injury, resolves very quickly (half life of 17 hours)
AST
True/False AST is not as specific to liver as ALT
True, AST is NOT as specific to liver as ALT
What should your differentials be if AST is elevated more than ALT?
Alcohol, Statin, Tylenol
____ is more specific to liver than AST
ALT
Half life of 47 hours
When ALT is more elevated that AST treatment includes:
Avanndia or actos
LIver infection or diseases- fatty liver
Toxic agents
What is the approach for asymptomatic elevation?
- For an individual who is asymptomatic and picked up on screening or monitoring for various medications
- Repeat enzymes in next 2 weeks
- Avoid ETOH, Acetaminophen, Ibuprofen
- 50% of individuals have normal LFT upon repeat
- VIP to remember HEP C patients may have fluctuating LFTs and you may be falsely assured.
What does the Degree of Elevation provide:
Significant clues as to the etiology of the liver problem.
- < 5 times- mild
- 5-10 times- moderate
- > 10 times
- > 1000 units/L- hepatitis, drugs or toxins, acute biliary obstruction
What is a normal AST range?
0-40
What is a normal ALT range?
0-40
What gives us an AST/ALT ratio?
AST/ALT= ratio
If AST/ALT ratio >1 highly suggestive of what?
Alcoholic LIver DIsease, if >2 HIGHLY suggestive of ETOH liver disease
If AST/ALT >1 consider?
AST
True/False AST/ALT <1 is the most encountered abnormality
True Should consider: Avandia/Actos Liver infection or disease (NASH/Fatty Liver) Toxic agents (Iron)
______is a liver disease thought to be present in 23% of Americans.
Fatty Liver
A patient who presents with obesity, HTN, Diabetes, and Hyperlipidemia most likely has:
Fatty Liver- typical patient
In Fatty Liver the AST/ALT ratio will typically be what?
Initially <1
Can shift >1, indicative of advanced fibrosis
Patients will also have GGT up to 3x Upper Limits of Normal
What are some other differentials of AST/ALT <1?
Hep A Igm
Hep B sAg
ANti Hep C
Hemochromatosis-autosomal recessive condition which can be caused by ETOH
What is hemochromatosis?
Abnormal deposition of iron in the liver, heart and pancreas
What lab results are typically seen with hemochromatosis?
AST/ALT <1
Elevated Ferritin (>300+)
Transferrin Saturation Index >45% is highly suggestive of this condition. Need a eval and biopsy.
Labratory findings of elevated CK-MM of 500-100,000 units/L, BUN/Creatinine ratio <5 (normal 10), and increased serum uric acid is indicative of what condition?
Rhabdomyolysis
CK-MM is the most sensitive test and the degree of elevation correlates with the relative risk of renal failure
Also with this condition, creatine phosphate is released from damaged muscle and is converted into creatinine. And uric acid levels can be markedly elevated > 40mg/dl
