Lab 4 Liver Investigations Flashcards
What are liver function tests (LFTs)?
A group of tests that reflect liver status
LFTs are used to differentiate between various liver conditions such as acute hepatocellular damage, cholestasis, and chronic liver disease.
What does ALP stand for and what is its use?
Alkaline phosphatase; used to diagnose cholestasis
ALP is an enzyme that hydrolyzes phosphate esters and is elevated in cholestasis.
What does ALT stand for and what is its significance?
Alanine aminotransferase; used to diagnose hepatocellular damage
ALT is a sensitive indicator of liver damage but not specific, as it can also be found in other tissues.
What does AST stand for and what does it indicate?
Aspartate aminotransferase; used to diagnose hepatocellular damage
AST is another aminotransferase that indicates liver damage but is not liver-specific.
What is the role of GGT?
Gamma-glutamyl transferase; used to diagnose cholestasis
GGT is elevated in conditions affecting bile flow.
What does bilirubin measure in liver function tests?
Capacity of liver to detoxicate and excrete; also used to diagnose jaundice
Elevated bilirubin levels indicate impaired liver function.
What is the purpose of measuring albumin in LFTs?
To measure synthetic capacity of the liver
Albumin levels can indicate liver function and overall health.
What are aminotransferases and why are they important?
Enzymes like ALT and AST that produce non-essential amino acids; sensitive indicators of hepatocellular damage
Increased plasma activity can occur even with minor liver damage.
True or False: ALT and AST are specific to liver damage.
False
ALT and AST can also be found in muscle, heart, and kidney.
What does cholestasis refer to?
Obstruction of bile flow from the liver
Cholestasis can lead to elevated levels of ALP and GGT.
What factors affect the reference ranges for alkaline phosphatase (ALP)?
Age and developmental stage; elevated in children and adolescents, decreased in elderly
These variations are due to factors like bone growth and resorption.
Fill in the blank: ALT and AST are commonly measured _______.
aminotransferases
They are key indicators in liver function tests.
What is Albumin a marker of?
Long term liver function
Albumin has a half-life of 20 days.
What does Prothrombin time measure?
The rate of conversion of prothrombin to thrombin in the presence of coagulation factors
Clotting factors and vitamin K are synthesized by the liver.
What does prolonged Prothrombin time indicate?
Liver dysfunction
Prothrombin time has a half-life of 6 hours.
What is Jaundice?
Yellow discoloration of the skin and the sclera of the eyes due to hyperbilirubinemia
Not detectable until plasma bilirubin >50μmol/L.
What causes pre-hepatic jaundice?
Increased bilirubin production (unconjugated)
Possible causes include haemolysis or decreased albumin levels.
What causes hepatic jaundice?
Decreased bilirubin conjugation (unconjugated)
Possible causes include failure of bilirubin conjugation (Gilbert’s syndrome), hepatitis, malignancy, cirrhosis, or drug interaction.
What causes post-hepatic jaundice?
Decreased bilirubin excretion (conjugated)
Possible causes include gallstones, malignancy, or pancreatitis.
What confirms hyperbilirubinemia?
Total bilirubin
Bilirubin fractions help determine the cause of jaundice.
What do the bilirubin fractions indicate?
Unconjugated → pre-hepatic or hepatic; conjugated → hepatic or post-hepatic
This helps in diagnosing the type of jaundice.
What does AST/ALT suggest?
Hepatocellular damage
These are enzymes that indicate liver cell injury.
What do ALP/GGT indicate?
Cholestasis (hepatic or post-hepatic)
These enzymes are used to assess bile duct obstruction or liver disease.
What does low Albumin suggest?
Compromised synthesis (chronic damage)
Albumin levels can indicate the liver’s ability to produce proteins.
What does prolonged PT suggest?
Compromised synthesis (acute damage)
Prothrombin time reflects the liver’s ability to produce clotting factors.
What is Kernicterus?
Neonatal unconjugated hyperbilirubinemia brain damage
Kernicterus occurs due to high levels of unconjugated bilirubin in neonates.
What causes Kernicterus?
- Immature liver function
- Bilirubin crosses the blood-brain barrier, making it neurotoxic
These factors lead to the accumulation of bilirubin in the brain, resulting in damage.
What bilirubin level indicates the need for phototherapy?
> 200μmol/L
Phototherapy helps convert bilirubin into a water-soluble form for easier excretion.
What is the effect of blue light on bilirubin?
Converts bilirubin to a water-soluble form
This conversion is crucial for reducing bilirubin levels in the body.
What bilirubin level may require exchange transfusion?
> 300μmol/L
Exchange transfusion is a procedure to rapidly reduce high bilirubin levels.
What is cholestasis?
A condition where bile cannot flow from the liver to the duodenum
Cholestasis can lead to various symptoms and complications related to bile flow.
What are the two types of cholestasis?
- Hepatocyte damage (intra-hepatic)
- Obstruction of bile ducts (extra-hepatic)
The type depends on whether the issue is within the liver or in the bile ducts.
List some symptoms of cholestasis.
- Fatigue
- Pruritus
- Dark urine
- Malabsorption of fat-soluble vitamins
- Osteoporosis
- Jaundice
These symptoms arise from bile accumulation and its effects on the body.
What causes pruritus in cholestasis?
Bile salts in the blood irritating PNS nerves
This irritation leads to itching of the skin, a common symptom of cholestasis.
How does cholestasis affect fat-soluble vitamins?
Causes malabsorption
This can lead to deficiencies in vitamins A, D, E, and K.
What is a late-stage symptom of cholestasis?
Jaundice
Jaundice occurs due to the buildup of bilirubin in the body.
What can malabsorption of vitamin D lead to in cholestasis?
Osteoporosis
Vitamin D is essential for calcium absorption and bone health.
What are gallstones?
Deposition of cholesterol or bilirubin in the gallbladder
Gallstones are formed when there is an imbalance in the substances that make up bile.
What is a common cause of post-hepatic cholestasis?
Gallstones
Post-hepatic cholestasis occurs when bile flow is obstructed after it has left the liver.
Which type of gallstones is more common?
Cholesterol stones
Cholesterol stones account for the majority of gallstone cases.
What percentage of adults have gallstones?
1 in 10 adults
This equates to approximately 10% of the adult population.
What proportion of individuals with gallstones develop symptoms?
Minority develop symptoms
Most people with gallstones remain asymptomatic.
About what fraction of individuals with gallstones will develop epigastric pain?
About 1/3
Epigastric pain is a common symptom associated with gallstones.
What are two treatment options for gallstones?
- Endoscopic removal of stones
- Cholecystectomy (remove gallbladder)
Cholecystectomy is often performed when gallstones cause significant problems.
What is a consequence of cholecystectomy?
Cannot concentrate bile
This can lead to difficulties in fat absorption.
What are potential effects of cholecystectomy on digestion?
- Affects fat absorption
- Diarrhoea
Without the gallbladder, bile is released continuously, affecting fat digestion.
What is acute hepatitis?
Acute inflammation of the liver
It can be caused by various factors including infections and metabolic disorders.
List some causes of acute hepatitis.
- EBV
- CMV
- Wilson’s disease
- AAT deficiency
- Viral hepatitis (A, B, C, D, E)
These causes can lead to liver inflammation and damage.
What is true about viral hepatitis?
Usually self-limiting (~80% undiagnosed)
Many cases of viral hepatitis resolve without specific treatment.
What are common symptoms of acute hepatitis?
Flu-like symptoms
Symptoms may include fatigue, fever, and malaise.
What defines acute liver failure?
Severe liver dysfunction with encephalopathy and coagulopathy
It represents a critical condition requiring immediate medical attention.
When can acute liver disease progress to acute liver failure?
When the rate of hepatocyte death exceeds the regenerative capacity of the liver
This progression can occur due to various acute insults to the liver.
What is the diagnostic criterion for acute liver failure regarding INR?
INR > 1.5
This indicates significant liver dysfunction affecting coagulation.
What neurological condition is associated with acute liver failure?
Neurologic dysfunction with any degree of hepatic encephalopathy
This can manifest as confusion, altered consciousness, or coma.
What is a requirement for diagnosing acute liver failure regarding prior liver disease?
No prior evidence of liver disease
This helps differentiate acute liver failure from chronic liver conditions.
What is the disease course duration for acute liver failure?
< 26 weeks
This timeframe is critical for the classification of the condition.
What is cirrhosis?
Cirrhosis is a condition where normal liver tissue is replaced by fibrous (scar) tissue
This condition results from prolonged damage to the liver.
What happens to the liver’s regeneration power in cirrhosis?
The regeneration power is lost due to prolonged damage to the liver
This occurs when hepatocellular damage exceeds hepatocellular regeneration.
What is the relationship between hepatocellular damage and regeneration in cirrhosis?
Hepatocellular damage is greater than hepatocellular regeneration
This imbalance contributes to the progression of cirrhosis.
What is a hallmark of cirrhosis?
Portal hypertension
This condition is characterized by increased blood pressure in the portal venous system.
What does bridging of fibrous tissue between portal triads indicate?
It indicates blood flow obstruction
This is a significant feature of cirrhosis.
What is the typical finding of total bilirubin in chronic liver disease?
Total bilirubin is elevated
This elevation is a common laboratory finding in liver disease.
Which bilirubin fraction is usually higher in chronic liver disease?
Unconjugated bilirubin is greater than conjugated bilirubin
This pattern can help differentiate types of liver dysfunction.
What is the typical AST/ALT pattern in chronic liver disease?
Marked elevation in both AST and ALT
These enzymes are indicators of hepatocellular injury.
What is observed in alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) levels in cholestatic conditions?
Elevation in ALP and GGT
This indicates cholestasis, a condition where bile cannot flow from the liver to the duodenum.
What is the typical albumin level in chronic liver disease?
Albumin is low
This is due to decreased synthesis in the liver.
What is the prothrombin time (PT) status in chronic liver disease?
PT is prolonged
This occurs due to impaired synthesis of clotting factors in the liver.
What are the applications of liver function tests (LFTs)?
Applications include:
* Screening for liver disease
* Diagnosing liver disease
* Prognosis of liver disease
* Monitoring progression of liver disease
LFTs serve multiple purposes in assessing liver health and disease progression.
What must occur before liver function is considered abnormal?
Liver damage must be severe before liver function is abnormal
This highlights the resilience of liver function and the need for significant damage to detect abnormalities.
What are functional assays in the context of liver function tests?
Functional assays include:
* Clearance of metabolic products
* Synthesis of proteins
These assays help assess liver function indirectly.
Why is the term ‘liver function tests’ considered a misnomer?
Very few tests actually measure liver function and it is time-consuming, dependent on hepatic blood flow, and has huge variability
This indicates that LFTs may not provide a complete picture of liver health.
