Medical Liver Disease Flashcards
How is unconjugated bilirubin produced? Where?
Bilirubin is produced by RBC breakdown in the spleen (unconjugated)
Where and how is bilirubin conjugated? What is the purpose of this?
Bilirubin is conjugated in the liver with glucuronic acid to make it soluble and excreted (this is also how drugs are metabolised)
Once that bilirubin reaches the gut, what happens to it?
- Bacteria unconjugate the majority of it so it cannot be absorbed
- BUT some bilirubin is re-absorbed from the gut (along with some bile acids)
What is eneterohepatic circulation?
Enterohepatic circulation refers to the circulation of biliary acids, bilirubin, drugs or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte and transport back to the liver.
What is the commonest sign of liver disease?
Jaundice
At what levels of bilirubin does jaundice become visible?
>40umol/l
Where is jaundice first visible?
First visible in sclera (white of eye)
How is jaundice classified?
Classified according to where the abnormality is in the metabolism of bilirubin;
- Pre-hepatic
- Hepatic
- Post-hepatic
What occurs during pre-hepatic jaundice? What is the most common cause of this?
In pre-hepatic jaundice, there is excess production of bilirubin that overtakes the ability of liver to conjugate the bilirubin and excrete into the gut. –> haemolytic anaemia is most common cause (RBCs broken down excessively)
What is Gilbert’s syndrome? What type of jaundice does it cause?
Gilbert’s syndrome is a mild liver disorder in which the liver does not properly process bilirubin (harmless). Occasionally a slight yellowish color of the skin or whites of the eyes may occur. Other possible symptoms include feeling tired, weakness, and abdominal pain.
Pre-hepatic jaundice (too much bilirubin for liver to deal with)
What occurs during hepatic jaundice?
There is dysfunction of the hepatic cells; liver loses the ability to conjugate bilirubin (often too few functioning cells).
This leads to both unconjugated and conjugated bilirubin in the blood, termed a ‘mixed picture’.
What are the 3 major causes of a loss of functioning liver cells causing hepatic jaundice?
- Acute diffuse liver cell injury
- End stage chronic liver disease
- Inborn errors of metabolism
What causes post-hepatic jaundice?
Bile duct obstruction by a stone, stricture, tumour, narrowing (e.g. bile duct, pancreas).
Describe the bilirubin in pre-hepatic jaundice. What are the symptoms?
- This bilirubin is unconjugated (has not reached liver yet) so is insoluble and instead is bound to albumin
- It cannot be excreted by kidneys/liver so causes yellow eyes/skin only
Describe the bilirubin in hepatic jaundice. What are the symptoms?
- Bilirubin is mainly conjugated so is water soluble
- Symptoms; yellow eyes/skin and dark urine
Describe the bilirubin in post-hepatic jaundice. What are the symptoms?
- Bilirubin is conjugated so is soluble and can be excreted
- BUT bilirubin cannot get out of the bile duct into the gut
- Symptoms; yellow eyes/skin, dark urine and pale stools (as bilirubin that would normally give colour to stools is no longer there)
In which type of jaundice would you see dark urine?
Hepatic AND post-hepatic
In which type of jaundice would you see pale stools?
In post-hepatic jaundice
In which type of jaundice would you see yellow eyes/skin only?
Pre-hepatic jaundice
What are the 4 main components of liver function tests (LFTs)?
- Bilirubin (conjugated and unconjugated)
- Liver enzymes (this is a ‘damage’ test rather than a ‘function’ test)
- Albumin
- Clotting factors
What can the bilirubin result from the LFT indicate?
Gives idea if pre-hepatic, hepatic or post-hepatic cause depending on if bilirubin is conjugated or unconjugated
What does a rise in liver enzymes indicate?
Liver damage/disease –> released by dead/dying liver cells
What are the 2 main types of liver enzymes tested for in LFTs?
- Those that leak from hepatocytes; ALT, AST aminotransferases
- Those that leak from bile ducts; Alk phos
Which liver enzymes leak from hepatocytes?
ALT, AST aminotransferases
Which liver enzymes leak from bile ducts?
Alk phos
What can the relative increase of Alanine aminotransferase (ALT) and/or Aspartate aminotransferase (AST) vs Alkaline phosphatase indicate?
Indicates whether injury is mainly to hepatocytes, bile duct cells or both
What would a mild increase in ALT/AST aminotransferases indicate?
Chronic liver disease
What would very high levels of ALT/AST aminotransferases indicate?
Severe acute liver disease
What would raised Alk phos levels indicate?
Obstructive jaundice and chronic biliary disease
Describe albumin levels in chronic liver disease
Low
What are clotting factors and albumin synthesised by? How does liver function affect their levels?
Clotting factors and albumin are proteins manufactured by hepatocytes - levels fall when insufficient liver synthetic function
What can cause low albumin levels?
- Chronic liver insufficiency
- Insufficient intake due to poor diet or malabsorption
- Increased urinary excretion due to leaky glomeruli = nephrotic syndrome
Describe half life of albumin?
Long
How are levels of clotting factors affected by liver disease? Why?
- Short half life –> low levels in acute liver disease and liver failure
- The factors have a short half life so PT is prolonged after just a few days of severe liver injury
Why is poor clotting also seen in patients with obstructive jaundice?
Malabsorption of vitamin K results in hypoprothrombinaemia and a fall in the concentration of the other vitamin K-dependent pro- and anticoagulation factors.
I.e. lack of bile –> vitamin K not absorbed –> lack of clotting factors
After the initial LFTs, what 2 other investigations can be done?
- Ultrasound scan to check for dilated ducts in obstruction
- Only if no dilated ducts do a liver biopsy to find out the cause of jaundice
What are most non-obstructive jaundice cases caused by?
Acute hepatitis
What is the first histopathological feature in a liver with obstructive jaundice?
Bile in the liver parenchyma (liver looks green)
Which other histological features become apparant over time in obstructive jaundice?
- Portal tract expansion
- Oedema
- Ductular reaction – proliferation of ductules around the edge of portal tracts
- Bile salts and copper can’t get out
- Accumulate in hepatocytes
- Bile salts in skin = itch
What characterises a ductular reaction?
Characterised by the proliferation of reactive bile ducts induced by liver injuries (pathologically recognised as bile duct hyperplasia).
What causes an ‘itch’ in obstructive jaundice?
Bile salts accumulating in skin
What is hepatitis?
Inflammation of the liver causing raised liver enzymes (of any cause)
What defines acute vs chronic hepatitis?
- Acute hepatitis –> Acute liver injury caused by something that goes away
- Chronic hepatitis –> Chronic liver disease caused by something that doesn’t go away and features result from balance of damage and attempts at repair
Clinical presentation of acute hepatitis?
Wide clinical sepctrum; asymptomatic, malaise, jaundice, coagulopathy, encephalopathy, death
What does that lasting effect of acute hepatitis depend on?
Depends on how many hepatocytes are damaged at once, and how good the liver is at regenerating – can lose up to 40/50% of liver cells in healthy adult liver and it can regenerate back to it’s normal mass within weeks
What are the 4 major causes of acute hepatitis?
- Viral hepatitis
- Drug induced hepatitis
- Autoimmune hepatitis
- Unknown cause (seronegative)
What is an acidophil body?
An acidophilic (eosinophilic / pink-staining on H&E) globule of cells that represents a dying hepatocyte often surrounded by normal parenchyma.
What are the 5 major categories of causes of chronic hepatitis?
- Immunological injury - virus, autoimmune, drugs
- Toxic/metabolic injury - fatty liver disease (alcoholic or non-alcoholic), drugs
- Genetic inborn errors - iron, copper, alpha 1 antitrypsin
- Biliary disease - autoimmune, duct obstruction, drugs
- Vascular disease - clotting disorders, drugs
Clinically ‘chronic hepatitis’ is a persistence of abnormal liver tests for how long?
More than 6 months
What is the most common category of causes of chronic hepatitis?
Toxic/metabolic injurys - fatty liver disease, drugs
Which test is often used to identify which of these 5 categories is the cause of chronic hepatitis?
Liver biopsy
Describe the progression of fibrosis in chronic liver disease
- Remodelling results in bands of fibrosis that bridge between portal tracts and hepatic veins (portal –> bridging fibrosis)
- Gradually remodelling becomes complete, and hepatocytes form nodules surrounded by fibrous tissue
- Portal blood entering the liver can flow through vessels in the fibrous tissue, and not percolate through sinusoids
- The cirrhotic liver therefore is inefficient in its metabolic function, even though it is or normal size or larger
Despite the cirrhotic liver being normal or even of a larger size, why is it ineffective in its metabolic function?
Portal blood entering the liver can flow through vessels in the fibrous tissue, and not percolate through sinusoids.
Which forms of hepatitis are bloodborne?
B and C
What are the hepatotrophic viruses?
- A, B, C, E
- D = only in people with Hep B
Which other viruses can cause hepatitis as part of systemic disease?
EBV, CMV, HSV (usually immunocompromised host)
How is hepatitis E transmitted?
- Is a waterborne virus
- Spread through contact with the faeces or vomit of an infected person
- Also linked to undercooked pork and pork products (zoonosis)