(59a) Diseases of the Hepatobiliary system Flashcards
Name 3 medical liver diseases
- jaundice
- hepatitis
- cirrhosis
What is the commonest sign of liver disease?
Jaundice
When is jaundice visible and where?
When bilirubin is higher than 40umol/l
First visible in the sclera of the eye
What are the 3 types of jaundice?
classified according to where the abnormality is in the metabolism of bilirubin
- pre-hepatic
- hepatic
- post-hepatic
What are the causes of pre-hepatic jaundice?
Too much bilirubin produced
- haemolytic anaemia
What is bilirubin?
The yellow breakdown product of normal heme catabolism, caused by the body’s clearance of aged red blood cells which contain hemoglobin. Bilirubin is excreted in bile and urine, and elevated levels may indicate certain diseases
What are the causes of hepatic jaundice?
Too few functioning liver cells
- acute diffuse liver cell injury
- end stage chronic liver disease
- inborn errors
What are the causes of post-hepatic jaundice?
Bile duct obstruction
- stone or structure
- tumour of the bile duct or pancreas
Describe the pathway of bilirubin metabolism
- bilirubin is produced by red blood cell breakdown (unconjugated)
- metabolised in the liver (conjugated) and excreted in bile
- some bilirubin is re-absorbed from the gut (enterohepatic circulation)
- also bile salts
Where are erythrocytes broken down and unconjugated protein-bound bilirubin produced?
In the spleen
Where does conjugation of bilirubin occur? (becomes water-soluble)
In the liver
Where is urobilinogen produced?
In the intestines
Which protein carries unconjugated bilirubin?
Albumin
Describe the difference in solubility between unconjugated and conjugated bilirubin?
Unconjugated bilirubin = lipid-soluble
Conjugated bilirubin = water-soluble
What happens to conjugated bilirubin after the liver?
It is excreted in bile into the small intestine through the bile duct
What happens to conjugated bilirubin once it is in the small intestine?
Gets to ileum or first part of large intestine and is converted to urobilinogen (urobilinogen = lipid-soluble)
Most urobilinogen is oxidised to what?
Sterocobilin
Sterocobilin is responsible for what?
The brown colour of faeces
Describe the bilirubin in pre-hepatic jaundice
- unconjugated
- bound to albumin
- insoluble
- not excreted
What would the signs be in pre-hepatic jaundice?
Yellow eyes and skin only
Describe the bilirubin in hepatic jaundice
- mainly conjugated
- soluble
What would the signs be in hepatic jaundice?
Yellow eyes and dark urine
Describe the bilirubin in post-hepatic jaundice
- conjugated
- soluble
- excreted
- but can’t get into gut
What would the signs be in post-hepatic jaundice?
Yellow eyes, pale stools and dark urine
The site of abnormality of bilirubin excretion can be deduced from what?
Clinical history of skin, urine and faeces colour
Why are liver enzymes measured in liver function tests?
Damage to cells in the liver causes enzymes to leak from the cells
Which enzymes leak from damaged hepatocytes? (measured in liver damage tests)
- ALT (alanine aminotransferase)
- AST (aspartate aminotransferase)
What leaks damaged bile ducts? (measured in liver damage tests)
Alkaline phosphate
What 3 things are measured in liver function tests?
- bilirubin
- albumin
- clotting factors
What would raised conjugated bilirubin without extrahepatic duct obstruction indicate?
Disease of hepatocytes or intrahepatic ducts
Why are clotting factors and albumin measured in LFTs?
They are manufactured by hepatocytes - so levels fall when insufficient liver synthetic function
When would albumin levels be low?
In chronic liver disease (has a long half life)
could also be due to insufficient dietary intake, or nephrotic syndrome causing increased urinary excretion
When would clotting factors be low?
Acute liver disease and liver failure (short half life)
Why is poor clotting also seen in patients with obstructive jaundice?
Can’t absorb fat-soluble vitamins (vitamin K)
What is the first histopathological feature in the liver of obstructive jaundice?
Bile in the liver parenchyma (jaundice in skin)
What are the further signs of obstructive jaundice with increasing time?
- portal tract expansion
- oedema
- ductular reaction (proliferation of ductules around the edge)
- bile salts and copper cannot get out (accumulate in hepatocytes, bile salts in skin = itchy)
Eventually, severe chronic liver disease and cirrhosis
What is used to first investigate a patient with jaundice?
Ultrasound scan (USS) to check for bile duct dilatation - if ducts are not dilated, then lover biopsy may be performed to investigate cause of jaundice
What is seen on obstructive jaundice, perivenular (zone 3) changes?
Bile pigment is visible in bile plugs which show that bile has been excreted by hepatocytes into intracellular canaliculi but accumulated because of low bile flow
- also get swelling and irregularity of hepatocytes, and increased activity of Kupffer cells phagocytosing dead hepatocytes
Were are the changes to the portal tract in obstructive jaundice?
Gets larger, initially due to swelling (oedema, tissue looks pale) then you get ductular reaction (increased number of small bile ducts around periphery of tracts) and some associated inflammatory cells including neutrophils
Over time, oedema reduces and fibrosis increases - characteristic appearance = biliary gestalt
Most non-obstructive cause of jaundice are due to what?
Acute hepatitis
What is acute hepatitis?
Inflammation in the liver, can only really be seen with liver biopsy (no classical pain and swelling etc) - symptoms usually mild/non-existant unless severe - recent onset and will resolve back to normal if cause does not persist
What is chronic hepatitis?
Present for over 6 months, results in ongoing liver cell injury and progressive structural liver damage of scarring and remodelling
The severity of acute hepatitis depends on what?
How many hepatocytes are damaged at once, and how good the liver regeneration is
What is at the most severe end of the spectrum in acute hepatitis?
- coagulopathy
- encephalopathy (confusion, coma)
- death
What are the causes of acute hepatitis?
- inflammatory injury (viral, drugs, autoimmune, unknown = seronegative)
- toxic/metabolic injury (alcohol, drugs eg. paracetamol)
Which viruses can causes severe inflammatory injury (acute hepatitis)?
Hepatitis A, B, E
What is DILI?
Drug-induced liver injury
How is the overall appearance of acute hepatitis on biopsy described?
Lobular disarray
What is seen on biopsy in acute hepatitis?
- apoptotic hepatocytes (acidophil body) = spotty necrosis
- inflammatory cells
- hepatocytes vary in size
Overall = lobular disarray
What is seen on biopsy in the more severe end of the spectrum of acute hepatitis?
Whole confluent areas of necrosis of hepatocytes = confluent panacinar necrosis
What is acute hepatitis with bridging necrosis?
Intermediate-severity acute hepatitis
Confluent necrosis of adjacent hepatocytes in a ‘bridge’ between a portal tract and hepatic vein
What are the 5 groups of causes of chronic hepatitis?
- immunological injury
- toxic/metabolic injury (fatty liver disease)
- genetic inborn errors
- biliary disease
- vascular disease
What is the most common group of causes of chronic hepatitis?
Toxic/metabolic injury
What can identify which of the 5 groups is the causes of chronic liver injury?
Liver biopsy
What are the immunological causes of chronic liver injury?
- virus
- autoimmune
- drugs
What are the toxic/metabolic causes of chronic hepatitis (fatty liver disease)?
- alcohol
- non-acoholic fatty liver disease (NAFLD)
- drugs