Liver disease Flashcards
How does the liver metabolise drugs?
Phase 1: Either oxidation, reduction or hydrolysis of the drug to add functional chemical groups to make it polar
CYP450 enzymes involved
In smooth endoplasmic reticulum
Phase 2: phase1 products conjugated with endogenous substrates such as glycine, glucuronic acid or sulfuric acid.
Makes them more water soluble and excretable in urine
Phase 3: Excretion (most commonly in kidneys) and can only occur if products are water soluble and small.
If molecule is high polar with a greater molecular weight then its removed via biliary excretion
What drugs can lead to hepatic failure?
Paracetamol (acetaminophen) Antibiotics (ciprofloxacin, erythromycin, isoniazid) Antidepressants (amitriptyline) Anti-epileptics (phenytoin, valproate) Anesthetic agents (halothane) Statins Immunosuppressive (cyclophosphamide and methotrexate) Salicylates (due to Reye syndrome) NSAIDs
Chronic Alcohol use with some of these drugs causes synergy
What is the effect of acute alcohol consumption on drug metabolism?
Acute consumption can have an inhibitory effect of CYP450 so drugs are metabolised slower
Hepatoxicity can occur at lower doses
How can adverse drug reactions be classified?
Type A (Intrinsic/pharmacological): 80% of all hepatotoxicities These drugs have a predictive dose-response curve and a MOA of toxicity Rarely dangerous and normally occurs after single dose
Type B (idiosyncratic) Rare, non-predictable, toxicity not related to dose and has variable latency time periods May be due to reactive metabolites causing a hypersensitivity reaction
How does paracetamol cause hepatotoxicity?
Type A adverse reaction (safe in therapeutic doses)
Drug undergo conjugation with glucuronic acid -> water-soluble product BUT large amounts causes saturation some of the drug gets metabloised by CYP450 enzyme
This can form toxic NAPQI and deplete stores of glutathione so the toxic intermediate can no longer be conjugated into safe metabolite
How can alcohol cause hepatitis?
Converted to acetaldehyde in the liver via alcohol dehydrogenase in hepatocytes producing reactive oxygen radicals (e.g. HO, hydroxyl, superoxide anion)
NAD converted to NADH causing fatty acid production and steatosis
Radicals can destroy hepatocytes. Acetaldehyde binds to macromolecules and cell membrane to form acetaldehyde adducts (recognised as foreign bodies) causing immune response
Neutrophil infiltration and inflammation.
What histological change occurs in the liver due to alcoholic hepatitis?
Mallory bodies form: damaged intermediate filaments within the cytoplasm of hepatocytes. Aggregate together, are highly eosinophilic and appear pink on H&E staining.
Physiology of bilirubin metabolism:
Erythocytes go through haemolysis after 2-3 months in spleen -> Unconjugated bilirubin (Biliverdin)
This is fat -soluble and travels to liver via albumin blood plasma proteins and then conjugates with glucuronic acid in liver
Conjugated bilirubin (water soluble now) does not get absorbed by terminal ileum and goes to colon
Here, the healthy commensal deconjugate it to colourless urobilinogen
50% of urobillinogen is reabsorbed and taken up via portal vein to the liver -> kidneys -> oxidised into urobilin -> yellow colour of pee
OR urobilinogen remains in colon and is reduced to Stercobilinogen -> oxidised to stercobilin -> brown colour of poo
What are the investigations for jaundice?
Urine sample (identify presence of bilirubin),
Haematology FBC (INR, LFTs, prothrombin time and platelet count)
U&Es, total protein albumin
Blood culture and liver serology
Ultrasound (distended ducts, gallstones, pancreatic mass)
ERCP and MRCP
Anti-mitochondrial antibody
Viral markers (HIV, Hep ABC)
What can be the causes for pre-hepatic jaundice?
Increased rate of haemolysis: Malaria Sickle cell Thalassaemia Haemolytic Anaemia
Gilbert’s syndrome (lack of conjugation of bilirubin)
Criggler-Najjar syndrome
No bilirubin present in urine but high levels of unconjugated bilirubin in serum
What is Gilbert’s syndrome?
genetic disorder where there are elevated levels of unconjugated bilirubin in bloodstream due to UGT1A1 enzyme mutation
Reduced activity of glucoronyltransferase enzyme which is needed for conjugation of billirubin
What are the hepatic causes of jaundice?
Liver damage that causes only some of the bilirubin to be conjugated with glucuronic acid
Hepatitis/Hepatotoxicity Liver Cirrhosis Alcoholic liver disease Drugs Hereditary haemochromatosis (hepcidin) Primary sclerosing cholangitis/ primary biliary cirrhosis
Mixture of conjugated and unconjugated bilirubin present. Plasma albumin levels are low.
What are the post-hepatic causes of jaundice?
Obstructive jaundice:
Choledocholithiasis
Head pancreatic cancer
biliary-atresia (failure of formation of tubes)
Cholangiocarcinoma (cancer of gallbladder)
Conjugated bilirubin present in urine but no urobilinogen
Pale stools and dark urine (as no conversion to urobilinogen therefore no stercobilin)
Comment on the levels of following in pre-hepatic jaundice: Total bilirubin Conjugated bilirubin Unconjugated bilirubin Urobilinogen ALP levels ALT and AST levels Conjugated bilirubin in urine Large spleen
TB- Increased CB - Normal UB - Increased U - Normal ALP - Normal ALT/AST - Normal CB in urine: Not present Large spleen
Comment on the levels of following in hepatic jaundice: Total bilirubin Conjugated bilirubin Unconjugated bilirubin Urobilinogen ALP levels ALT and AST levels Conjugated bilirubin in urine Large spleen
TB- Increased CB - Potentially increased UB - Potentially increased U - Decreased ALP - Increased ALT/AST - Increased CB in urine: Present Large spleen
Comment on the levels of following in post-hepatic jaundice: Total bilirubin Conjugated bilirubin Unconjugated bilirubin Urobilinogen ALP levels ALT and AST levels Conjugated bilirubin in urine Large spleen
TB- Increased CB - Increased UB - Normal U - Decreased ALP - Increased ALT/AST - Increased CB in urine: Present Absent Large spleen
What are the main sources of Alkaline Phosphatase?
1- Cells of hepatobiliary tract
2- Osteoblasts of bone
3- Intestine and placenta &renal tubules.
What can be used to ascertain whether increased ALP is due to bone or hepatobiliary disease?
GGT will be normal in bone diseases
What can cause a clinically significant raised level of ALP?
periods of active bone growth in infancy and at puberty
Pregnancy 2nd and 3rd trimesters due to placental ALP
Osteogenic tumours
Paget’s disease of bone
Rickets/osteomalacia
Hyperparathyroidism
Healing of bone fractures
Obstructive jaundice
Cholestasis, cholangitis, gallstones, cholecystitis
Hepatitis
Why does GGT (gamma glutamyl transferase) increase?
Present in blood, originates in hepatobiliary system
Causes of increase:
1- Alcohol, drug (anticonvulsants) cause increased secretion of GGT
2- Biliary obstruction (esp obstructive jaundice)
Increases earlier than ALP and persists longer
3- Hepatitis
4- Liver tumours
Causes of increased blood amninotransferases (ALT/AST)
1- Hepatitis (in viral ALT is more elevated than AST)
2- Cirrhosis (AST is more elevated in chronic disease)
3- Obstructive jaundice
4- Alcohol or drug intake
What are the causes of AST raise but not ALT?
ALT is specific to the liver
ACT increases can be due to:
1- Liver diseases
2- Myocardial infarction (MI)
3- Progressive skeletal muscular dystrophy
4- Crush injury
5- Hemolytic diseases
6- Artifact: in hemolysed samples or if serum separation is delayed.
Caused for decreased serum albumin?
Pregnancy
Decreased amino acids: in diet & reduced synthesis of nonessential amino acids due to either Malnutrition or Malabsorption.
Increased catabolism : Surgery, Trauma, Infections.
Defective synthesis in liver: Chronic liver diseases (liver cirrhosis)
Increased loss : From the kidney (Nephrotic syndrome) or From GIT (Protein loosing enteropathies)
Why would prothrombin time be increased in liver disease?
liver makes prothrombin and other clotting factors
When the PT is high, it takes longer for the blood to clot
Higher PT means liver damage
What happens to AFP (Alpha fetoprotein) in liver disease?
Increases
Can be used to screen and diagnosis hepatocellular carcinoma and hepatoblastoma
What happens to ammonia in liver disease and why?
Ammonia is disposed by formation of urea in liver. hyperammonemia occurs in liver disease and can be toxic to CNS
Causes of hyperammonaemia:
Liver disease:
Gi bleeding - bacteria in GIT on blood urea with production of ammonia
Ornithine transcarbamoylase deficiency (Hereditary)
How would acute cholecystitis present?
Epigastric pain - radiating to the shoulder and in RUQ
Muscle guarding
Positive murphy’s sign (pain present on deep inspiration as well during palpation)
Rebounding tenderness
What is the pathophysiology behind acute cholecystitis
Inflammation of gallbladder secondary to obstruction of gallbladder emptying
Obstruction increases gallbladder secretion -> progressive distention -> compromises vascular supply to gallbladder
Bile stasis irritates mucosa -> inflammation and bacterial growth
What is the presentation and pathophysiology behind Acute/ascending cholangitis?
CHARCOT'S TRIAD - Fever, RUQ pain, Jaundice septic shock (hypotension)
Obstruction of common bile duct (choledocholithiasis) by stones, tumour or trauma leads to this -> biliary stasis and distention
Bacteria can ascend from Ampulla of Vater such as e/coli, klebsiella and enterococcus
Bacteria can enter bloodstream causing sepsis