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Jaundice (Bilirubin Metabolism (Fate of urobilinogen (Excreted by kidneys,…
Jaundice
Bilirubin Metabolism
Bilirubin is conjugated in the liver with glucuronic acid. This makes it water soluble
Conjugated bilirubin is secreted into bile and passes into the gut
Porphyrin is converted to unconjugated bilirubin which is taken up by the liver
Some conjugated bilirubin is taken up again by the liver due to enterohepatic circulation
Haem is broken down into prophyrin and iron
In the gut, conjugated bilirubin is converted to urobilinogen by bacteria
Haemoglobin is broken down into globin and haem
Fate of urobilinogen
Excreted by kidneys
Converted to stercobilin - this colours faeces brown
Reabsorbed by kidneys
Conjugated Hyperbilirubinaemia
Less conjugated bilirubin enters the gut and the faeces becomes pale
In severe cases, it is associated with intracable pruritus which is treated by relief of obstruction
As conjugated bilirubin is water soluble, it is excreted into urine making it dark.
Classification
Hepatic
Caused by liver disease
Post-hepatic
Caused by bile duct obstruction
Causes of hepatic jaundice
Cirrhosis
Liver mets or abscesses
Alcohol excess
Haemachromatosis
Drugs e.g. paracetamol, statins, rifampicin
Syphilis
Viruses e.g. hepatitis, EBV
Signs of hepatic + post hepatic jaundice
Pale stools
Maybe itching
Dark urine
Abnormal liver tests
Causes of post-hepatic jaundice
Common bile duct gallstones
Pancreatic cancer
Primary sclerosing cholangitis
Compression of bile duct
Drugs e.g. flucloxacillin, steroids, the pill, sulfonylureas
Mirizzi's syndrome
Primary biliary cirrhosis
Investigations
Urine analysis: bilirubin is absent in pre-hepatic causes, urobilinogen is absent in obstructive jaundice
FBC, cblood film, reticulocyte count, Coombs' test, malaria parasites
Examine for signs of chronic liver disease, lymphadenopathy, hepatomegaly, splenomegaly, ascites
Ultrasound of bile ducts, liver and pancreas for masses
Ask about blood transfusions, IV drug use, body piercings, tattoos, sexual activity, travel, family history, alcohol use, medications
Liver biopsy
Unconjugated Hyperbilirubinaemia
Causes
Impaired Hepatic Uptake
Drugs e.g. contrast agents, rifampicin
Right heart failure
Impaired conjugation
Gilbert's syndrome - congenital metabolic dysfunction
Crigler-Najjar - congenital, mutation in enzyme
Overproduction
Haemolysis e.g. malaria, DIC
Infeffective erythropoiesis
Physiological neonatal jaundice
As bilirubin is not soluble in water, it does not enter the urine
All unconjugated jaundice is pre-hepatic
Signs of Pre-Hepatic Jaundice
Normal stools
No itching
Normal urine
Normal liver tests
Treatment
Hydrate
Broad spectrum antibiotics in obstruction
Treat underlying cause
Monitor for ascites + encephalopathy
Definition
60 umol/L
Jaundice Classification
Site of problem
Hepatocellular
Pre-hepatic
Post-hepatic
Type of circulating bilirubin
Conjugated
Unconjugated
= Yellowing of skin, sclerae and mucosae due to increased plasma bilirubin