Jaundice and Cholestasis (inc causes) Flashcards
What are the two major functions of bile?
Emulsification of dietary fat through detergent action of bile salts
Elimination of bilirubin, excess cholesterol, xenobiotics and other waste products that aren’t hydrophilic (can’t enter urine)
Can both conjugated and unconjugated bilirubin accumulate systemically?
Yes
How hydrophilic is unconjugated bilirubin?
Virtually not at all
Cannot be excreted by the kidneys even at high serum concentrations
If unconjugated bilirubin isn’t complexed with albumin in the blood for transport, what complications does it cause?
Can diffuse into tissues, and in newborns/foetuses can cross the BBB causing neuronal toxicity
Thus in haemolytic disease of the newborn (erythroblastosis foetalis) unconjugated bilirubin accumulates in the developing brain causing severe neurological damage (kernicterus)
What are the potential outcomes of kernicterus?
Acute bilirubin encephalopathy (ABE)
Chronic bilirubin encephalopathy (CBE)
Subtle bilirubin encephalopathy (SBE)
Describe acute bilirubin encephalopathy
Lethargy
Hypertonia or hypotonia
High pitched cry
Fever
Seizures
Death
Describe chronic bilirubin encephalopathy’s symptoms
Movement disorders (cerebral palsy or dystonia)
Auditory neuropathy
Oculomotor impairments (nystagmus, strabismus, and/or corticovisual impairment)
Impaired digestive function
Describe subtle bilirubin encephalopathy’s symptoms
Mild forms of the same symptoms of chronic bilirubin encephalopathy
Can acute bilirubin encephalopathy be treated?
Yes
Reduce bilirubin levels and symptoms will reduce and no sequelae should result
Can chronic or subtle bilirubin encephalopathy be treated?
Hyperbilirubinaemia can be treated, but not the neuronal damage
What is the protein that normally conjugates bilirubin?
Uridine diphosphate glucuronosyltransferase isoform 1A1 (UGT1A1)
Is UGT1A1 active in the foetus/newborn?
No, inactive
Though levels are the same as in the maternal liver
Why is hyperbilirubinaemia dangerous in the foetus/newborn?
UGT1A1 inactive (maternal liver performs this function for the foetus) and is inactive several months after birth
BBB not complete, can cross into the brain
Is jaundice in a newborn a negative prognostic marker?
Not normally
New research shows that physiologic jaundice is within the reference range in the first week of life for healthy term babies, particularly those breastfed
What areas of the brain does unconjugated bilirubin typically enter?
Cranial nerve nuclei
Basal ganglia
Hippocampus
Cerebellum can also be affected
How can hyperbilirubinaemia be treated?
Exchange transfusion if not refractory to treatment (replacing baby’s blood with citrate phosphate dextrose (CPD) banked O- (important because all antibodies may not be removed) blood that does not contain bilirubin
Phototherapy
What is the mortality rate of exchange transfusion in the treatment of hyperbilirubinaemia kernicterus?
3 in 1000 (high)
Which conditions can lead to unconjugated hyperbilirubinaemia?
Excess production of bilirubin (hapmolytic anaemia, ineffective erythropoiesis eg pernicious anaemia or thalassaemia)
Reduced hepatic uptake (drug interference with membrane carrier systems)
Impaired conjugation (physiologic jaundice of the newborn, breast milk, Crigler-Najjar type I and II, Gilbert Syndrome, diffuse liver disease eg cirrhosis)
Which conditions can lead to conjugated hyperbilirubinaemia?
Deficiency of canalicular membrane transporters (Dubin-Johnson syndrome, Rotor syndrome)
Impaired bile flow
What is the primary pathology in Crigler-Najjar syndrome?
Absent UGT1A1 activity in Type I
Decreased UGT1A1 activity in Type II
How does conjugated bilirubin differ from unconjugated bilirubin?
Water soluble
Nontoxic
Only loosly binds to albumin
Does conjugated bilirubin ever much bind to albumin?
In prolonged conjugated hyperbilirubinaemia there is a fraction that binds to albumin
This is called the bilirubin delta fraction
What are the normal serum bilirubin levels in a normal adult?
0.3 - 1.2 mg/dL
With what bilirubin levels does jaundice typically become noticeable?
2.0 - 2.5 mg/dL
What are the 5 mechanisms by which jaundice can develop?
Excessive extrahepatic production of bilirubin
Reduced hepatocyte uptake
Impaired conjugation
Decreased hepatocellular excretion
Impaired bile flow
Can you have both conjugated and unconjugated bilirubin in excess?
Yes
Typically only occurs though when conjugated hyperbilirubinaemia is present first
Mechanism unknown, could be from competition for hepatic clearance between conjugated and unconjugated
Is it useful to know the serum bilirubin level of both conjugated and unconjugated?
No
Typically only one will be raised and that is the one that you must investigate to investigate the cause
What is the normal survival time for babies with Criggler-Najjar syndrome type I (absent UGT1A1) that are not given a liver transplant?
18 months
What happens to unconjugated bilirubin in individuals with Crigler-Najjar syndrome type II?
UGT1A1 that is present is only able to convert bilirubin to monoglucuronidated bilirubin
How is Crigler-Najjar syndrome type II treated?
Phenobarbitals can induce hypertrophy of the endoplasmic reticulum
Exchange transfusion
Phototherapy
How is phototherapy effective in the treatment of jaundice?
Causes the formation of water-soluble bilirubin isomers that can be secreted in bile without conjugation
What is the efficacy of phototherapy dependant on?
Dose, ie:
Duration of being under the light (don’t go towards the light)
Intensity of the light
Age
Amount of skin exposed to the light