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Hepatobiliary Notes

Medicine Notes > Paediatrics Notes

This is an extract of our Hepatobiliary document, which we sell as part of our Paediatrics Notes collection written by the top tier of University Of Nottingham students.

The following is a more accessble plain text extract of the PDF sample above, taken from our Paediatrics Notes. Due to the challenges of extracting text from PDFs, it will have odd formatting:

Hepatobiliary

Physiology of Bilirubin Production

*

The breakdown product of Hb is unconjugated bilirubin

o

Insoluble in water but soluble in lipids

*

Carried in the blood bound to albumin

*

When albumin binding is saturate unconjugated bilirubin can cross the blood brain barrier (lipid soluble)

*

Unconjugated bilirubin bound to albumin is taken up by the liver and conjugated by action of glucuronyl transferase

*

o

Water soluble and excreted in bile into the gut

o

Detectable in urine when blood levels rise (urobilinogen)

o

Excreted in faeces as stercobilinogen

Reabsorption of bilirubin from the gut (enterohepatic circulation) is increased when milk intake is low

Jaundice

*

Clinically jaundice when bilirubin levels are >80 umol/L

*

Over 50% of newborns will become visibly jaundice because:

o

Marked physiological release of Hb from the breakdown of red cells due to the high concentration of Hb at birth

o

RBC life span is half that of adults (70 Vs. 120 days)

o

Hepatic bilirubin metabolism is less efficient

Kernicterus

*

Encephalopathy resulting from the deposition of unconjugated bilirubin in the basal ganglia and brainstem nuclei

*

Occurs when albumin binding is saturated and the lipid soluble unconjugated bilirubin can cross the BBB

*

Acute lethargy and poor feeding

*

Severe irritability , increased muscle tone (baby will lie with arched back [opisthotonos]), seizures and coma

*

Sequalae choreoathetoid cerebral palsy, learning difficulty, SNHL

Causes of Neonatal Jaundice

*

Starting at <24h of age

o

Haemolytic disorders resultant rise in unconjugated bilirubinRh incompatabilityABO incompatabilityG6PD deficiency

?
o

Spherocytosis, pyruvate kinase deficiency conjugated bilirubin. Infants have other abnormal clinical signs (growth

Congenital infection

restriction, hepatosplenomegaly and thrombocytopenia purpura)

*

*

At 24h to 2 weeks of age

o

Physiological jaundice

o

Breast milk jaundice

o

Infection

o

Haemolysis

o

Bruising

o

Polycythaemia

o

CriglerNajjar syndrome UDPglucuronosyltransferase (UGT) is absent

Jaundice at >2 weeks of age (>3 weeks if prem)

o

o

UnconjugatedPhysiological or breast milk most common, gradually fades by 45 weeksInfection (UTI)HypothyroidHaemolyticHigh GI obstruction (pyloric stenosis)

Conjugated (>25umol/L) PRESENTS pale stools and dark urine (possible hepatomegaly and poor weight gain)?

Bile duct obstruction cholestatic (obstructive jaundice)

*

Biliary atresia

*

Choledochal cyst

Neonatal hepatitis intrahepatic jaundice hepatocyte damage and cholestasis (mixed conjugated and unconjugated)

Investigations

*

Measure bilirubin with a transcutaneous bilirubinometer when:

o

Gestation age >35 weeks

o

Postnatal age of >24 hours

*

If levels are >250umol/L check the result by measuring serum bilirubin

*

Always use serum bilirubin measurements in babies:

o

<35 weeks gestational age

o

Who have jaundice within the first 24 hours of life

Management

*

Phototherapy

o

(Blue) Light of 450nm converts unconjugated bilirubin into harmless water soluble pigmento

Excreted in the urine

Guidelines vary typically after 48 hours of life start phototherapy at 100umol/L less than transfusion level (360400umol/L) around 260umol/L

*

o

Check bilirubin in 6 hours

o

ComplicationsTemperature instabilityMacular rash and bronze discolouration of the skin in conjugated jaundice

Exchange Transfusion

o

Required if the levels of bilirubin rise to a dangerous level

o

Twice the infants blood volume is transfused*

Blood screened to exclude CMV, hep B and C, HIV

o

No level known to be safe in Rh disease bilirubin <340umol/L prevents kernicterus

o

Exhange indicated if:Bilirubin >400umol/L at termRises quickly (>10umol/L per hour)Or baby is unwell

In Rh or ABO incompatibility use Ig

Haemolytic Disorders

*

*

*

Diagnostic clues to haemolysis are:

o

Raised reticulocyte (immature red cells with no nucleus) count

o

Unconjugated bilirubinaemia and increased urinary urobilinogen

o

Abnormal appearance of red cells on blood film

o

Positive direct antiglobulin test (Coomb's) detects antibody coated red cells

o

Increased red blood cell precursors in bone marrow

Rhesus haemolytic disease

o

Severely affected may develop fetal hydrops with oedema and ascites (hepatosplenomegaly)

o

Incidence has fallen since introduction of antiD immunisation

ABO incompatability

o

Most ABO antibodies are IgM and do not cross the placenta

o

Some group O women have IgA antiAhaemolysin which can cross the placenta and haemolyse the RBCs of group A babies

*

o

Occasionaly same may occur for group B

o

Severity is typically less than that of Rh incompatability, hepatosplenomegaly is absent

o

Direct antibody test (Coomb's test) is positive

o

Jaundice peaks in 1272 hours

G6PD deficiency

o

High prevalence in individuals originating from the Mediterranean, Middle East / Far East and Central Africa

o

X linked and therefore predominantly affects males

o

Lack of this enzyme leads to oxidant induced haemolysis

o

Clinically

oNeonatal jaundiceFever, malaiseDark urine

Acute haemolysis may be precipitated by:InfectionCertain drugso

*

*

Antimalarials

*

Sulphonamides, quinolones and nitrofuratoin

*

Aspirin

Fava beans

Diagnosis made by measuring G6PD activity in RBCs

Spherocytosis

o

1 in 5000 caucasian birthds

o

Autosomal dominant Family history

o

Mutations in genes for proteins in the red cell membrane (spectrin, ankyrin or band 3)

o

Destroyed in the microvasculature of the spleen (extravascular haemolysis)

o

Clinical Features may includeJaundice (severe haemolytic jaundice in first few days of birth)Mild anaemia in childhoodSplenomegaly

oAplastic crisis transient caused by parvovirus B19Gallstones

Diagnosis Identified by recognising spherocytes on blood filmo

Exclude haemolysis with a direct (Coomb's) antibody test

ManagementMild chronic anaemia folic acidSplenectomy may be considered for poor growth or troublesome symptoms

*Deferred until 7 years

Apaplastic crisis transfusion

Prolonged Jaundice

*

In babies of a gestational age >37 weeks 14 dys

*

Gestational age <37 weeks 21 days

*

Unconjugated

*

o

Physiological or breast milk most common, gradually fades by 45 weeks

o

Infection (UTI)

o

Hypothyroid

o

Haemolytic

o

High GI obstruction (pyloric stenosis)

Conjugated (>25umol/L) PRESENTS pale stools and dark urine (possible hepatomegaly and poor weight gain)

o

o

Bile duct obstruction cholestatic (obstructive jaundice)Biliary atresiaCholedochal cyst

Neonatal hepatitis

intrahepatic jaundice

hepatocyte damage and cholestasis (mixed

conjugated and unconjugated)

*

In preterm and term babies with prolonged jaundice:

o

Look for pale chalky stools and/or dark urine that stains the nappy

o

Measure the conjugated bilirubin

o

Carry out a full blood count, blood group determination, direct antiglobulin test and urine culture

o

Ensure that routine metabolic screening has been performed.

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