Neonatology - Neonatal jaundice and kernicterus

Question 1

Definition

Answer 1

Jaundice occurs when excess serum bilirubin deposits in the skin and sclerae. The majority of neonates will have physiological jaundice which is typically harmless and occurs after 24 hours of birth. Pathological jaundice may occur within the first 24 hours or later.

Question 2

Neonatal jaundice can be categorised into:

Answer 2

• Overproduction or impaired conjugation of bilirubin:
  = Kernicterus: unconjugated bilirubin can deposit in the brain, e.g. basal ganglia, causing an encephalopathy
  Hepatocellular disease or biliary obstruction
• Conjugated bilirubin leaks into the blood
  Lack of stercobilin in faeces: pale stools
  Conjugated bilirubin excreted in urine: dark urine

Question 3

Aetiology for overproduction of unconjugated hyperbilirubinaemia

Answer 3

• Physiological jaundice = mild transient rise in bilirubin and always occurs after 24 hours
• Most common cause of neonatal jaundice is due to:
  = Low UGT activity at birth
  = Foetal RBCs have a shorter half life
• Breast milk jaundice = as thought to contain UGT-inhibiting enzymes
• Poor feeding = reduced bowel movements -> increased bilirubin re absorption via the enteropathic circulation
• Sepsis: increases haemolysis + causes cholestasis
• Crigler-Najjar syndrome: genetic deficiency in UGT
• Haemolytic disorders = increased unconj.bili from haem deg.
  = Haemolytic disease of the newborn (e.g. Rhesus disease, ABO incompatibility)
  = Hereditary conditions (e.g. hereditary spherocytosis, G6PD deficiency )
  = Haematoma from birth trauma

Question 4

Conjugated hyperbilirubinaemia Aetiology

Answer 4

• Hepatitis: often idiopathic, but can be congenital HBV infection
• Billiary atresia = resulting in cholestasis
• Cystic Fibrosis = billiary obstruction due to thickened biliary secretions
• Parenteral nutrition
• Dubin Johnson Syndrome: deficiency in the protein which transports conjugated bilirubin into the bile canaliculi
• Congenital hypothyroidism
• Toxins and drugs

Question 5

Epidemiology

Answer 5

• Prematurity
• Male sex
• Low birth weight
• Poor caloric intake
• Family history: previous sibling had neonatal jaundice requiring treatment
• Ethnicity: Asian or American-Indian heritage
• Breastfeeding (formula feeding is protective*)
• Birth trauma
• Maternal age > 25
• Maternal diabetes

Question 6

Features that suggest jaundice is pathological (i.e. not physiological)

Answer 6

• Jaundice in the first 24 hours of life is always pathological
• Conjugated hyperbilirubinaemia is always pathological
• Very high or rapidly rising bilirubin
• Prolonged jaundice (>2 weeks in a term infant and >3 weeks in a preterm infant)
• Systemically unwell neonate
• Poor response to phototherapy

Question 7

Investigation

Answer 7

Transcutaneous bilirubinometry
Serum bilirubin

Question 8

Management

Answer 8

Below phototherapy threshold but < 50μmol/L (5 boxes) below phototherapy threshold:
= Gestational age ≥ 38 weeks and time since birth > 24 hours:
= Repeat serum bilirubin within 18 hours if risk factors present (e.g. sibling with neonatal jaundice)
= Repeat serum bilirubin within 24 hours if no risk factors
FIRST LINE = PHOTOTHERAPY
SECOND LINE = EXCHANGE TRANSFUSION