Introduction

 

Jaundice occurs in around 60% of newborns. Babies become visibly jaundiced when the bilirubin level reaches 80-120 umol/L.The reasons jaundice is so common is that newborns have a high Hb concentration at birth, their red cell lifespan is only 70 days compared with an adult 120 days and their hepatic metabolism is less efficient in the first few days. However, despite the normal reasons, neonatal jaundice is important as it may be a sign of another disorder and very high levels of unconjucated bilirubin can cause the serious condition of kernicterus.

 

Kernicterus

Kernicterus is an encephalopathy which results from the deposition of unconjugated bilirubin in the basal ganglia and brainstem nuclei. It happens when the levels of unconjugated bilirubin in the blood stream exceeds the albumin-binding capacity of the blood. The free bilirubin is  fat-soluble and can cross the blood-brain barrier and get deposited in the basal ganglia. The level at which this occurs is not clear although keeping the level below 340 umol/L seems to have some consensus as being relatively safe. The effects of this can vary from mild lethargy and poor feeding to irritability, hypertonia, seizures and coma. Surviving infants may have choreoathetoid cerbral palsy, learning difficulties and sensorineural deafness.

 

The Bilirubin pathway

 

Haemoglobin and other haem proteins are broken down into unconjugated bilirubin which is bound to albumin in the blood. In the liver the bilirubin is conjugated by glucuronyl transferase. Conjugated bilirubin is water soluble and passes into the intestines via bile. In the intestines it is either converted to stercobilinogen which is excreted in faeces or it is reabsorbed through the enterohepatic circulation and converted to urobilinogen in the kidneys to be excreted in the urine. Enterohepatic circulation reabsorption is increased when milk intake is low.

 

<24 hours of age

 

This is most commonly caused by haemolysis or congenital infection. It can be serious and needs assessment. Congenital infection usually presents with other signs as well.

 

Haemolytic disorders include:

 

Rhesus incompatibility - Usually identified antenatally by screening of the mother's blood type. Rhesus negative mothers are given anti-D antibodies. To make sense of this condition consider a woman who is A- (that is, rhesus D negative). Naturally she will probably not have antibodies to rhesus D antigens unless she has been previously exposed to rhesus positive blood, causing her body to create antibodies. If this is her first pregnancy and her partner is A+, her baby will have A+ blood type. During the pregnancy there should be no mixing of fetal and maternal blood so there would be no reason for her to develop anti-rhesus antibodies. However at delivery foetal blood may well come into contact with maternal blood causing sensitisation to occur and antibodies to be made. If she then has another rhesus positive baby, these antibodies will 'attack' the baby prenatally. The principle of giving anti-D antibodies to 'at risk' women is to prevent them forming antibodies, therefore preventing the initial sensitisation. This prophylaxis has reduced the prevalence of the condition dramatically but antibodies can still develop to rhesus antigens other than D although this tends to be less severe. If an infant is affected they present with:

 

  • anaemia
  • hydrops (oedema in more than 2 foetal compartments)
  • hepatosplenomegaly with rapidly progressive and severe jaundice

 

ABO incompatibility - Most ABO antibodies are IgM and dont cross the placenta. However some group 'O' mothers have IgG antibodies which do. This can cause haemolysis and therefore jaundice. The newborn's haemoglobin level is usually normal and there is no hepatosplenomegaly. Coomb's test, the direct antibody test, detects antibody on the surface of red cells and will be positive.

 

Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency) - Most common red cell enzymopathy. G6PD is the rate limiting enzyme in the pentose pathway and is essential to prevent oxidative damage to red cells. If red cells lack G6PD they are susceptable to oxidant-induced haemolysis. It is X-linked and so more common in males.

Presentation is with:

  • neonatal jaundice and acute haemolysis in childhood - often precipitated by infection or drugs (some antimalarials and antibiotics)
  • jaundice, pallor and dark urine.

Treatment is usually not needed beyond advice of avoiding precipitants and identifying acute episodes. Diagnosis is by measuring G6PD activity in red cells during an episode

 

Hereditary Spherocytosis - 1 in 5000 caucasian births, usually autosomal dominal inheritance. Due to mutation in genes for skeletal proteins of red cell membrane. This causes the cell to be damaged passing through the spleen and becoming spheroidal and susceptable to destruction in the spleen.

It presents with:

  • jaundice which can be severe but is often intermittent
  • mild anaemia
  • splenomegaly
  • gallstones
  • uncommonly aplastic crisis associated with parvovirus B19 infection.

It can be diagnosed by a blood film and rarely needs management although children should take oral folic acid prophylactically and occasionally require splenectomy.

 

2 days to 3 weeks

 

Physiological jaundice - this is the most common cause of jaundice in this age of onset. It is simply due to the baby adapting to the new environment. It is a diagnosis of exclusion.

 

Breast milk jaundice - The cause for this is unclear. It causes an unconjugated hyperbilirubinaemia and may be increased through dehydration. It will usually settle at around 4-5 weeks and if dehydration has been excluded doesn't need treatment.

 

Other causes - Infection, haemolysis (though this usually presents earlier), polycythaemia and very rarely, Crigler-Najjar syndrome - where there is an abscence of the enzyme glucuronyl transferase.

 

>3 weeks of age

 

This is called 'prolonged or persistent neonatal jaundice'. The cause depends on whether it is unconjugated or conjugated.

 

1. Unconjugated jaudice may be from:

  • breast milk jaundice
  • infection
  • congenital hypothyroidism - this should have been identified during neonatal biochemical screening (Guthrie test).

 

2. Conjugated jaundice may be due to neonatal hepatitis syndrome, or biliary atresia:

 

Biliary atresia - This is when the baby has an absent or destroyed biliary system.

 

It presents with conjugated jaundice, dark urine and pale stools. They may have bruising, pallor and hepato- and/or splenomegaly. Testing involves ultrasound of the bile ducts and gallbladder and a radioisotope scan with TBIDA which will show good uptake by the liver but no excretion into the bowel. Liver biopsy will show fibrosis and hepatitis. Treatment is a hepatoportoenterostomy. This involves surgical bypass of the damaged duct and anastamosis of the jejunum to the patent ducts. If the procedure happens at less than 60 days of age 80% of children will achieve bile drainage. If the procedure fails, liver transplantation will be needed. Cirrhosis and portal hypertension can occur later in life even when the procedure is successful. Early identification and treatment of this condition is vital.

 

Treatment of Congenital Jaudice

 

The need for treatment in congenital jaundice should be assessed according to the severity of the jaundice (be careful not to under-estimate in non-caucasians), the rate at which the jaundice is changing (it tends to follow a linear progression then plateau) gestational age, and any other clinical problems such as prematurity.

 

Management is to ensure dehydration and poor intake are corrected. Phototherapy with 450nm wavelength blue-green light converts unconjugated bilirubin into harmless water-soluble pigment. The infants eyes should be protected as the light can by painful. If this isn't successful or the jaundice is severe, exchange transfusion can be done where twice the infant blood volume is exchanged. This procedure has some associated morbidity and mortality and should not be a first line therapy.

 

Possible OSCE stations

Possible OSCE Stations might be:

 

Please examine and discuss your investigation and management plan for a 5 hour old baby who presents with jaundice. Take a proper paediatric history - conception, gestation, problems during pregnancy, birth - type, weight, complications. Ask about feeding and activity level. Ask about family history. When asked to examine, try not to hone in on the one sign. Assess the baby as a whole. Make sure you assess dehydration - wet nappies, central capilliary refill and general conscious level. Consider your investigations in reference to the most common causes of jaundice in that age group. Have a low threshold for treatment in babies with other issues such as prematurity.

 

You are a GP, a parent comes in with her 3 and half week old baby who has jaundice which is not settling. The key to this sort of station is a good history. You need to know the story from conception to now. Post-partum you need to know when the jaundice started, what investigations have already been done and how the baby is generally. You need to know how the baby is fed and if there are any family history issues. Likelihood is that this sort of station will either be: a sick baby (e.g. biliary atresia), or a breast fed baby who is well (breast milk jaundice). You need to counsel the mother appropriately and come up with a relevant management plan (or monitoring plan in the case of breast milk jaundice).

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