This article describes the diagnostic tests and treatments for jaundice in babies.
- Introduction to jaundice
- What is jaundice?
- Physiological jaundice in babies
- First day jaundice
- Measuring jaundice levels in babies
- Phototherapy treatment for jaundice in babies
- Prolonged jaundice in babies
- What is conjugated hyperbilirubinaemia?
The word jaundice is derived from the French word for yellow, which is “jaune”. Jaundice refers to yellow discolouration of the skin and mucous membranes in newborn infants. It is a common condition that affects 60% of term and 80% of preterm babies in the first week of life. Jaundice can be either normal “physiological” or abnormal “pathological”. Pathological jaundice can, if not detected and treated appropriately, lead to brain damage in newborn infants. For this reason all health professionals who deal with newborn babies are trained to look out for jaundice.
Jaundice results from the deposition of a yellow substance called bilirubib in the skin and mucus membranes. Bilirubin is produced from the breakdown of Haemoglobin. This type of Bilirubin is called “unconjugated” or “indirect” Bilirubin. It is carried by the bloodstream to the liver where it is metabolised into “conjugated” or “direct” bilirubin and subsequently excreted in the stools. It is this conjugated bilirubin which gives stools its yellow or brown colour. Some of the conjugated bilirubin in the gut is reabsorbed back into the bloodstream and this process is called the entero-hepatic circulation. Bilirubin is carried in the blood attached to albumin (a type of protein) molecules. This is because bilirubin molecules are fat soluble which means they do not dissolve in water and therefore cannot be filtered out and excreted through the kidneys.
Jaundice occurs when there is excessive production of bilirubin or inadequate metabolism in the liver. If the bilirubin level in the blood is extremely high, bilirubin molecules can cross over from the blood into the brain and deposit in the brain tissues (in a specific area of the brain called the Globus Pallidus). This will lead to brain damage and this condition is called “Kernicterus”. Kernicterus is extremely rare nowadays due to advances in antenatal and postnatal medical management of women and their at-risk babies.
Newborn babies are at risk of getting normal physiological jaundice because:
a. They are born with a high level of haemoglobin leading to excessive breakdown and therefore excessive production of bilirubin.
b. They have a slower metabolism, circulation and excretion of bilirubin.
Physiological jaundice appears on the second or third day of life and normally disappears by day ten of life and is completely harmless. Breast fed babies are more likely to develop physiological jaundice in the first week of life. This may be related to inadequate intake of breast milk leading to sluggish gut action and therefore an increase in the entero-hepatic circulation. It is therefore very important for breast feeding mothers to receive professional advice, support and assessment particularly during the first week after birth.
Jaundice on the first day of life is always pathological and must not be ignored. A baby who develops jaundice on the first day of life must be examined by an experienced doctor and have blood tests done to check the level of bilirubin and look for other causes of early jaundice which include:
a. Excessive breakdown of haemoglobin which may result from Blood Group or Rhesus incompatibility between mother and baby.
b. Infection in the baby.
There are devices available to measure the bilirubin level non-invasively (without needing to do a blood test). These are called Bilimeters and they measure the degree of jaundice of the skin by pressing a sensor on the baby’s forehead. Bilimeters can be used on babies of all racial backgrounds and all colours. Bilimeters should only be used in term babies who are more than 24 hours old. Preterm babies and babies who are jaundiced during the first day must have a blood test to measure the level of bilirubin. A Bilimeter reading is plotted on a chart. If the reading is low, it saves a baby from having to have a heel pricked to enable a blood sample to be taken. However, if a Bilimeter reading is borderline high or high, the baby must have a blood test to measure the exact level of bilirubin. The blood bilirubin level is plotted on a chart according to baby’s gestation and age. If the blood bilirubin reading is above treatment line on the chart, phototherapy (light treatment) should be started.
The idea of phototherapy started in Essex in the UK in 1957 when a nursing sister at the Neonatal Unit at Rochford Hospital noticed that body areas exposed to sunlight were less yellow compared to covered areas. She recognised that sunlight had bleached jaundiced skin. This finding was reported to Dr R. J. Cremer who conducted a study which showed that exposing jaundiced newborns to sunlight reduced their bilirubin level. We now know that it is the blue spectrum of light that is effective at reducing bilirubin levels in the blood. Phototherapy emits blue (not ultraviolet as is commonly assumed) light onto exposed areas of a baby’s skin. Blue light has a wavelength that falls into the centre of bilirubin’s absorption spectrum. Blue light passes through the exposed skin and changes the structure of a bilirubin molecule from a fat-soluble to a water-soluble form which can then be excreted in the urine. Phototherapy is known to be a very effective and safe method of treating babies with newborn jaundice in the first week of life.
The length of phototherapy treatment is normally between 24 and 72 hours and usually takes place in a hospital. When phototherapy treatment stops, altered (water soluble) bilirubin molecules that have not been excreted through the urine will change back to their original form of fat soluble molecules and increase the blood bilirubin level. This is known as rebound hyperbilirubinaemia. Babies receiving phototherapy should have as much as possible of their skin exposed to blue light. The conventional way of delivering phototherapy is through a blue light device placed one meter away from the baby. The eyes are normally covered in order to protect them against any possible damaging side effects of blue light. Babies under phototherapy must take extra fluids in order to prevent dehydration as a result of prolonged exposure to phototherapy. Minor and manageable side effects of phototherapy include diarrhoea, rash and dehydration.
Jaundice lasting for more than 14 days after birth is termed prolonged jaundice. This is more common in breast fed babies and is called “Breast Milk Jaundice”. The exact mechanism through which breast milk leads to prolonged jaundice is not clearly understood. Breast Milk Jaundice is completely harmless and breast feeding should continue despite the jaundice. However Breast Milk Jaundice is a diagnosis by exclusion. This means that there is no specific test to confirm a diagnosis of Breast Milk Jaundice and other possible causes for prolonged jaundice need to be excluded. If no other causes are found in a jaundiced baby who is breast fed, a diagnosis of Breast Milk Jaundice can be made. Other conditions that can cause prolonged jaundice include liver diseases, thyroid diseases, blood conditions, genetic conditions or infections.
Conjugated bilirubin levels in the blood are normally less than 10% of the total bilirubin. A high level of conjugated bilirubin must always be investigated urgently as there is a specific time window for intervention in certain conditions.
The presence of pale stools and dark urine may indicate a liver condition known as Biliary Atresia. This is a disease that causes obstruction of the bile ducts outside the liver. This leads to blockage in the drainage of conjugated bilirubin from the liver and therefore a high level of conjugated bilirubin in the blood. Bilirubin gives stools their dark colour. The blockage of bilirubin excretion from the liver into the gut leads to pale stools. The high level of conjugated bilirubin in the blood leads to excessive excretion of conjugated bilirubin in the urine and a dark urine colour. The treatment for Biliary Atresia is a surgical operation to relieve the obstruction. However, surgery must be performed within four to six weeks after birth in order to achieve better chances of success.
Jaundice is a common condition in newborn babies and in most cases will cause no harm. Health professionals need to understand this condition so that the few babies who are at risk of developing serious complications can be identified and treated promptly.