Jaundice, otherwise known as icterus, is yellowing of the skin, sclera (eyes) and mucous membranes caused by increased levels of bilirubin in the system. Usually the concentration of bilirubin in the blood must exceed 2-3mg/dL for the coloration to be easily visible.
Causes of jaundice
When red blood cells die, the heme in their hemoglobin is converted to bilirubin. The bilirubin is processed by the liver, enters bile and is eventually excreted through feces.
Consequently, there are three different classes of causes for jaundice. Pre-hepatic or hemolytic causes, where too many red blood cells are broken down, hepatic causes where the processing of bilirubin in the liver does not function correctly, and post-hepatic or extrahepatic causes, where the removal of bile is disturbed.
Pre-hepatic
Pre-hepatic jaundice is caused by anything which causes an increased rate of haemolysis (breakdown of red blood cells). In tropical countries, malaria can cause jaundice in this manner. Defects in bilirubin metabolism also present as jaundice.
Hepatic
Hepatic causes include acute hepatitis, drug toxicity and alcoholic liver disease. Less common causes include primary biliary cirrhosis, cholestasis of pregnancy and metastatic carcinoma.
Posthepatic
Post-hepatic jaundice is caused by an interruption to the drainage of bile in the biliary system. The most common causes are gallstones in the common bile duct and pancreatic cancer in the head of the pancreas. Other causes include strictures of the common bile duct, ductal carcinoma, pancreatitis and pancreatic pseudocysts. A rare cause of obstructive jaundice is Mirizzi's syndrome.
The presence of pale stools suggests an obstructive or post-hepatic cause as normal feces get their colour from bile pigments.
Neonatal jaundice
Neonatal jaundice is usually harmless: this condition is often seen in babies around the second day after birth, lasting till day 8 in normal births, or to around day 14 in premature births. Serum bilirubin normally drops to a low level without any intervention required: the jaundice is presumably a consequence of metabolic and physiological adjustments after birth. Infants with neonatal jaudice are typically treated by exposing them to high levels of blue light which breaks down the bilirubin. Brief exposure to direct sunlight each day and breastfeeding are also helpful.
In neonates, jaundice tends to develop because of two factors - the breakdown of fetal hemoglobin as it is replaced with "normal" hemoglobin and the relatively immature hepatic metabolic pathways which are unable to conjugate bilirubin as fast as an adult.
If the neonatal jaundice does not clear up with simple phototherapy, other causes such as biliary atresia should be considered.
Breastfeeding jaundice
A not well understood cause of jaundice is breastfeeding, which is a diagnosis of exclusion (i.e. exclude any dangerous causes of jaundice first), is harmless and resolves on cessation of breastfeeding. Worried mothers can trial their baby on formula feeds for a few days to see if the jaundice ebbs while continuing to express milk so nursing can resume later.
