Science Fair Project Encyclopedia
Jaundice, technically 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. Jaundice comes from the French word jaune, meaning yellow. Jaundice also causes itchiness of the skin.
Causes of jaundice
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 (or hemolytic) jaundice is caused by anything which causes an increased rate of hemolysis (breakdown of red blood cells). In tropical countries, malaria can cause jaundice in this manner. Certain genetic diseases, such as glucose 6-phosphate dehydrogenase deficiency can lead to increase red cell lysis and therefore hemolytic jaundice. Defects in bilirubin metabolism also present as jaundice.
Hepatic causes include acute hepatitis , hepatotoxicity and alcoholic liver disease. Less common causes include primary biliary cirrhosis, Gilbert's syndrome and metastatic carcinoma . Jaundice commonly seen in the newborn baby is another example of hepatic jaundice.
Post-hepatic (or obstructive) jaundice, also called cholestasis, 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 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 jaundice are typically treated with bili lights, exposing them to high levels of blue light to break down the bilirubin. Brief exposure to indirect sunlight each day and breastfeeding are also helpful. You do not want to expose a newborn to direct sunlight because of the danger of sunburn, which is much more harmful to a newborns thin skin than that of adults. Bilirubin has a toxic effect on the brain known as kernicterus. That is the chief reason for neonatal jaundice to be treated.
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.
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.
The steroids in the breastmilk act as antagonists to the enzymes that break down the red blood cells. This usually occurs after the first two weeks of life.
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details