Jaundice
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}} Jaundice, also known as icterus (attributive adjective: "icteric"), is a yellowing of the skin, sclera (the white of the eyes) and mucous membranes caused by increased levels of bilirubin in the human body. 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.
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Causes of jaundice
When red blood cells die, the heme in their hemoglobin is converted to bilirubin in the spleen and in the kupffer cells in the liver. 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 (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 sickle cell anemia and glucose 6-phosphate dehydrogenase deficiency can lead to increase red cell lysis and therefore hemolytic jaundice. Defects in bilirubin metabolism also present as jaundice. Jaundice usually comes with high fevers.
Hepatic
Hepatic causes include acute hepatitis, hepatotoxicity and alcoholic liver disease. Whereby cell necrosis reduces the liver's ability to metabolise and excrete bilirubin leading to a build up in the blood. 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
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 and dark urine suggests an obstructive or post-hepatic cause as normal feces get their colour from bile pigments. Patients sometimes also complain of itching.
Neonatal jaundice
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}} Neonatal jaundice is usually harmless: this condition is often seen in infants 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 often treated with bili lights, exposing them to high levels of colored light to break down the bilirubin. This works due to a photo oxidation process occurring on the bilirubin in the subcutaneous tissues of the neonate. Light energy creates isomerization of the bilirubin and consequently transformation into compounds that the new born can excrete via urine and stools. Blue light is typically used for this purpose. Green light is more effective at breaking down bilirubin, but is not commonly used because it makes the babies appear sickly, which is disturbing to observers.
Brief exposure to indirect sunlight each day and increased feeding are also helpful. A newborn should not be exposed to direct sunlight because of the danger of sunburn, which is much more harmful to a newborn's thin skin than that of an adult.
"Breastfeeding jaundice" occurs in more than 10% of breastfed infants, caused by insufficient milk intake. More rarely, "breast milk jaundice" occurs in about 0.5% of babies during the second or third week, caused by high levels of beta-glucuronidase in breast milk. Neither condition is a reason to stop nursing, though in these cases caregivers usually advise supplements to breastfeeding to ensure the baby is not dehydrated.
A small percentage of infants will have "hemolytic jaundice". The infant's red blood cells will be broken down quicker because of antibodies that attack the infant's red blood cells are transferred from the mother to the baby's bloodstream. The antibodies may be due to ABO (blood group) incompatibility or Rhesus factor differences. 1
With high doses of bilirubin (severe hyperbilirubinemia) there can be a complication known as kernicterus. This is the chief reason for neonatal jaundice to be treated. The effects of kernicterus range from fever, seizures, and a high-pitched crying to mental retardation. This is due to a staining effect on the basal ganglia leading to neuronal damage.
In neonates, jaundice tends to develop because of two factors - the breakdown of fetal hemoglobin as it is replaced with adult hemoglobin and the relatively immature hepatic metabolic pathways which are unable to conjugate bilirubin as fast as an adult.
All jaundice should be medically evaluated before treatment can be given. If the neonatal jaundice does not clear up with simple phototherapy, other causes such as biliary atresia should be considered.
See also
- Gilbert's syndrome, a genetic disorder of bilirubin metabolism which can result in mild jaundice, which is found in about 5% of the population.cs:Žloutenka
da:Gulsot de:Ikterus es:Ictericia eo:Iktero fr:Ictère it:Ittero he:צהבת ms:Demam kuning jaundis nl:Geelzucht ja:黄疸 pl:Żółtaczka (medycyna) pt:Icterícia sl:Hiperbilirubinemija sv:Gulsot zh:黄疸