Jaundice is not actually a disease, but a condition that is caused by an elevated amount of the bile pigment bilirubin in the blood. The normal bilirubin level in blood serum is between 0.2 and 1.2 mg/dL. If the concentration rises to above 3 mg/dL, jaundice can develop as a yellow discoloration of the skin or the whites of the eyes. The buildup of bilirubin in the blood can be caused by a variety of different disorders.
Bilirubin is a yellow pigment produced from hemoglobin in red blood cells. At end of their life span, red blood cells travel to the spleen, where they are broken down and their hemoglobin is converted into bilirubin by a series of biochemical reactions. The bilirubin is transported to the liver, where it is conjugated (attached) to another molecule, making it water soluble. It then moves on to the gall bladder as a component of bile. Bile is released into the intestines through the common bile duct during digestion. Eventually, the bilirubin is excreted from the body through the feces or else reabsorbed by the intestines, transported to the kidneys and excreted through the urine.
There are three categories of jaundice, depending on which part of the bilirubin metabolic pathway is affected.
Pre-hepatic jaundice, also known as unconjugated or hemolytic jaundice, is caused by a disorder that occurs before the bilirubin reaches the liver. Hemolytic disorders increase the rate of red blood cell destruction so that bilirubin is produced faster than it can be processed by the liver and excreted. Some examples of hemolytic diseases are malaria, sickle cell anemia, and other hereditary red blood cell and small blood vessel disorders. Other causes of pre-hepatic jaundice include immune reactions, kidney failure, and enlargement of the spleen.
Hepatic or hepatocellular jaundice occurs if the condition is within the liver. Some causes are inflammation of the liver due to viral hepatitis B and C, alcoholic liver disease with cirrhosis, genetic diseases, drug reactions and liver cancer.
Post-hepatic jaundice, also called obstructive or cholestatic jaundice, results when there is a blockage in the bile ducts preventing the bilirubin to travel from the gallbladder to the intestines. This type of jaundice is often caused by gallstones in the biliary ducts. It can also result from pancreatic cancer.
Neonatal jaundice is common in newborn infants, particularly if they are premature, because the liver is not yet fully functional. Phototherapy, exposing the infant to bright light for short periods of time each day, helps to change the bilirubin into a harmless form. It is important to carefully monitor the bilirubin levels in newborns, because the bilirubin can cause brain damage if the levels are too high for an extended period of time.
The treatment of jaundice depends on its underlying cause. Laboratory tests can help to determine where in the metabolic pathway the problem is located, and the treatment would address the specific disease, such as malaria or viral hepatitis. Treatment of obstructive jaundice may require surgical removal of gallstones, or even the gallbladder or pancreas. If the liver is damaged by alcoholism or abuse of drugs, it may begin to heal and regenerate once the harmful substance is no longer present.
References:
http://www.ahealthyme.com/article/gale/100083576
http://www.britannica.com/EBchecked/topic/301639/jaundice
http://en.wikipedia.org/wiki/Jaundice
http://www.enotes.com/nursing-encyclopedia/jaundice
