Jaundice

Jaundice is not a disease, but rather a sign that can occur in many different diseases. Jaundice is the yellowish staining of the skin and sclerae (the whites of the eyes) that is caused by high levels in blood of a chemical bilirubin. The color of the skin and the whites of the eyes vary depending on the level of bilirubin. When the bilirubin level is mildly elevated, they are yellowish. When the bilirubin level is high, they tend to be brown.

Bilirubin comes from red blood cells. When red blood cells get old, they are destroyed by the body. Hemoglobin, the iron-containing chemical in the red blood cells that carries oxygen, is released from the destroyed red blood cells after the iron it contains is removed. The chemical that remains in the blood after the iron is removed becomes bilirubin.

The liver has many functions. One of its functions is to produce and secrete bile into the intestines to help digest dietary fat. Another function is to remove toxic chemicals or waste products from the blood, and bilirubin is a waste product. The liver removes bilirubin from the blood. After the bilirubin has entered the liver cells, the cells conjugate (attaching other chemicals, primarily glucuronic acid) to the bilirubin, and then secrete the bilirubin/glucuronic acid complex into bile. The complex that is secreted in bile is called conjugated bilirubin. The conjugated bilirubin travels in the bile to the intestine and is eliminated in the feces. (Bilirubin is what gives feces its brown color.) Conjugated bilirubin is different from the bilirubin that is released from the red blood cells and not yet removed from the blood. The latter is termed unconjugated bilirubin.

Jaundice occurs when there is:

1. too much bilirubin being produced for the liver to remove from the blood (for example, patients with hemolytic anemia have an abnormally rapid rate of destruction of their red blood cells that releases large amounts of bilirubin into the blood);
2. a defect in the liver that prevents bilirubin from being removed from the blood, converted to bilirubin/glucuronic acid (conjugated) or secreted in bile; or
3. blockage of the bile ducts that decreases the flow of bile and bilirubin from the liver into the intestines. For example, the bile ducts can be blocked by cancer, gallstones, or inflammation of the bile ducts. The decreased conjugation, secretion, or flow of bile that can result in jaundice is referred to as cholestasis: however, cholestasis does not always result in jaundice.

Source: MedicineNet.com
http://www.medicinenet.com/jaundice/article.htm