What is 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 the chemical bilirubin. The color of the skin and sclerae 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. Hemoglobin, the iron-containing chemical in 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 the liver's functions is to produce and secrete bile into the intestines to help digest dietary fat. Another 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 is eliminated in the feces. (Bilirubin is what gives feces its brown color.) Conjugated bilirubin is distinguished from the bilirubin that is released from the red blood cells and not yet removed from the blood which is termed unconjugated bilirubin.

What causes jaundice?
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,

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 cancers, 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

Symptoms and Diagnosis
Jaundice usually appears around the second or third day of life. It begins at the head and progresses downward. A jaundiced baby's skin will usually appear yellow first on the face, followed by the chest and stomach, and finally, the legs. It can also cause the whites of an infant's eyes to appear yellow.
Since many babies are now released from the hospital at 1 or 2 days of life, it is best for the baby to be seen by a doctor within 1 to 2 days of leaving the hospital to check for jaundice. Parents should also keep an eye on their infants to detect jaundice.
If you notice your baby’s skin or eyes looking yellow you should contact your child's doctor to see if significant jaundice is present.
At the doctor's office, a small sample of your infant's blood can be tested to measure the bilirubin level. Some offices use a light meter to get an approximate measurement, and then if it is high, check a blood sample. The seriousness of the jaundice will vary based on how many hours old your child is and the presence of other medical conditions.

How is jaundice treated?

With the exception of the treatments for specific causes of jaundice mentioned previously, the treatment of jaundice usually requires a diagnosis of the specific cause of the jaundice and treatment directed at the specific cause, e.g., removal of a gallstone blocking the bile duct

Blood group incompatibility (Rh or ABO problems): if a baby has a different blood type than the mother, the mother might produce antibodies that destroy the infant's red blood cells. This creates a sudden buildup of bilirubin in the baby's blood. Incompatibility jaundice can begin as early as the first day of life. Rh problems once caused the most severe form of jaundice, but now can be prevented with an injection of Rh immune globulin to the mother within 72 hours after delivery, which prevents her from forming antibodies that might endanger any subsequent babies.