Jaundice is a yellow color to the skin and/or eyes caused by an increase in bilirubin in the bloodstream. Bilirubin is a yellow substance formed when hemoglobin (the part of red blood cells that carries oxygen) is broken down as part of the normal process of recycling old or damaged red blood cells. Bilirubin is carried in the bloodstream to the liver and processed so that it can be excreted out of the liver as part of bile (the digestive fluid produced by the liver). Bilirubin processing in the liver involves attaching it to another chemical substance in a process called conjugation.
Processed bilirubin in the bile is thus called conjugated bilirubin.
Unprocessed bilirubin is called unconjugated bilirubin.
Bile is transported through the bile ducts into the beginning of the small intestine (duodenum). If bilirubin cannot be processed and excreted by the liver and bile ducts quickly enough, it builds up in the blood (hyperbilirubinemia). As bilirubin levels in the blood increase, the whites of the eyes turn yellow first, followed by the skin. During the first week of life, the majority of full-term newborns develop unconjugated hyperbilirubinemia, often causing jaundice that normally resolves within a week or two (physiologic jaundice). Jaundice caused by unconjugated hyperbilirubinemia is even more common among premature infants.
Bile is transported through the bile ducts into the beginning of the small intestine (duodenum). If bilirubin cannot be processed and excreted by the liver and bile ducts quickly enough, it builds up in the blood (hyperbilirubinemia). The excess bilirubin settles in the skin, the whites of the eyes, and other tissues, causing them to turn yellow (jaundice).
Complications of jaundice
Whether jaundice is dangerous depends on
What causes the jaundice
How high the bilirubin level is
Whether the bilirubin is conjugated or unconjugated
Some disorders that cause jaundice are dangerous whatever the bilirubin level is. Extremely high unconjugated bilirubin levels regardless of cause are dangerous.
The most serios consequence of high unconjugated bilirubin levels is
Kernicterus
Kernicterus is brain damage due to accumulation of bilirubin in the brain. The risk of this disorder is higher for newborns who are premature, who are seriously ill, or who are given certain drugs. If untreated, kernicterus may lead to significant brain injury resulting in developmental delay, cerebral palsy, hearing loss, seizures, and even death. Although now rare, kernicterus still occurs, but it can nearly always be prevented by early diagnosis and treatment of hyperbilirubinemia. Once brain injury has occurred, there is no treatment to reverse it.
