Final answer:
Jaundice is detectable when blood bilirubin levels reach about 2 mg/100 ml. It causes yellow discoloration of the skin and eyes due to the diffusion of bilirubin into tissues. Elevated levels of bilirubin, especially in newborns, can be dangerous and are treated with phototherapy.
Step-by-step explanation:
Jaundice becomes visible when the concentration of bilirubin in the blood reaches approximately 2 mg/100 ml. At this level, the blood cannot hold any more bilirubin, resulting in its diffusion into the tissues, and causing a yellow discoloration.
Normally, bilirubin concentration in the blood is less than 1 mg/100 ml. Hyperbilirubinemia is the term for elevated bilirubin levels, and it is particularly concerning in newborns due to their underdeveloped blood-brain barrier and the high neurotoxicity of bilirubin. When unconjugated bilirubin exceeds a level of 25 mg/100 ml in infants, it can lead to a dangerous condition known as 'kernicterus'.
Treatment for hyperbilirubinemia often involves phototherapy, as UV light assists in breaking down bilirubin rapidly. Jaundice can be caused by various factors, such as liver malfunction due to damage, alcoholism, infections, or obstruction in bile flow. Tests are available to diagnose jaundice, including the Van Den Bergh test, which measures levels of conjugated bilirubin.