Jaundice, (also known as icterus, attributive adjective: icteric) is a yellowish discoloration of the skin, the conjunctival membranes over the sclerae (whites of the eyes), and other mucous membranes caused by hyperbilirubinemia (increased levels of bilirubin in the blood). This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluids. Typically, the concentration of bilirubin in the plasma must exceed 1.5 mg/dL[1] ( > 35 micromoles/L), three times the usual value of approximately 0.5 mg/dL[1], for the coloration to be easily visible. Jaundice comes from the French word jaune, meaning yellow.
One of the first tissues to change color as bilirubin levels rise in jaundice is the conjunctiva of the eye, a condition sometimes referred to as scleral icterus. However, the sclera themselves are not "icteric" (stained with bile pigment) but rather the conjunctival membranes that overlie them. The yellowing of the "white of the eye" is thus more properly conjunctival icterus.[2]
Signs and symptoms
Eyes
It was once believed persons suffering from the medical condition jaundice saw everything as yellow. By extension, the jaundiced eye came to mean a prejudiced view, usually rather negative or critical. Alexander Pope, in "An Essay on Criticism" (1711), wrote: “All seems infected that the infected spy, As all looks yellow to the jaundiced eye.”[3] Similarly in the mid-19th century the English poet Alfred Lord Tennyson wrote in the poem “Locksley Hall”: “So I triumphe'd ere my passion sweeping thro' me left me dry, left me with the palsied heart, and left me with a jaundiced eye.”
Differential diagnosis
When a pathological process interferes with the normal functioning of the metabolism and excretion of bilirubin just described, jaundice may be the result. Jaundice is classified into three categories, depending on which part of the physiological mechanism the pathology affects.
Pre-hepatic
Laboratory findings include:
- Urine: no bilirubin present, urobilirubin > 2 units (except in infants where gut flora has not developed).
- Serum: increased unconjugated bilirubin.
- Kernicterus is associated with increased bilirubin
Hepatic
Hepatic jaundice causes include acute hepatitis, hepatotoxicity and alcoholic liver disease, whereby cell necrosis reduces the liver's ability to metabolize and excrete bilirubin leading to a buildup in the blood. Less common causes include primary biliary cirrhosis, Gilbert's syndrome (a genetic disorder of bilirubin metabolism which can result in mild jaundice, which is found in about 5% of the population), Crigler-Najjar syndrome, metastatic carcinoma and Niemann-Pick disease, type C. Jaundice seen in the newborn, known as neonatal jaundice, is common, occurring in almost every newborn as hepatic machinery for the conjugation and excretion of bilirubin does not fully mature until approximately two weeks of age.
Laboratory findings include:
Urine: Conjugated bilirubin present, urobilirubin > 2 units but variable (except in children). Kernicterus is a condition not associated with increased bilirubin.