Bilirubin is formed in the reticuloendothelial system during the degradation of aged erythrocytes. The heme portion from hemoglobin and from other heme‑containing proteins is removed, metabolized to bilirubin, and transported as a complex with serum albumin to the liver. In the liver, bilirubin is conjugated with glucuronic acid for solubilization and subsequent transport through the bile duct and elimination via the digestive tract. Diseases or conditions which, through hemolytic processes, produce bilirubin faster than the liver can metabolize it, cause the levels of unconjugated (indirect) bilirubin to increase in the circulation. Liver immaturity and several other diseases in which the bilirubin conjugation mechanism is impaired cause similar elevations of circulating unconjugated bilirubin. Bile duct obstruction or damage to hepatocellular structure causes increases in the levels of both conjugated (direct) and unconjugated (indirect) bilirubin in the circulation.
SI units Conversion Calculator. Convert Bilirubin, Direct level to mmol/l, µmol/l, mg/dl, mg/100ml, mg%, mg/l, µg/ml. Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for Bilirubin, Direct unit conversion to mmol/l, µmol/l, mg/dl, mg/100ml, mg%, mg/l, µg/ml.