Direct bilirubin (DBil), also known as conjugated bilirubin, is produced by the combination of indirect bilirubin with glucuronic acid under the action of glucuronosyltransferase in the liver.Direct bilirubin is soluble in water, reacts directly with azo reagent, and can be excreted through the kidney with urine.The liver plays an important role in the metabolism of bilirubin, including the uptake, binding and excretion of indirect bilirubin in the blood by hepatocytes.The increase of serum direct bilirubin indicates that the excretion of bilirubin from the biliary tract is blocked after treatment by hepatocytes.The direct determination of bilirubin is helpful to the diagnosis and differential diagnosis of jaundice.
Chinese name
Conjugated bilirubin
Foreign name
Direct Bilirubin，DBIL
reference value
0-6.8 μmol/L
Unconjugated gallbladder
1.7-10.2μmol/L
total bilirubin
Adult 3.4~17.1 μ mol/L
significance
Obstructive jaundice, hepatocellular jaundice
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The certification expert of this term is
Yang Tiesheng|Chief physician
Laboratory Department of Peking University People's Hospitalto examine
Direct bilirubin increase: mainly seen in obstructive jaundice, hepatocellular jaundice, liver cancer, pancreatic head cancer, cholelithiasis, cholangiocarcinoma, etc.
The differential diagnosis of jaundice type is as follows:
1. Hemolytic jaundice: after the destruction of red blood cells, a large amount of hemoglobin enters monocyte macrophages and is converted into indirect bilirubin.Due to the excess of indirect bilirubin, hepatocytes cannot convert all indirect bilirubin into direct bilirubin, resulting in the increase of indirect bilirubin in serum.
2. Hepatocellular jaundice: liver lesions lead to the decline of the ability of hepatocytes to transform indirect bilirubin, so the serum intermediate bilirubin increases.And because the bile capillaries are blocked, the excretion of direct bilirubin from the biliary tract is blocked, and the direct bilirubin in the serum will also increase.
3. Obstructive jaundice: due to intrahepatic or extrahepatic obstruction, the excretion of direct bilirubin from the biliary tract is blocked, which can only enter the blood circulation, resulting in the increase of direct bilirubin in serum.
Normal value reference range
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Normal reference value of serum direct bilirubin: 0 ～ 6.8 μ mol/L.
