What are serum bilirubin level findings suggestive of extrahepatic biliary obstruction?

Updated: Oct 16, 2019
  • Author: Jennifer Lynn Bonheur, MD; Chief Editor: Vinay Kumar Kapoor, MBBS, MS, FRCS, FAMS  more...
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This is typically associated with considerable direct and indirect bilirubin elevation. However, in the early phases of obstruction and with incomplete or intermittent obstruction, serum bilirubin levels may only be mildly elevated. Initially, an increase in the conjugated bilirubin level occurs without affecting the unconjugated bilirubin level because obstruction of the CBD prevents excretion of already conjugated bilirubin into the duodenum. Conjugated bilirubin that does reach the intestine is deconjugated by intestinal bacteria. Unconjugated bilirubin, in contrast to the conjugated form, easily crosses the intestinal epithelial barrier into the blood. It accumulates in the blood because the uptake mechanism and the hepatic cells are overburdened by bilirubin that has already been conjugated but cannot be excreted. Therefore, indirect bilirubin levels rise even in persons with obstructive jaundice.

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