In obstructive jaundice, which bilirubin fraction is predominantly elevated?

In obstructive jaundice, which bilirubin fraction is predominantly elevated?

• A. Conjugated Bilirubin
• B. Unconjugated Bilirubin
• C. Delta Bilirubin
• D. Bilirubin Dimers

Answer: (A)

When bile flow is blocked, bilirubin that has been conjugated in the liver cannot be excreted into the intestine and instead accumulates in the blood. The conjugated (direct) form is water-soluble, so it rises in the serum and is excreted in urine, producing jaundice with dark urine. Unconjugated bilirubin, which is not water-soluble, does not rise primarily unless there is another process like hemolysis or impaired hepatic uptake. Delta bilirubin can be elevated with long-standing obstruction, but the predominant elevation in obstructive jaundice is the conjugated bilirubin.

When bile flow is blocked, bilirubin that has been conjugated in the liver cannot be excreted into the intestine and instead accumulates in the blood. The conjugated (direct) form is water-soluble, so it rises in the serum and is excreted in urine, producing jaundice with dark urine. Unconjugated bilirubin, which is not water-soluble, does not rise primarily unless there is another process like hemolysis or impaired hepatic uptake. Delta bilirubin can be elevated with long-standing obstruction, but the predominant elevation in obstructive jaundice is the conjugated bilirubin.