Which lab is an indicator of cholestasis?

Which lab is an indicator of cholestasis?

• A. Elevated serum alkaline phosphatase
• B. Elevated serum unconjugated bilirubin
• C. Elevated serum conjugated bilirubin > 2 mg/dL
• D. Elevated gamma-glutamyl transferase

Answer: (C)

Cholestasis is indicated by a rise in direct (conjugated) bilirubin in the blood. When bile flow is impaired, bilirubin that has been conjugated in the liver can’t be excreted into the bile ducts and leaks into the bloodstream. Because conjugated bilirubin is water-soluble, it appears in serum and raises the direct bilirubin level, with a value such as >2 mg/dL supporting cholestasis. Unconjugated bilirubin elevation points to prehepatic causes (like hemolysis) or impaired hepatic conjugation, not cholestasis. Alkaline phosphatase and gamma-glutamyl transferase can rise with cholestasis but are less specific single indicators, since they can be influenced by other conditions as well.

Cholestasis is indicated by a rise in direct (conjugated) bilirubin in the blood. When bile flow is impaired, bilirubin that has been conjugated in the liver can’t be excreted into the bile ducts and leaks into the bloodstream. Because conjugated bilirubin is water-soluble, it appears in serum and raises the direct bilirubin level, with a value such as >2 mg/dL supporting cholestasis.

Unconjugated bilirubin elevation points to prehepatic causes (like hemolysis) or impaired hepatic conjugation, not cholestasis. Alkaline phosphatase and gamma-glutamyl transferase can rise with cholestasis but are less specific single indicators, since they can be influenced by other conditions as well.