Which lab finding is most specific for biliary obstruction?

Which lab finding is most specific for biliary obstruction?

• A. Gamma-Glutamyl Transferase (GGT)
• B. Alkaline phosphatase
• C. Serum albumin
• D. Serum ammonia

Answer: (B)

Biliary obstruction causes cholestasis, which stimulates the bile duct epithelium to release alkaline phosphatase into the bloodstream. Because ALP is produced by cells in the bile ducts, its level rises prominently when bile flow is blocked, making it the most characteristic single lab finding among the options for indicating biliary obstruction. Gamma-glutamyl transferase can also be elevated with hepatobiliary disease, but ALP directly reflects the obstruction pattern. Serum albumin and serum ammonia reflect liver synthetic function and overall hepatic failure rather than obstruction, so they’re not as informative for detecting a blocked bile duct.

Biliary obstruction causes cholestasis, which stimulates the bile duct epithelium to release alkaline phosphatase into the bloodstream. Because ALP is produced by cells in the bile ducts, its level rises prominently when bile flow is blocked, making it the most characteristic single lab finding among the options for indicating biliary obstruction. Gamma-glutamyl transferase can also be elevated with hepatobiliary disease, but ALP directly reflects the obstruction pattern. Serum albumin and serum ammonia reflect liver synthetic function and overall hepatic failure rather than obstruction, so they’re not as informative for detecting a blocked bile duct.