What is the role of alkaline phosphatase (ALP) measurement in the workup of 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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Answer

A membrane-bound enzyme localized to the bile canalicular pole of hepatocytes, ALP is markedly elevated in persons with biliary obstruction. However, high levels of this enzyme are not specific to cholestasis. To determine whether the enzyme is likely to be of hepatic origin, measure gamma-glutamyl transpeptidase (GGT) or 5-prime-nucleotidase. These values tend to parallel the ALP levels in patients with liver disease. GGT is used most commonly. While it is part of the routine evaluation of biliary obstruction, the degree of elevation of ALP cannot be used to reliably discriminate between extrahepatic and intrahepatic causes of biliary obstruction.


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