5' nucleotidase is used to investigate the origin of increased serum alkaline phosphatase. It is a liver-related enzyme used to work up cholestatic/biliary obstruction. It parallels the increases of alkaline phosphatase and leucine aminopeptidase in hepatobiliary diseases, but is not usually elevated in skeletal disorders such as Paget disease of bone. It is increased with metastatic neoplasia in liver and in primary biliary cirrhosis, biliary obstruction from calculi and tumor.