Alkaline phosphatase is another liver enzyme that is frequently measured. This enzyme is usually found in the walls of the bile ducts (tube-like structures within the liver that connect liver cells together). Elevation of alkaline phosphatase may indicate an injury to the biliary cells. Common causes of biliary injury or biliary obstruction (cholestasis) are gallstones and certain medications, although, some of the conditions listed previously can also raise the levels of this enzyme. Alkaline phosphate is also found in the bone and can be elevated in bone diseases. GGT and 5' nucleotidase levels can be elevated in biliary conditions (disease of the gallbladder and bile ducts) along with alkaline phosphatase.
Steatohepatitis (or nonalcoholic fatty liver disease) often is discovered by imaging. This condition may be the most frequent cause of mild liver chemistry elevations and is especially common in patients who are obese, and those who have diabetes or hyperlipidemia. One study 12 of patients referred to a hospital-based gastroenterology practice found that in 83 percent of patients with elevated transaminase levels whose serum evaluation was otherwise negative, liver biopsy revealed steatosis or steatohepatitis. In 10 percent of the patients, however, liver biopsy was normal—a reminder that, at times, mildly elevated transaminase levels do not represent any underlying pathology. Excellent reviews of the management of nonalcoholic fatty liver disease have been published. 13 , 14