Health Tips and Tricks

Since the advent of routine automated serum testing, a common problem in gastroenterology has been the determination of the cause, and thus the importance, of abnormalities in liver chemistries. At first, such evaluations may be frustrating because of the lack of any well-defined diagnostic algorithms. However, armed with an understanding of the diverse panel of available measurements of liver function and serum markers of hepatobiliary disease and knowledge of the patterns by which specific hepatobiliary disorders typically present themselves, the clinician can usually approach these diagnostic challenges in an orderly and selective manner. The normal values of certain laboratory tests that either lead to or assist in diagnosis are listed in Table 8-1 with ranges or reference intervals in traditional and Système International d’Unités (SI).
Drug-induced abnormalities in liver chemistries are frequently encountered. Although familiarity with the hepatic side effects of all drugs used is not possible, knowledge of the potential for and clinical pattern of
hepatotoxicity of commonly used agents is extremely useful. Representative drugs and their typical pattern of hepatic injury are listed in Table 8-2.
A thorough occupational history may provide important clues to an otherwise cryptic case of abnormal liver chemistries. A representative list of industrial and environmental hepatotoxins is provided in Table 8-3.
Elevated serum aminotransferase levels can be observed among patients with any type of liver disease, and among patients with cardiac and skeletal muscle disorders. All too commonly, serum aminotransferase elevations are incorrectly ascribed to alcoholic liver injury. Alternative diagnoses, such as autoimmune hepatitis, viral and drug-induced hepatitis, nonalcoholic steatohepatitis, hemochromatosis, Wilson disease, and a1-antitrypsin deficiency, should always be considered. In alcoholic liver disease, serum aspartate aminotransferase (AST; SGOT) and alanine aminotransferase (ALT; SGPT) levels are typically less than 300 units/L, and the ratio of AST to ALT is greater than 2 (Fig. 8-1). In the case of acetaminophen hepatotoxicity involving a patient with alcoholism, this ratio is maintained. In this setting the serum aminotransferase elevation is striking, reaching and often exceeding levels typically associated with toxic, ischemic, or viral injury (Fig. 8-2).
Elevation of serum alkaline phosphatase levels occurs primarily in cholestatic disorders, but the degree of elevation does not help one differentiate extrahepatic from intrahepatic causes. In the face of findings inconsistent with extrahepatic obstruction, intrahepatic cholestasis, whether drug-induced or from disorders such as primary biliary cirrhosis, as well as infiltrative processes, such as tuberculosis, sarcoidosis, and metastatic carcinoma, should be considered. The differential diagnosis of granulomatous processes involving the liver that may present with infiltrative features is quite extensive. A partial listing of some of these disorders is provided in Table 8-4.