A variety of diagnostic tests help doctors assess disorders of the liver, gallbladder, and biliary tract (the ducts that connect the liver and gallbladder and that transport bile). Among the most important are a group of blood tests known as liver function tests. However, the term is somewhat misleading because most such tests do not test the metabolic or bile-secreting functions of the liver. Rather, they detect inflammation of or damage to the liver. Such blood tests represent a noninvasive way to screen for the presence of liver disease (for example, hepatitis in blood donations) and to measure the severity and progress of liver disease and its response to treatment.

Depending on the suspected problem, a doctor may also order certain imaging tests, such as ultrasound, computed tomography (CT), or cholangiography of the bile ducts using magnetic resonance imaging (MRI) or x-rays. Also, a doctor may take a sample of liver tissue for examination under a microscope, a procedure called a liver biopsy.

Liver Function Tests Liver function tests are performed on blood samples and measure levels of enzymes and other substances produced by the liver. These substances include Alanine transaminase (ALT) Albumin Alkaline phosphatase Alpha-fetoprotein Aspartate transaminase (AST) Bilirubin Gamma-glutamyl transpeptidase Lactic dehydrogenase Mitochondrial antibodies 5'-Nucleotidase Levels of some of these substances measure how well the liver performs its normal functions of making proteins and secreting bile. Levels of other substances detect the presence and degree of liver inflammation. One test of liver function is the prothrombin time (PT), which is used to calculate the International Normalized Ratio (INR). Both the PT and the INR are measures of the time needed for blood to clot.

Last full review/revision October 2006 by Eldon A. Shaffer, MD