A Case Oriented Approach to Profiling the Liver I and II

A CASE ORIENTED APPROACH TO PROFILING THE LIVER I AND II

Overview
The liver performs a wide variety of different and seemingly unrelated functions. For example, it plays a central role in plasma protein synthesis, carbohydrate metabolism, lipid metabolism, and detoxification of both endogenous and exogenous substances. In addition, the liver is the site of bilirubin metabolism and bile synthesis, as well as synthesis of most circulating coagulation factors. The Kuppfer cells of the hepatic sinusoids form one of the major elements of the monocyte-macrophage continuum (mononuclear phagocyte system).
The diversity of hepatic function suggests that a chemistry organ panel assessing the liver must also be diverse. The screening panel includes tests of primary importance as well as a group of additional tests to be more closely evaluated when abnormalities are present in any of the screens.

Primary Hepatic Panel Serum
Alanine Aminotransferase (ALT)
Serum alanine aminotransferase (ALT) is probably the most accurate indicator of liver disease in small animal medicine. However, it is important to realize that ALT is not a liver function test but rather an indicator of hepatocyte injury. ALT is a liver-specific enzyme present in high concentrations within the cytoplasm of hepatic parenchymal cells. As such, serum ALT activity is obviously increased with necrosis. However, a common response to non-lethal hepatocellular injury involves membrane blebbing with subsequent release of cytoplasmic-rich vesicles such that increased ALT activity is seen in the serum. Therefore, in a general way, the degree of elevation correlates not with the severity of hepatocellular damage but rather with the number of hepatocytes involved. In other words, diffuse fatty change may result in more extreme ALT activity elevations than focal hepatic necrosis. […]