Liver, Hepatocyte - Glycogen Accumulation and Depletion

In the absence of any treatment-related changes within a study, the degrees of glycogen demonstrated in Figure 1, Figure 2, and Figure 3 are considered background (spontaneous) changes and should not be diagnosed. If, in contrast to the control animals, there is a treatment-related increase in glycogen in the hepatocytes, glycogen accumulation should be diagnosed in the treated animals and assigned a severity grade. Likewise, if there is a treatment-related glycogen depletion (as in Figure 4 vs. Figure Figure 3), glycogen depletion should be diagnosed in the treated animals and given a severity grade. In the context of a toxicity study, some treated animals may have a depressed appetite and will have decreased amounts of glycogen in the liver, in contrast to the concurrent controls. Consequently, interpretation of glycogen depletion should take food consumption and general animal health into consideration.

Changes in the amount of hepatocellular glycogen are frequently accompanied by other cytoplasmic alterations, such as fatty change or cytoplasmic vacuolization, and alterations in glycogen content can be difficult to distinguish from the accompanying changes. In those situations, a diagnosis of hepatocyte cytoplasmic vacuolization is appropriate, along with a severity grade, but the morphology of the cytoplasmic changes in the hepatocytes should be thoroughly described in the pathology narrative. The pathology narrative should also include the pathologist’s opinions regarding the contents of the cytoplasmic vacuoles.