DIAGNOSIS AND INTERPRETATION OF STEATOSIS AND STEATOHEPATITIS

Steatosis-accumulation of triacylglycerol in hepatocytes-is a common f inding in liver biopsy specimens. The commonest form is macrovesicular change, which occurs in response to a wide range of insults. In the a bsence of other features, the pathologist cannot ascertain the likely cause on morphological features alone but can give an indication of th e severity of steatosis. Close clinicopathological correlation is requ ired to establish the cause. In most instances, macrovesicular steatos is is at least potentially reversible. Although it may be thought of a s a benign condition, it may be associated with the development of nec roinflammation and fibrosis-so-called steatohepatitis, The classic exa mple of this is alcoholic hepatitis, but there is increasing awareness of steatohepatitis occurring in nonalcoholics: NASH. Distinction betw een alcoholic hepatitis and NASH on purely histological grounds may be impossible; careful clinicopathological discussion is mandatory, Micr ovesicular steatosis is generally a more severe disease than the macro vesicular form and is seen in a variety of conditions in which there i s either an inherited or an acquired defect in P-oxidation of fatty ac ids; the former includes mitochondrial cytopathies and disorders of ur eagenesis, and the latter includes acute fatty liver of pregnancy and Reye's syndrome. This review describes the morphological features of s teatosis and steatohepatitis, considers their pathogenesis, and outlin es the clinical significance of the different patterns of injury. Copy right (C) 1998 by W.B. Saunders Company.