Nonalcoholic Fatty Liver Disease vs. Nonalcoholic Steatohepatitis: Pathological and Clinical Implications.

The implications and prognosis of nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH) are substantially different. The aim of the present review is to describe and compare the pathological and clinical implications of these two conditions. Patients with NASH have a higher risk of progressing to cirrhosis than patients with NAFL but without steatohepatitis, who tend to have a non-progressive disease and only a minority progresses to NASH. Patients with NASH also are at greater risk to develop hepatocellular cancer (HCC) and NASH is the third commonest cause of HCC. In contrast, only few cases of HCC have been reported in patients with isolated NAFL. Given that nonalcoholic fatty liver disease is the hepatic manifestation of metabolic syndrome, it is also strongly related to cardiovascular disease (CVD). Again, it appears that patients with NASH have higher cardiovascular risk than patients with NAFL. Finally, all-cause mortality is also higher in patients with NASH than in patients with NAFL; mortality rates in the latter patients do not differ from the general population. In conclusion, NAFL and NASH have different prognosis and therefore it is imperative to develop accurate, noninvasive methods that will identify the presence of steatohepatitis in this population.