Changes in histological criteria lead to different prevalences of nonalcoholic steatohepatitis in severe obesity.

The worldwide obesity epidemic contributes to the increasing incidence of a number of diseases, as nonalcoholic fatty-liver disease (NAFLD) and its most severe form, the nonalcoholic steatohepatitis (NASH). Data on the prevalence of NASH has varied from 18.5%(5) to 69%(43 )in obesity, an unacceptable wide range. The aim of our study was to evaluate how prevalence of NASH is influenced by the different diagnostic histological criteria. Consecutive assessment of 325 obese patients referred for bariatric surgery (BMI >or = 35 kg/m(2)), 146 of whose were submitted to histological analysis of the liver allowed the evaluation of the prevalence of NAFLD. Steatohepatitis was diagnosed histologically using 3 types of criteria: a) broad criteria, where steatosis was associated with at least 2 of the following parameters: any degree of lobular inflammatory infiltrate, hepatocellular ballooning and perisinusoidal/ perivenular fibrosis; b) restricted criteria, where the hepatocellular ballooning was of moderate or severe intensity; c) ultrarestricted criteria, which required perisinusoidal and/or perivenular fibrosis. NAFLD was present in 111 (76%) of the patients, and the prevalence of NASH was 25.3% when ultrarestricted criteria were used, 41.1% with restricted criteria and 55.5% with broad criteria. In conclusion, more accurate definition of the criteria for histological diagnosis of NASH should be required, so that further clinicopathological studies may define the long-term progression of the disease and evaluate therapeutic strategies.