Histologic spectrum of nonalcoholic fatty liver disease in morbidly obese adolescents

Background & Aims: To characterize the spectrum of nonalcoholic fatty liver disease (NAFLD) in morbidly obese adolescents, we correlated liver histology with clinical features and compared findings with reported adult data. We hypothesized that NAFLD would be less severe as a result of younger age and shorter duration of obesity, but portal inflammation and fibrosis would be more prevalent. Methods: Cross-sectional study was made of 41 adolescent subjects, 13-19 years old (mean, 16 years), 61% female, 83% non-Hispanic white, mean body mass index 59 kg/m(2), undergoing gastric bypass with liver biopsy. Liver biopsies were graded and staged as proposed by the NASH Clinical Research Network. Data were analyzed by using descriptive statistics, analysis of variance, and Fisher exact tests. Results: Eighty-three percent had NAFLD: 24% steatosis alone, 7% isolated fibrosis with steatosis, 32% nonspecific inflammation and steatosis, and 20% nonalcoholic steato-hepatitis (NASH). Twenty-nine percent had fibrosis; none had cirrhosis. Abnormal ALT (P = .05) and AST (P = .01) were more prevalent in NASH. Mean fasting glucose was significantly higher in NASH (P = .05), but prevalence of the metabolic syndrome was not significantly different. Conclusions: NAFLD was very prevalent in morbidly obese adolescents, but severe NASH was uncommon. In contrast to morbidly obese adults, lobular inflammation, significant ballooning, and perisinusoidal fibrosis were rare, whereas portal inflammation and portal fibrosis were more prevalent, even in those who did not meet criteria for NASH. These findings might support use of a modified scoring system for pediatric NASH. Presence of the metabolic syndrome in morbidly obese adolescents did not distinguish NASH from steatosis alone.