Bile ductal injury and ductular reaction are frequent phenomena with different significance in autoimmune hepatitis.

Background & Aims The significance of bile duct injury and ductular reaction in biopsies from autoimmune hepatitis patients is not clear. We aim to establish the prevalence and clinical relevance of both phenomena in autoimmune hepatitis. Methods Cases of newly diagnosed, untreated autoimmune hepatitis without overlap syndrome were selected. Pretreatment and follow up biopsies were scored for inflammation, fibrosis, bile ductal injury and ductular reaction. Results Thirty-five cases were studied of whom 14 cases had follow up biopsies. Bile duct injury was present in 29 cases (83%), mostly in a PBC-like pattern and was not correlated with demographical or laboratory findings. Ductular reaction, observed in 25 of 35 cases (71%) using conventional histology and in 30 of 32 cases (94%) using immunohistochemistry, was correlated with portal and lobular inflammation, interface hepatitis and centrilobular necrosis as well as bile duct injury and fibrosis. In 11 of 14 cases (79%) ductular reaction remained present on post-treatment biopsy whereas bile duct injury persisted in six of 14 (43%) of cases. Conclusions Bile duct injury and ductular reaction are very common in newly diagnosed autoimmune hepatitis and cannot be predicted biochemically. Bile duct injury may subside in the majority of treated AIH cases while DR tends to persist during follow up. These findings show that the two phenomena are part of the spectrum of AIH with dissimilar responses to treatment and do not necessarily point towards an overlap syndrome. Persistence of ductular reaction after treatment supports the notion that it represents a regenerative response. [ABSTRACT FROM AUTHOR]