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Liver biopsies have consistently contributed to our understanding of the pathogenesis and aetiologies of acute liver disease. As other diagnostic modalities have been developed and refined, the role of biopsy in the management of patients with acute liver failure (ALF), acute‐on‐chronic liver failure (ACLF) and acute hepatitis, including acute liver injury (ALI), has changed. Liver biopsy remains particularly valuable when first‐line diagnostic algorithms fail to determine aetiology. Despite not being identified as a mandatory diagnostic tool in recent clinical guidelines for the management of ALF or ACLF, many centres continue to undertake biopsies given the relative safety of transjugular biopsy in this setting. Several studies have demonstrated that liver biopsy can provide prognostic information, particularly in the context of so‐called indeterminate hepatitis, and is extremely useful in excluding conditions such as metastatic tumours that would preclude transplantation. In addition, its widespread use of percutaneous biopsies in cases of less severe acute liver injury, for example in the establishment of a diagnosis of acute presentation of autoimmune hepatitis or confirmation of a probable or definite drug‐induced liver injury (DILI), has meant that many centres have seen a shift in the ratio of specimens they are receiving from patients with chronic to acute liver disease. Histopathologists therefore need to be equipped to deal with these challenging specimens. This overview provides an insight into the contemporary role of biopsies (as well as explant and autopsy material) in diagnosing acute liver disease. It outlines up‐to‐date clinical definitions of liver injury and considers recent recommendations for the diagnosis of AIH and drug‐induced, autoimmune‐like hepatitis (DI‐AIH). [ABSTRACT FROM AUTHOR]

Background & Aims: Diagnostic histological criteria for autoimmune hepatitis (AIH) have not been clearly established. Previously published criteria focused mainly on chronic AIH, in which inflammatory changes mainly occur in portal/periportal regions and may not be applicable to acute presentation of AIH, in which inflammatory changes are typically predominantly lobular in location. International consensus criteria for the diagnosis and assessment of disease severity in both acute and chronic AIH are thus urgently needed. Methods: Seventeen expert liver pathologists convened at an international workshop and subsequently used a modified Delphi panel approach to establish consensus criteria for the histopathological diagnosis of AIH. Results: The consensus view is that liver biopsy should remain standard for diagnosing AIH. AIH is considered likely, if there is a predominantly portal lymphoplasmacytic hepatitis with more than mild interface activity and/or more than mild lobular hepatitis in the absence of histological features suggestive of another liver disease. AIH is also considered likely if there is predominantly lobular hepatitis with or without centrilobular necroinflammation and at least one of the following features: portal lymphoplasmacytic hepatitis, interface hepatitis or portal‐based fibrosis, in the absence of histological features suggestive of another liver disease. Emperipolesis and hepatocellular rosettes are not regarded as being specific for AIH. Conclusions: The criteria proposed in this consensus statement provide a uniform approach to the histological diagnosis of AIH, which is relevant for patients with an acute as well as a chronic presentation and to more accurately reflect the current understanding of liver pathology in AIH. [ABSTRACT FROM AUTHOR]

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]