Severe acute liver disease in adults: Contemporary role of histopathology.

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).

Long-term Outcome of Asymptomatic Patients With Graft Fibrosis in Protocol Biopsies After Pediatric Liver Transplantation.

BACKGROUND: The histological prevalence of allograft fibrosis in asymptomatic children after liver transplantation (LT) is well documented. However, long-term graft and patient survival remain unclear. This retrospective multicenter study aims to determine the prevalence of allograft fibrosis and analyze the long-term outcome for patients transplanted in childhood. METHODS: We reviewed clinical data of children who had undergone 10-y protocol liver biopsies. We excluded patients with autoimmune hepatitis, primary sclerosing cholangitis, hepatitis B or C, and retransplantation. In total, 494 patients transplanted in childhood across 12 international transplant centers were included. We evaluated the development of fibrosis by comparing the results with biopsies obtained 5 and 15 y post-LT. Histological findings were correlated with graft and patient survival up to 20 y post-LT. RESULTS: In the 10-y biopsies, periportal or pericentral fibrosis was observed in 253 patients (51%), 87 (18%) had bridging fibrosis, 30 (6%) had cirrhosis, and 124 (25%) had no fibrosis. The prevalence and stage of graft fibrosis significantly progressed from 5 to 10 y. At 10 y, the severity of fibrosis correlated significantly with inflammation. Patients with graft cirrhosis in the 10-y biopsy were more likely to die or require retransplantation subsequently ( P = 0.027). CONCLUSIONS: At 10 y post-LT, most patients transplanted in childhood developed fibrosis, based on the protocol liver biopsies. Although mild-to-moderate graft fibrosis did not largely affect patient or graft survival up to 20 y post-LT, this progressive fibrosis finding has substantial implications for developing cirrhosis and portal hypertension in adult care.

Survey of liver pathologists to assess attitudes towards digital pathology and artificial intelligence.

AIMS: A survey of members of the UK Liver Pathology Group (UKLPG) was conducted, comprising consultant histopathologists from across the UK who report liver specimens and participate in the UK National Liver Pathology External Quality Assurance scheme. The aim of this study was to understand attitudes and priorities of liver pathologists towards digital pathology and artificial intelligence (AI). METHODS: The survey was distributed to all full consultant members of the UKLPG via email. This comprised 50 questions, with 48 multiple choice questions and 2 free-text questions at the end, covering a range of topics and concepts pertaining to the use of digital pathology and AI in liver disease. RESULTS: Forty-two consultant histopathologists completed the survey, representing 36% of fully registered members of the UKLPG (42/116). Questions examining digital pathology showed respondents agreed with the utility of digital pathology for primary diagnosis 83% (34/41), second opinions 90% (37/41), research 85% (35/41) and training and education 95% (39/41). Fatty liver diseases were an area of demand for AI tools with 80% in agreement (33/41), followed by neoplastic liver diseases with 59% in agreement (24/41). Participants were concerned about AI development without pathologist involvement 73% (30/41), however, 63% (26/41) disagreed when asked whether AI would replace pathologists. CONCLUSIONS: This study outlines current interest, priorities for research and concerns around digital pathology and AI for liver pathologists. The majority of UK liver pathologists are in favour of the application of digital pathology and AI in clinical practice, research and education.

Standardizing the histological assessment of late posttransplantation biopsies from pediatric liver allograft recipients.

Excellent short-term survival after pediatric liver transplantation (LT) has shifted attention toward the optimization of long-term outcomes. Despite considerable progress in imaging and other noninvasive modalities, liver biopsies continue to be required to monitor allograft health and to titrate immunosuppression. However, a standardized approach to the detailed assessment of long-term graft histology is currently lacking. The aim of this study was to formulate a list of histopathological features relevant for the assessment of long-surviving liver allograft health and to develop an approach for assessing the presence and severity of these features in a standardized manner. Whole-slide digital images from 31 biopsies obtained ≥4 years after transplantation to determine eligibility for an immunosuppression withdrawal trial were selected to illustrate a range of typical histopathological findings seen in children with clinically stable grafts, including those associated with alloantibodies. Fifty histological features were independently assessed and, where appropriate, scored semiquantitatively by six pathologists to determine inter- and intraobserver reproducibility of the histopathological features using unweighted and weighted kappa statistics; the latter metric enabled distinction between minor and major disagreements in parameter severity scoring. Weighted interobserver kappa statistics showed a high level of agreement for various parameters of inflammation, interface activity, fibrosis, and microvascular injury. Intraobserver agreement for these features was even more substantial. The results of this study will help to standardize the assessment of biopsies from long-surviving liver allografts, aid the recognition of important histological features, and facilitate international comparisons and clinical trials aiming to improve outcomes for children undergoing LT.

Consensus recommendations for histological criteria of autoimmune hepatitis from the International AIH Pathology Group: Results of a workshop on AIH histology hosted by the European Reference Network on Hepatological Diseases and the European Society of Pathology: Results of a workshop on AIH histology hosted by the European Reference Network on Hepatological Diseases and the European Society of Pathology.

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.

Banff consensus recommendations for steatosis assessment in donor livers.

BACKGROUND AND AIMS: No consensus criteria or approaches exist regarding assessment of steatosis in the setting of human donor liver suitability for transplantation. The Banff Working Group on Liver Allograft Pathology undertook a study to determine the consistency with which steatosis is assessed and reported in frozen sections of potential donor livers. APPROACH AND RESULTS: A panel of 59 pathologists from 16 countries completed a questionnaire covering criteria used to assess steatosis in donor liver biopsies, including droplet size and magnification used; subsequently, steatosis severity was assessed in 18 whole slide images of donor liver frozen sections (n = 59). Survey results (from 56/59) indicated a wide variation in definitions and approaches used to assess and report steatosis. Whole slide image assessment led to a broad range in the scores. Findings were discussed at a workshop held at the 15th Banff Conference on Allograft Pathology, September 2019. The aims of discussions were to (i) establish consensus criteria for defining "large droplet fat" (LDF) that predisposes to increased risk of initial poor graft function and (ii) develop an algorithmic approach to determine fat droplet size and the percentage of hepatocytes involved. LDF was defined as typically a single fat droplet that expands the involved hepatocyte and is larger than adjacent nonsteatotic hepatocytes. Estimating severity of steatosis involves (i) low magnification estimate of the approximate surface area of the biopsy occupied by fat, (ii) higher magnification determination of the percentage of hepatocytes within the fatty area with LDF, and (iii) final score calculation. CONCLUSIONS: The proposed guidelines herein are intended to improve standardization in steatosis assessment of donor liver biopsies. The calculated percent LDF should be provided to the surgeon.

Collagen proportionate area correlates with histological stage and predicts clinical events in primary sclerosing cholangitis.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease in need of accurate biomarkers for stratification and as surrogates for clinical endpoints in trials. Quantitative liver fibrosis assessment by collagen proportionate area (CPA) measurement has been demonstrated to correlate with clinical outcomes in chronic hepatitis C, alcohol-related and non-alcoholic fatty liver disease. We aimed to investigate the ability of CPA to quantify liver fibrosis and predict clinical events in PSC. METHODS: Biopsies from 101 PSC patients from two European centres were retrospectively assessed by two expert pathologists in tandem, using grading (Ishak and Nakanuma) and staging (Ishak, Nakanuma, Ludwig) systems recently validated to predict clinical events in PSC. CPA was determined by image analysis of picro-Sirius red-stained sections following a standard protocol. We assessed the correlations between CPA, staging and grading and their associations with three outcomes: (1) time to PSC-related death, liver transplant or primary liver cancer; (2) liver transplant-free survival; (3) occurrence of cirrhosis-related clinical manifestations. RESULTS: CPA correlated strongly with histological stage determined by each scoring system (P < .001) and was significantly associated with the three endpoints. Median time to endpoint-1, endpoint-2 and endpoint-3 was shorter in patients with higher CPA, on Kaplan-Meier analyses (P = .011, P = .034 and P = .001, respectively). CONCLUSION: Quantitative fibrosis assessment by CPA has utility in PSC. It correlates with established histological staging systems and predicts clinical events. CPA may be a useful tool for staging fibrosis and for risk stratification in PSC and should be evaluated further within prospective clinical trials.

Combination antiretroviral therapy improves recurrent primary biliary cholangitis following liver transplantation.

Recurrent primary biliary cholangitis (rPBC) is frequent following liver transplantation and associated with increased morbidity and mortality. It has been argued that rPBC behaves like an infectious disease because more potent immunosuppression with tacrolimus is associated with earlier and more severe recurrence. Prophylactic ursodeoxycholic acid is an established therapeutic option to prevent rPBC, whereas the role of second line therapies, such as obeticholic acid and bezafibrate in rPBC, remains largely unexplored. To address the hypothesis that a human betaretrovirus plays a role in the development of PBC, we have tested antiretroviral therapy in vitro and conducted randomised controlled trials showing improvements in hepatic biochemistry. Herein, we describe the utility of combination antiretroviral therapy to manage rPBC in two patients treated with open label tenofovir/emtricitabine-based regimens in combination with either lopinavir or raltegravir. Both patients experienced sustained biochemical and histological improvement with treatment, but the antiretroviral therapy was associated with side effects.

Fifty years of impact on liver pathology: a history of the Gnomes.

Professional societies play a major role in medicine and science. The societies tend to be large with well-developed administrative structures. An additional model, however, is based on small groups of experts who meet regularly in an egalitarian model in order to discuss disease-specific scientific and medical problems. In order to illustrate the effectiveness of this model, the history and practices are examined of a long-standing successful example, the International Liver Pathology Group, better known as the Gnomes. The history shows that groups such as the Gnomes offer a number of important benefits not available in larger societies and nurturing such groups advances science and medicine in meaningful ways. The success of the Gnomes' approach provides a road map for future small scientific groups.

Alcoholic hepatitis and metabolic disturbance in female mice: a more tractable model than Nrf2-/- animals.

Alcoholic hepatitis (AH) is the dramatic acute presentation of alcoholic liver disease, with a 15% mortality rate within 28 days in severe cases. Research into AH has been hampered by the lack of effective and reproducible murine models that can be operated under different regulatory frameworks internationally. The liquid Lieber-deCarli (LdC) diet has been used as a means of ad libitum delivery of alcohol but without any additional insult, and is associated with relatively mild liver injury. The transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) protects against oxidative stress, and mice deficient in this molecule are suggested to be more sensitive to alcohol-induced injury. We have established a novel model of AH in mice and compared the nature of liver injury in C57/BL6 wild-type (WT) versus Nrf2-/- mice. Our data showed that both WT and Nrf2-/- mice demonstrate robust weight loss, and an increase in serum transaminase, steatosis and hepatic inflammation when exposed to diet and ethanol. This is accompanied by an increase in peripheral blood and hepatic myeloid cell populations, fibrogenic response and compensatory hepatocyte regeneration. We also noted characteristic disturbances in hepatic carbohydrate and lipid metabolism. Importantly, use of Nrf2-/- mice did not increase hepatic injury responses in our hands, and female WT mice exhibited a more-reproducible response. Thus, we have demonstrated that this simple murine model of AH can be used to induce an injury that recreates many of the key human features of AH - without the need for challenging surgical procedures to administer ethanol. This will be valuable for understanding of the pathogenesis of AH, for testing new therapeutic treatments or devising metabolic approaches to manage patients whilst in medical care.This article has an associated First Person interview with the joint first authors of the paper.

Transplantation of discarded livers following viability testing with normothermic machine perfusion.

There is a limited access to liver transplantation, however, many organs are discarded based on subjective assessment only. Here we report the VITTAL clinical trial (ClinicalTrials.gov number NCT02740608) outcomes, using normothermic machine perfusion (NMP) to objectively assess livers discarded by all UK centres meeting specific high-risk criteria. Thirty-one livers were enroled and assessed by viability criteria based on the lactate clearance to levels ≤2.5 mmol/L within 4 h. The viability was achieved by 22 (71%) organs, that were transplanted after a median preservation time of 18 h, with 100% 90-day survival. During the median follow up of 542 days, 4 (18%) patients developed biliary strictures requiring re-transplantation. This trial demonstrates that viability testing with NMP is feasible and in this study enabled successful transplantation of 71% of discarded livers, with 100% 90-day patient and graft survival; it does not seem to prevent non-anastomotic biliary strictures in livers donated after circulatory death with prolonged warm ischaemia.

Primary Sclerosing Cholangitis With Features of Autoimmune Hepatitis: Exploring the Global Variation in Management.

Patients with primary sclerosing cholangitis (PSC) frequently manifest features of autoimmune hepatitis (AIH). We sought to understand factors affecting expert management, with the goal of facilitating uniformity of care. A Survey Monkey questionnaire with four hypothetical cases suggesting a potential AIH/PSC variant was sent to hepatologists spanning global practices. Eighty responses from clinicians in 23 countries were obtained. Most of the respondents would request a liver biopsy, and stated that the cases presented could not be appropriately managed without a biopsy. Despite the fact that histology did not unequivocally support an AIH/PSC variant in three of the four cases, this diagnosis was reached by most of the respondents for all cases, except case 1, in which 49% were diagnosed with AIH/PSC. There was a wide variation of suggested medical treatment. For three cases, the most commonly chosen treatment options did not exceed 35%, indicating a lack management consensus. Most respondents would treat with ursodeoxycholic acid, despite current American Association for the Study of Liver Diseases guidelines, either alone or in combination with immunosuppression. European clinicians recommended ursodeoxycholic acid more frequently than their counterparts in North America (P < 0.05 in three out of four cases), who advocated the use of immunosuppression alone more commonly than Europeans (P = 0.005 in case 2). Conclusions: We document a wide variation in clinical decision making in the context of managing patients with a potential AIH/PSC variant. Guidance, likely based on systematic studies arising from prospective registries, is needed to better address this difficult clinician problem.

DSA Are Associated With More Graft Injury, More Fibrosis, and Upregulation of Rejection-associated Transcripts in Subclinical Rejection.

BACKGROUND: Subclinical T cell-mediated rejection (subTCMR) is commonly found after liver transplantation and has a good short-term prognosis, even when it is left untreated. Donor-specific antibodies (DSA) are putatively associated with a worse prognosis for recipient and graft after liver transplantation. METHODS: To assess the immune regulation in subTCMR grafts, gene expression of 93 transcripts for graft injury, tolerance, and immune regulation was analyzed in 77 biopsies with "no histologic rejection" (NHR; n = 25), "clinical TCMR" (cTMCR; n = 16), and subTCMR (n = 36). In addition, all available subTCMR biopsies (n = 71) were tested for DSA with bead assays. RESULTS: SubTCMR showed heterogeneous and intermediate expression profiles of transcripts that were upregulated in cTCMR. Graft gene expression suggested a lower activation of effector lymphocytes and a higher activation of regulatory T cells in grafts with subTCMR compared to cTCMR. DSA positivity in subTCMR was associated with histological evidence of more severe graft inflammation and fibrosis. This more severe DSA+ associated graft injury in subTCMR was converged with an upregulation of cTCMR-associated transcripts. In nonsupervised analysis, DSA positive subTCMR mostly clustered together with cTCMR, while DSA negative subTCMR clustered together with NHR. CONCLUSIONS: T cell-mediated rejection seems to form a continuum of alloimmune activation. Although subTCMR exhibited less expression of TCMR-associated transcript, DSA positivity in subTCMR was associated with an upregulation of rejection-associated transcripts. The identification of DSA positive subclinical rejection might help to define patients with more inflammation in the graft and development of fibrosis.

Hepatocytes Delete Regulatory T Cells by Enclysis, a CD4+ T Cell Engulfment Process.

CD4+ T cells play critical roles in directing immunity, both as T helper and as regulatory T (Treg) cells. Here, we demonstrate that hepatocytes can modulate T cell populations through engulfment of live CD4+ lymphocytes. We term this phenomenon enclysis to reflect the specific enclosure of CD4+ T cells in hepatocytes. Enclysis is selective for CD4+ but not CD8+ cells, independent of antigen-specific activation, and occurs in human hepatocytes in vitro, ex vivo, and in vivo. Intercellular adhesion molecule 1 (ICAM-1) facilitates T cell early adhesion and internalization, whereas hepatocytes form membrane lamellipodia or blebs to mediate engulfment. T cell internalization is unaffected by wortmannin and Rho kinase inhibition. Hepatocytes engulf Treg cells more efficiently than non-Treg cells, but Treg cell-containing vesicles preferentially acidify overnight. Thus, enclysis is a biological process with potential effects on immunomodulation and opens a new field for research to fully understand CD4+ T cell dynamics in liver inflammation.

Peribiliary gland damage due to liver transplantation involves peribiliary vascular plexus and vascular endothelial growth factor.

Extrahepatic bile ducts are characterized by the presence of peribiliary glands (PBGs), which represent stem cell niches implicated in biliary regeneration. Orthotopic liver transplantation may be complicated by non-anastomotic strictures (NAS) of the bile ducts, which have been associated with ischemic injury of PBGs and occur more frequently in livers obtained from donors after circulatory death than in those from brain-dead donors. The aims of the present study were to investigate the PBG phenotype in bile ducts after transplantation, the integrity of the peribiliary vascular plexus (PVP) around PBGs, and the expression of vascular endothelial growth factor-A (VEGF-A) by PBGs. Transplanted ducts obtained from patients who underwent liver transplantation were studied (N=62). Controls included explanted bile duct samples not used for transplantation (N=10) with normal histology. Samples were processed for histology, immunohistochemistry and immunofluorescence. Surface epithelium is severely injured in transplanted ducts; PBGs are diffusely damaged, particularly in ducts obtained from circulatory-dead compared to brain-dead donors. PVP is reduced in transplanted compared to controls. PBGs in transplanted ducts contain more numerous progenitor and proliferating cells compared to controls, show higher positivity for VEGF-A compared to controls, and express VEGF receptor-2. In conclusion, PBGs and associated PVP are damaged in transplanted extrahepatic bile ducts; however, an activation of the PBG niche takes place and is characterized by proliferation and VEGF-A expression. This response could have a relevant role in reconstituting biliary epithelium and vascular plexus and could be implicated in the genesis of non-anastomotic strictures.

Review article: unanswered clinical and research questions in autoimmune hepatitis-conclusions of the International Autoimmune Hepatitis Group Research Workshop.

BACKGROUND: Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease that results in substantial morbidity and mortality with many unanswered clinical and research questions. Improved understanding of disease pathogenesis, including the extra-hepatic manifestations of AIH, may allow targeted treatments with greater efficacy and fewer associated adverse events. AIM: To identify the spectrum of unanswered clinical and research questions facing care providers in the management of patients with autoimmune hepatitis (AIH). METHODS: The International Autoimmune Hepatitis Group initiated a series of research workshops to start to address these questions. Key issues were discussed in small group sessions with collation of all discussions to be summarised in this manuscript. RESULTS: Key issues were identified as: the need for better understanding of disease pathogenesis, standardisation of the methods and assays used to evaluate autoantibodies in AIH, refinement of the histopathological criteria for "typical" or "compatible" AIH, focus on the interaction with non-alcohol related fatty liver disease, how to treat acute severe AIH, better assessment of quality of life in adults and paediatrics, standardising use of standard, third-line and experimental therapies in AIH and search for biomarkers early in the disease course that predict outcome. CONCLUSION: This workshop has outlined the key unanswered clinical and research questions to help to define the research agenda in AIH.

Grand round: Autoimmune hepatitis.

Autoimmune hepatitis is a corticosteroid-responsive liver disease arising consequent to immunogenetic and environmental risk factors. The clinical course reflects relapsing and remitting, hepatocyte targeted immunologic damage, which is countered by reparative responses to cell injury. Appropriate and timely immunosuppressive therapy drives the disease into remission, albeit with inevitable side effects. Many challenges faced in the clinic reflect practice that must capture a heterogeneous disease presentation, course, and treatment response, as well as treatment tolerability. In this Grand Round we appraise the evidence supporting current treatment approaches, address the impact of autoimmune liver disease 'crossover or overlap' presentations, explore important clinical correlates to immune-serological classifiers, and discuss the factors influencing choice of alternative therapy in difficult-to-treat situations.