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Histopathology is a challenging interpretive discipline, and the level of confidence a pathologist has in their diagnosis is known to vary, which is conveyed descriptively in pathology reports. There has been little study to accurately quantify pathologists' diagnostic confidence or the factors that influence it. In this study involving sixteen pathologists from six NHS trusts, we assessed diagnostic confidence across multiple variables and four specialties. Each case was reported by four pathologists, with each pathologist reporting each case twice (on light microscopy (LM) and digital pathology (DP)). For each diagnosis, pathologists recorded their confidence on a 7-point Likert scale. This provided 16,187 diagnoses and associated confidence scores for analysis. All variables investigated were found to be significantly predictive of diagnostic confidence, except level of pathologist experience. Confidence was lower for difficult to report cases, cases where there was inter- and intra-pathologist variation in the diagnosis, and cases where the pathologist made an incorrect diagnosis. Confidence was higher, although nominally, for LM diagnoses than DP (rate ratio 1.09 (95% CI 1.01-1.18), p = 0.035), although results indicate pathologists are confident to report on DP. Lowest confidence scores were seen in areas of known diagnostic complexity and cases with quality issues. High confidence in incorrect diagnoses were almost invariably attributed to interpretive diagnostic differences which occurred across both rare and common lesions. The results highlight the value of external quality control schemes and the benefits of selective peer review when reporting., (© 2024. The Author(s).)

The Banff Heart Concurrent Session, held as part of the 16th Banff Foundation for Allograft Pathology Conference at Banff, Alberta, Canada, on September 21, 2022, focused on 2 major topics: non-human leukocyte antigen (HLA) antibodies and mixed rejection. Each topic was addressed in a multidisciplinary fashion with clinical, immunological, and pathology perspectives and future developments and prospectives. Following the Banff organization model and principles, the collective aim of the speakers on each topic was to • Determine current knowledge gaps in heart transplant pathology • Identify limitations of current pathology classification systems • Discuss next steps in addressing gaps and refining classification system., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Aims: To conduct a definitive multicentre comparison of digital pathology (DP) with light microscopy (LM) for reporting histopathology slides including breast and bowel cancer screening samples., Methods: A total of 2024 cases (608 breast, 607 GI, 609 skin, 200 renal) were studied, including 207 breast and 250 bowel cancer screening samples. Cases were examined by four pathologists (16 study pathologists across the four speciality groups), using both LM and DP, with the order randomly assigned and 6 weeks between viewings. Reports were compared for clinical management concordance (CMC), meaning identical diagnoses plus differences which do not affect patient management. Percentage CMCs were computed using logistic regression models with crossed random-effects terms for case and pathologist. The obtained percentage CMCs were referenced to 98.3% calculated from previous studies., Results: For all cases LM versus DP comparisons showed the CMC rates were 99.95% [95% confidence interval (CI) = 99.90-99.97] and 98.96 (95% CI = 98.42-99.32) for cancer screening samples. In speciality groups CMC for LM versus DP showed: breast 99.40% (99.06-99.62) overall and 96.27% (94.63-97.43) for cancer screening samples; [gastrointestinal (GI) = 99.96% (99.89-99.99)] overall and 99.93% (99.68-99.98) for bowel cancer screening samples; skin 99.99% (99.92-100.0); renal 99.99% (99.57-100.0). Analysis of clinically significant differences revealed discrepancies in areas where interobserver variability is known to be high, in reads performed with both modalities and without apparent trends to either., Conclusions: Comparing LM and DP CMC, overall rates exceed the reference 98.3%, providing compelling evidence that pathologists provide equivalent results for both routine and cancer screening samples irrespective of the modality used., (© 2024 The Authors. Histopathology published by John Wiley & Sons Ltd.)

The XVIth Banff Meeting for Allograft Pathology was held in Banff, Alberta, Canada, from September 19 to 23, 2022, as a joint meeting with the Canadian Society of Transplantation. In addition to a key focus on the impact of microvascular inflammation and biopsy-based transcript analysis on the Banff Classification, further sessions were devoted to other aspects of kidney transplant pathology, in particular T cell-mediated rejection, activity and chronicity indices, digital pathology, xenotransplantation, clinical trials, and surrogate endpoints. Although the output of these sessions has not led to any changes in the classification, the key role of Banff Working Groups in phrasing unanswered questions, and coordinating and disseminating results of investigations addressing these unanswered questions was emphasized. This paper summarizes the key Banff Meeting 2022 sessions not covered in the Banff Kidney Meeting 2022 Report paper and also provides an update on other Banff Working Group activities relevant to kidney allografts., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Normothermic machine perfusion (NMP) enables pretransplant assessment of high-risk donor livers. The VITTAL trial demonstrated that 71% of the currently discarded organs could be transplanted with 100% 90-day patient and graft survivals. Here, we report secondary end points and 5-year outcomes of this prospective, open-label, phase 2 adaptive single-arm study. The patient and graft survivals at 60 months were 82% and 72%, respectively. Four patients lost their graft due to nonanastomotic biliary strictures, one caused by hepatic artery thrombosis in a liver donated following brain death, and 3 in elderly livers donated after circulatory death (DCD), which all clinically manifested within 6 months after transplantation. There were no late graft losses for other reasons. All the 4 patients who died during the study follow-up had functioning grafts. Nonanastomotic biliary strictures developed in donated after circulatory death livers that failed to produce bile with pH >7.65 and bicarbonate levels >25 mmol/L. Histological assessment in these livers revealed high bile duct injury scores characterized by arterial medial necrosis. The quality of life at 6 months significantly improved in all but 4 patients suffering from nonanastomotic biliary strictures. This first report of long-term outcomes of high-risk livers assessed by normothermic machine perfusion demonstrated excellent 5-year survival without adverse effects in all organs functioning beyond 1 year (ClinicalTrials.gov number NCT02740608)., (Copyright © 2023 American Association for the Study of Liver Diseases.)

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., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Background: Unexplained acute failure of an initially functioning liver graft early post-transplant has been described as Seventh-Day Syndrome (7DS). The aims of this study were to describe the clinical syndrome in detail based on an institutional case series and literature review., Methods: A retrospective review of adult patients that underwent deceased donor liver transplantation at our institution between January 2010 and 2020 was performed to identify patients that developed 7DS. Relevant clinical variables were obtained from medical records. Existing cases in the literature were identified by a systematic literature search according to PRISMA guidelines. Pooled analysis was used to describe the incidence, retransplantation, and mortality rate. Histological findings from institutional and published literature cases were collected and appraised., Results: Six of 1,907 liver transplantations at our institution (0.3%) developed 7DS. Seven case series, describing 42 patients with 7DS, and two single case reports were identified from literature review. Pooled incidence of 7DS was low (2.1%, 95%CI: 0.7-3.9%) and associated with high mortality (74.8%, 95%CI: 49.2-94.6%). Retransplantation was performed in 23/42 (55%) patients and 4/23 (17%) survived. Review of histology showed frequent intrahepatic thrombi and arteritis. Rejection, with features of potential antibody mediated rejection, often preceded or accompanied progressive zonal coagulative necrosis and hemorrhage., Conclusions: 7DS is a rare clinical syndrome after liver transplantation and associated with high mortality. Antibody-mediated rejection, as suggested in early reports, is likely to be involved in the pathogenesis. Early recognition would allow rapid clinical diagnostics and expedited decisions, such as treatment of AMR if diagnosed or early retransplantation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Halle-Smith, Hall, Hann, Hartog, Perera and Neil.)

Normothermic machine perfusion (NMP) allows objective assessment of donor liver transplantability. Several viability evaluation protocols have been established, consisting of parameters such as perfusate lactate clearance, pH, transaminase levels, and the production and composition of bile. The aims of this study were to assess 3 such protocols, namely, those introduced by the teams from Birmingham (BP), Cambridge (CP), and Groningen (GP), using a cohort of high-risk marginal livers that had initially been deemed unsuitable for transplantation and to introduce the concept of the viability assessment sensitivity and specificity. To demonstrate and quantify the diagnostic accuracy of these protocols, we used a composite outcome of organ use and 24-month graft survival as a surrogate endpoint. The effects of assessment modifications, including the removal of the most stringent components of the protocols, were also assessed. Of the 31 organs, 22 were transplanted after a period of NMP, of which 18 achieved the outcome of 24-month graft survival. The BP yielded 94% sensitivity and 50% specificity when predicting this outcome. The GP and CP both seemed overly conservative, with 1 and 0 organs, respectively, meeting these protocols. Modification of the GP and CP to exclude their most stringent components increased this to 11 and 8 organs, respectively, and resulted in moderate sensitivity (56% and 44%) but high specificity (92% and 100%, respectively) with respect to the composite outcome. This study shows that the normothermic assessment protocols can be useful in identifying potentially viable organs but that the balance of risk of underuse and overuse varies by protocol., (© 2021 The Authors. Liver Transplantation published by Wiley Periodicals LLC on behalf of American Association for the Study of Liver Diseases.)

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., (© 2021 The Authors. Hepatology published by Wiley Periodicals LLC on behalf of American Association for the Study of Liver Diseases.)

Background: Retransplantation candidates are disadvantaged owing to lack of good-quality liver grafts. Strategies that can facilitate transplantation of suboptimal grafts into retransplant candidates require investigation. The aim was to determine whether late liver retransplantation can be performed safely with suboptimal grafts, following normothermic machine perfusion., Methods: A prospectively enrolled group of patients who required liver retransplantation received a suboptimal graft preserved via normothermic machine perfusion. This group was compared with both historical and contemporaneous cohorts of patient who received grafts preserved by cold storage. The primary outcome was 6-month graft and patient survival., Results: The normothermic machine perfusion group comprised 26 patients. The historical (cold storage 1) and contemporaneous (cold storage 2) groups comprised 31 and 25 patients respectively. The 6-month graft survival rate did not differ between groups (cold storage 1, 27 of 31, cold storage 2, 22 of 25; normothermic machine perfusion, 22 of 26; P = 0.934). This was despite the normothermic machine perfusion group having significantly more steatotic grafts (8 of 31, 7 of 25, and 14 of 26 respectively; P = 0.006) and grafts previously declined by at least one other transplant centre (5 of 31, 9 of 25, and 21 of 26; P < 0.001)., Conclusion: In liver retransplantation, normothermic machine perfusion can safely expand graft options without compromising short-term outcomes., (© The Author(s) 2022. Published by Oxford University Press on behalf of BJS Society Ltd. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Ex vivo normothermic machine liver perfusion (NMLP) involves artificial cannulation of vessels and generation of flow pressures. This could lead to shear stress-induced endothelial damage, predisposing to vascular complications, or improved preservation of donor artery quality. This study aims to assess the spatial donor hepatic artery (HA) endothelial quality downstream of the cannulation site after end-ischaemic NMLP., Methods: Remnant HA segments from the coeliac trunk up to the gastroduodenal artery branching were obtained after NMLP (n = 15) and after static cold storage (SCS) preservation (n = 15). Specimens were fixed in 10% neutral buffered formalin and sectioned at pre-determined anatomical sites downstream of the coeliac trunk. CD31 immunohistostaining was used to assess endothelial integrity by a 5-point ordinal scale (grade 0: intact endothelial lining, grade 5: complete denudation). Endothelial integrity after SCS was used as a control for the state of the endothelium at commencement of NMP., Results: In the SCS specimens, regardless of the anatomical site, near complete endothelial denudation was present throughout the HA (median scores 4.5-5). After NMLP, significantly less endothelial loss in the distal HA was present compared to SCS grafts (NMLP vs. SCS: median grade 3 vs. 4.5; p = 0.042). In NMLP specimens, near complete endothelial denudation was present at the cannulation site in all cases (median grade: 5), with significantly less loss of the endothelial lining the further from the cannulation site (proximal vs. distal, median grade 5 vs. 3; p = 0.005)., Conclusion: Loss of endothelial lining throughout the HA after SCS and at the cannulation site after NMLP suggests extensive damage related to surgical handling and preservation injury. Gradual improved endothelial lining along more distal sites of the HA after NMLP indicates potential for re-endothelialisation. The regenerative effect of NMLP on artery quality seems to occur to a greater extent further from the cannulation site. Therefore, arterial cannulation for machine perfusion of liver grafts should ideally be as proximal as possible on the coeliac trunk or aortic patch, while the site of anastomosis should preferentially be attempted distal on the common HA., (© 2021. Crown.)

Objectives: The aims of this study were to quantify preoperative myocardial fibrosis using late gadolinium enhancement (LGE), extracellular volume fraction (ECV%), and indexed extracellular volume (iECV) on cardiac magnetic resonance; determine whether this varies following surgery; and examine the impact on postoperative outcomes., Background: Myocardial fibrosis complicates chronic severe primary mitral regurgitation and is associated with left ventricular dilatation and dysfunction. It is not known if this nonischemic fibrosis is reversible following surgery or if it affects ventricular remodeling and patient outcomes., Methods: A multicenter prospective study was conducted among 104 subjects with primary mitral regurgitation undergoing mitral valve repair. Cardiac magnetic resonance and cardiopulmonary exercise stress testing were performed preoperatively and ≥6 months after surgery. Symptoms were assessed using the Minnesota Living With Heart Failure Questionnaire., Results: Mitral valve repair was performed for Class 2a indications in 65 patients and Class 1 indications in 39 patients. Ninety-three patients were followed up at 8.8 months (IQR: 7.4 months-10.6 months). Following surgery, there were significant reductions in both ECV% (from 27.4% to 26.6%; P = 0.027) and iECV (from 17.9 to 15.4 mL/m 2 ; P < 0.001), but the incidence of LGE was unchanged. Neither preoperative ECV% nor LGE affected postoperative function, but iECV predicted left ventricular end-systolic volume index (β = 1.04; 95% CI: 0.49 to 1.58; P < 0.001) and left ventricular ejection fraction (β = -0.61; 95% CI: -1.05 to -0.18; P = 0.006). Patients with above-median iECV of ≥17.6 mL/m 2 had significantly larger postoperative values of left ventricular end-systolic volume index (30.5 ± 12.7 mL/m 2 vs 23.9 ± 8.0 mL/m 2 ; P = 0.003), an association that remained significant in subcohort analyses of patients in New York Heart Association functional class I., Conclusions: Mitral valve surgery results in reductions in ECV% and iECV, which are surrogates of diffuse myocardial fibrosis, and preoperative iECV predicts the degree of postoperative remodeling irrespective of symptoms. (The Role of Myocardial Fibrosis in Degenerative Mitral Regurgitation; NCT02355418)., Competing Interests: Funding Support and Author Disclosures This research was fully funded by the British Heart Foundation (PG/14/74/31056). The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Competing Interests: Declaration of interests We declare no competing interests.

Background: Myocardial fibrosis occurs in end-stage heart failure secondary to mitral regurgitation (MR), but it is not known whether this is present before onset of symptoms or myocardial dysfunction. This study aimed to characterise myocardial fibrosis in chronic severe primary MR on histology, compare this to tissue characterisation on cardiovascular magnetic resonance (CMR) imaging, and investigate associations with symptoms, left ventricular (LV) function, and exercise capacity., Methods: Patients with class I or IIa indications for surgery underwent CMR and cardiopulmonary exercise testing. LV biopsies were taken at surgery and the extent of fibrosis was quantified on histology using collagen volume fraction (CVF mean ) compared to autopsy controls without cardiac pathology., Results: 120 consecutive patients (64 ± 13 years; 71% male) were recruited; 105 patients underwent MV repair while 15 chose conservative management. LV biopsies were obtained in 86 patients (234 biopsy samples in total). MR patients had more fibrosis compared to 8 autopsy controls (median: 14.6% [interquartile range 7.4-20.3] vs. 3.3% [2.6-6.1], P < 0.001); this difference persisted in the asymptomatic patients (CVF mean 13.6% [6.3-18.8], P < 0.001), but severity of fibrosis was not significantly higher in NYHA II-III symptomatic MR (CVF mean 15.7% [9.9-23.1] (P = 0.083). Fibrosis was patchy across biopsy sites (intraclass correlation 0.23, 95% CI 0.08-0.39, P = 0.001). No significant relationships were identified between CVF mean and CMR tissue characterisation [native T1, extracellular volume (ECV) or late gadolinium enhancement] or measures of LV function [LV ejection fraction (LVEF), global longitudinal strain (GLS)]. Although the range of ECV was small (27.3 ± 3.2%), ECV correlated with multiple measures of LV function (LVEF: Rho = - 0.22, P = 0.029, GLS: Rho = 0.29, P = 0.003), as well as NTproBNP (Rho = 0.54, P < 0.001) and exercise capacity (%PredVO 2 max: R = - 0.22, P = 0.030)., Conclusions: Patients with chronic primary MR have increased fibrosis before the onset of symptoms. Due to the patchy nature of fibrosis, CMR derived ECV may be a better marker of global myocardial status. Clinical trial registration Mitral FINDER study; Clinical Trials NCT02355418, Registered 4 February 2015, https://clinicaltrials.gov/ct2/show/NCT02355418.

The liver is an important contributor to the human immune system and it plays a pivotal role in the creation of both immunoreactive and tolerogenic conditions. Liver transplantation provides the best chance of survival for both children and adults with liver failure or cancer. With current demand exceeding the number of transplantable livers from donors following brain death, improved knowledge, technical advances and the desire to prevent avoidable deaths has led to the transplantation of organs from living, ABO incompatible (ABOi), cardiac death donors and machine based organ preservation with acceptable results. The liver graft is the most well-tolerated, from an immunological perspective, of all solid organ transplants. Evidence suggests successful cessation of immunosuppression is possible in ~20-40% of liver transplant recipients without immune mediated graft injury, a state known as "operational tolerance." An immunosuppression free future following liver transplantation is an ambitious but perhaps not unachievable goal. The initial immune response following transplantation is a sterile inflammatory process mediated by the innate system and the mechanisms relate to the preservation-reperfusion process. The severity of this injury is influenced by graft factors and can have significant consequences. There are minimal experimental studies that delineate the differences in the adaptive immune response to the various forms of liver allograft. Apart from ABOi transplants, antibody mediated hyperacute rejection is rare following liver transplant. T-cell mediated rejection is common following liver transplantation and its incidence does not differ between living or deceased donor grafts. Transplantation in the first year of life results in a higher rate of operational tolerance, possibly due to a bias toward Th2 cytokines (IL4, IL10) during this period. This review further describes the current understanding of the immunological response toward liver allografts and highlight the areas of this topic yet to be fully understood., (Copyright © 2020 Hann, Osei-Bordom, Neil, Ronca, Warner and Perera.)

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.

Changes within the Coronary veins secondary to pacing leads have not been described, this study assessed these changes in explanted hearts. Macroscopically fibrous sheaths formed around longstanding leads, leading to slit like channels for venous return in smaller veins. Histologically changes included bland fibrosis, a foreign body response to the lead, a chronic inflammatory response and inflammatory destruction of the media. Individuals responded in different ways with no clear relationship of changes to duration of the lead., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Supplemental oxygenation of the standard hypothermic machine perfusion (HMP) circuit has the potential to invoke favorable changes in metabolism, optimizing cadaveric organs before transplantation., Methods: Eight pairs of porcine kidneys underwent 18 hours of either oxygenated (HMP/O2) or aerated (HMP/Air) HMP in a paired donation after circulatory death model of transplantation. Circulating perfusion fluid was supplemented with the metabolic tracer universally labeled glucose.Perfusate, end-point renal cortex, and medulla samples underwent metabolomic analysis using 1-dimension and 2-dimension nuclear magnetic resonance experiments in addition to gas chromatography-mass spectrometry. Analysis of C-labeled metabolic products was combined with adenosine nucleotide levels and differences in tissue architecture., Results: Metabolomic analysis revealed significantly higher concentrations of universally labeled lactate in the cortex of HMP/Air versus HMP/O2 kidneys (0.056 mM vs 0.026 mM, P < 0.05). Conversely, newly synthesized [4,5-C] glutamate concentrations were higher in the cortex of HMP/O2 kidneys inferring relative increases in tricarboxylic acid cycle activity versus HMP/Air kidneys (0.013 mmol/L vs 0.003 mmol/L, P < 0.05). This was associated with greater amounts of adenoside triphosphate in the cortex HMP/O2 versus HMP/Air kidneys (19.8 mmol/mg protein vs 2.8 mmol/mg protein, P < 0.05). Improved flow dynamics and favorable ultrastructural features were also observed in HMP/O2 kidneys. There were no differences in thiobarbituric acid reactive substances and reduced glutathione levels, tissue markers of oxidative stress, between groups., Conclusions: The supplementation of perfusion fluid with high-concentration oxygen (95%) results in a greater degree of aerobic metabolism versus aeration (21%) in the nonphysiological environment of HMP, with reciprocal changes in adenoside triphosphate levels.

Hypothermic oxygenated perfusion (HOPE) and normothermic perfusion are seen as distinct techniques of ex situ machine perfusion of the liver. We aimed to demonstrate the feasibility of combining both techniques and whether it would improve functional parameters of donor livers into transplant standards. Ten discarded human donor livers had either 6 hours of normothermic perfusion (n = 5) or 2 hours of HOPE followed by 4 hours of normothermic perfusion (n = 5). Liver function was assessed according to our viability criteria; markers of tissue injury and hepatic metabolic activity were compared between groups. Donor characteristics were comparable. During the hypothermic perfusion phase, livers down-regulated mitochondrial respiration (oxygen uptake, P = 0.04; partial pressure of carbon dioxide perfusate, P = 0.04) and increased adenosine triphosphate levels 1.8-fold. Following normothermic perfusion, those organs achieved lower tissue expression of markers of oxidative injury (4-hydroxynonenal, P = 0.008; CD14 expression, P = 0.008) and inflammation (CD11b, P = 0.02; vascular cell adhesion molecule 1, P = 0.05) compared with livers that had normothermic perfusion alone. All livers in the combined group achieved viability criteria, whereas 40% (2/5) in the normothermic group failed (P = 0.22). In conclusion, this study suggests that a combined protocol of hypothermic oxygenated and normothermic perfusions might attenuate oxidative stress, tissue inflammation, and improve metabolic recovery of the highest-risk donor livers compared with normothermic perfusion alone., (Copyright © 2018 The Authors. Liver Transplantation published by Wiley Periodicals, Inc. on behalf of American Association for the Study of Liver Diseases.)

Increased use of high-risk allografts is critical to meet the demand for liver transplantation. We aimed to identify criteria predicting viability of organs, currently declined for clinical transplantation, using functional assessment during normothermic machine perfusion (NMP). Twelve discarded human livers were subjected to NMP following static cold storage. Livers were perfused with a packed red cell-based fluid at 37°C for 6 hours. Multilevel statistical models for repeated measures were employed to investigate the trend of perfusate blood gas profiles and vascular flow characteristics over time and the effect of lactate-clearing (LC) and non-lactate-clearing (non-LC) ability of the livers. The relationship of lactate clearance capability with bile production and histological and molecular findings were also examined. After 2 hours of perfusion, median lactate concentrations were 3.0 and 14.6 mmol/L in the LC and non-LC groups, respectively. LC livers produced more bile and maintained a stable perfusate pH and vascular flow >150 and 500 mL/minute through the hepatic artery and portal vein, respectively. Histology revealed discrepancies between subjectively discarded livers compared with objective findings. There were minimal morphological changes in the LC group, whereas non-LC livers often showed hepatocellular injury and reduced glycogen deposition. Adenosine triphosphate levels in the LC group increased compared with the non-LC livers. We propose composite viability criteria consisting of lactate clearance, pH maintenance, bile production, vascular flow patterns, and liver macroscopic appearance. These have been tested successfully in clinical transplantation. In conclusion, NMP allows an objective assessment of liver function that may reduce the risk and permit use of currently unused high-risk livers., (© 2018 by the American Association for the Study of Liver Diseases.)

LiverMultiScan is an emerging diagnostic tool using multiparametric MRI to quantify liver disease. In a two-centre prospective validation study, 161 consecutive adult patients who had clinically-indicated liver biopsies underwent contemporaneous non-contrast multiparametric MRI at 3.0 tesla (proton density fat fraction (PDFF), T1 and T2* mapping), transient elastography (TE) and Enhanced Liver Fibrosis (ELF) test. Non-invasive liver tests were correlated with gold standard histothological measures. Reproducibility of LiverMultiScan was investigated in 22 healthy volunteers. Iron-corrected T1 (cT1), TE, and ELF demonstrated a positive correlation with hepatic collagen proportionate area (all p < 0·001). TE was superior to ELF and cT1 for predicting fibrosis stage. cT1 maintained good predictive accuracy for diagnosing significant fibrosis in cases with indeterminate ELF, but not for cases with indeterminate TE values. PDFF had high predictive accuracy for individual steatosis grades, with AUROCs ranging from 0.90-0.94. T2* mapping diagnosed iron accumulation with AUROC of 0.79 (95% CI: 0.67-0.92) and negative predictive value of 96%. LiverMultiScan showed excellent test/re-test reliability (coefficients of variation ranging from 1.4% to 2.8% for cT1). Overall failure rates for LiverMultiScan, ELF and TE were 4.3%, 1.9% and 15%, respectively. LiverMultiScan is an emerging point-of-care diagnostic tool that is comparable with the established non-invasive tests for assessment of liver fibrosis, whilst at the same time offering a superior technical success rate and contemporaneous measurement of liver steatosis and iron accumulation.

Discussion of liver antibody-mediated rejection during the 2011, 2013, and 2015 Banff liver sessions raised concerns over reliability of complement fragment 4d (C4d) staining, precipitating a global survey followed by a tissue microarray staining quality assessment study among centers on formalin-fixed, paraffin-embedded tissue. Tissue microarray sections containing tissue plugs of resected native and allograft (with acute antibody-mediated rejection) liver, heart, and kidney (n = 33 total cores) were sent to 31 centers for C4d staining using local method(s) and pathologist scoring. Digital whole-slide images (n = 40) were then semiquantitatively scored by 7 experts for background, distribution, and intensity of portal vein and capillary, hepatic artery, sinusoidal, and central vein endothelia and portal and central stromal staining. Results showed that strong and diffuse portal vein and capillary C4d staining, as determined by both local and central pathologists, clearly distinguished allografts showing acute antibody-mediated rejection from native livers and from those with evidence of weaker donor-specific antibody. Downstream vascular endothelial cell C4d staining and assessment were more variable and difficult to identify. C4d staining in the majority of laboratories reliably detects acute liver allograft antibody-mediated rejection in formalin-fixed, paraffin-embedded tissues. Assessment should focus on portal veins and capillaries, sinusoids, and central veins present in peripheral core needle biopsies. C4d staining in one organ does not always translate to staining in another., (Copyright © 2018. Published by Elsevier Inc.)

Current cold storage organ preservation technique fails to preserve marginal donor grafts sufficiently. Evidence from large animal experiments suggests superiority of normothermic machine preservation of liver allografts. Long-term organ preservation using normothermic perfusion might not only allow organ viability assessment before transplantation, but also provide the means for further organ modifications under physiologic conditions. Previous research has shown that porcine livers can be transplanted successfully after normothermic preservation of 20 hours. In the present study we investigate whether similar methodology is capable of further extending the safe limit to 48 hours. In this study, livers from White Landrace pigs were preserved by normothermic, oxygenated sanguineous perfusion. After a 48-hour period of preservation, livers were transplanted into recipient pigs and followed for 5 days. Outcome parameters measured included markers of synthetic and metabolic liver function as well as hepatocellular injury and blood gas analysis during perfusion and follow-up. Histological assessment of morphological liver integrity was performed. All livers showed sustained bile production and metabolic activity throughout the preservation period. Low levels of hepatocellular damage were found. Following transplantation all liver grafts revealed excellent graft function and death-censored graft survival was 100%. Porcine livers were transplanted successfully following 48 hours normothermic machine preservation.

Background: Normothermic machine perfusion of the liver (NMP-L) is a novel technique that preserves liver grafts under near-physiological conditions while maintaining their normal metabolic activity. This process requires an adequate oxygen supply, typically delivered by packed red blood cells (RBC). We present the first experience using an acellular hemoglobin-based oxygen carrier (HBOC) Hemopure in a human model of NMP-L., Methods: Five discarded high-risk human livers were perfused with HBOC-based perfusion fluid and matched to 5 RBC-perfused livers. Perfusion parameters, oxygen extraction, metabolic activity, and histological features were compared during 6 hours of NMP-L. The cytotoxicity of Hemopure was also tested on human hepatic primary cell line cultures using an in vitro model of ischemia reperfusion injury., Results: The vascular flow parameters and the perfusate lactate clearance were similar in both groups. The HBOC-perfused livers extracted more oxygen than those perfused with RBCs (O2 extraction ratio 13.75 vs 9.43 % ×10 per gram of tissue, P = 0.001). In vitro exposure to Hemopure did not alter intracellular levels of reactive oxygen species, and there was no increase in apoptosis or necrosis observed in any of the tested cell lines. Histological findings were comparable between groups. There was no evidence of histological damage caused by Hemopure., Conclusions: Hemopure can be used as an alternative oxygen carrier to packed red cells in NMP-L perfusion fluid.