Obstacles to implement machine perfusion technology in routine clinical practice of transplantation: Why are we not there yet?

Machine perfusion of solid human organs is an old technique, and the basic principles were presented as early as 1855 by Claude Barnard. More than 50 years ago, the first perfusion system was used in clinical kidney transplantation. Despite the well-known benefits of dynamic organ preservation and significant medical and technical development in the last decades, perfusion devices are still not in routine use. This article describes the various challenges to implement this technology in practice, critically analyzing the role of all involved stakeholders, including clinicians, hospitals, regulatory, and industry, on the background of regional differences worldwide. The clinical need for this technology is discussed first, followed by the current status of research and the impact of costs and regulations. Considering the need for strong collaborations between clinical users, regulatory bodies, and industry, integrated road maps and pathways required to achieve a wider implementation are presented. The role of research development, clear regulatory pathways, and the need for more flexible reimbursement schemes is discussed together with potential solutions to address the most relevant hurdles. This article paints an overall picture of the current liver perfusion landscape and highlights the role of clinical, regulatory, and financial stakeholders worldwide.

Biliary complications after adult-to-adult living-donor liver transplantation: An international multicenter study of 3633 cases.

In living-donor liver transplantation, biliary complications including bile leaks and biliary anastomotic strictures remain significant challenges, with incidences varying across different centers. This multicentric retrospective study (2016-2020) included 3633 adult patients from 18 centers and aimed to identify risk factors for these biliary complications and their impact on patient survival. Incidences of bile leaks and biliary strictures were 11.4% and 20.6%, respectively. Key risk factors for bile leaks included multiple bile duct anastomoses (odds ratio, [OR] 1.8), Roux-en-Y hepaticojejunostomy (OR, 1.4), and a history of major abdominal surgery (OR, 1.4). For biliary anastomotic strictures, risk factors were ABO incompatibility (OR, 1.4), blood loss >1 L (OR, 1.4), and previous abdominal surgery (OR, 1.7). Patients experiencing biliary complications had extended hospital stays, increased incidence of major complications, and higher comprehensive complication index scores. The impact on graft survival became evident after accounting for immortal time bias using time-dependent covariate survival analysis. Bile leaks and biliary anastomotic strictures were associated with adjusted hazard ratios of 1.7 and 1.8 for graft survival, respectively. The study underscores the importance of minimizing these risks through careful donor selection and preoperative planning, as biliary complications significantly affect graft survival, despite the availability of effective treatments.

Long-term outcomes after hypothermic oxygenated machine perfusion and transplantation of 1,202 donor livers in a real-world setting (HOPE-REAL study).

BACKGROUND & AIM: We aimed to assess long-term outcome after transplantation of HOPE-treated donor livers based on real-world data (i.e., IDEAL-D stage 4). METHODS: In this international, multicentre, observational cohort study, we collected data from adult recipients of a HOPE-treated liver transplanted between January 2012 and December 2021. Analyses were stratified for brain-dead (DBD) and circulatory-dead (DCD) donor livers, sub-divided by their respective risk categories. The primary outcome was death-censored graft survival. Secondary outcomes included the incidence of primary non-function (PNF) and ischemic cholangiopathy (IC). RESULTS: We report on 1202 liver transplantations (64% DBD) performed at 22 European centres. For DBD, a total number of 99 benchmark (8%), 176 standard (15%), and 493 extended-criteria (41%) cases were included. For DCD, 117 transplants were classified as low-risk (10%), 186 as high-risk (16%), and 131 as futile (11%), with significant risk profile variations among centres. Actuarial 1-, 3-, and 5-year death-censored graft survival for DBD and DCD was 95%, 92%, and 91%, vs. 92%, 87%, and 81%, respectively (logrank p=0.003). Within DBD and DCD-strata, death-censored graft survival was similar among risk groups (logrank p=0.26, p=0.99). Graft loss due to PNF or IC was 2.3% and 0.4% (DBD), and 5% and 4.1% (DCD). CONCLUSIONS: This study shows excellent 5-year survival after transplantation of HOPE-treated DBD and DCD livers with low rates of graft loss due to PNF or IC, irrespective of their individual risk profile. HOPE-treatment has now reached IDEAL-D stage 4, which further supports the implementation of HOPE in routine clinical practice. IMPACT AND IMPLICATIONS: This study demonstrates the excellent long-term performance of HOPE-treatment of DCD and DBD liver grafts irrespective of their individual risk profile in a real-world setting, outside the evaluation of randomized controlled trials. While previous studies have established safety, feasibility, and efficacy against the current standard, according to the IDEAL-D evaluation framework, HOPE-treatment has now reached the final IDEAL-D Stage 4, which further supports the implementation of HOPE in routine clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05520320.

Age Matters: What Affects the Cumulative Lifespan of a Transplanted Liver?

OBJECTIVE: Assess factors affecting the cumulative lifespan of a transplanted liver. SUMMARY BACKGROUND DATA: Liver ageing is different from other solid organs. It is unknown how old a liver can actually get after liver transplantation (LT). METHODS: Deceased donor liver transplants from 1988-2021 were queried from the United States (US) UNOS registry. Cumulative liver age was calculated as donor age + recipient graft survival. RESULTS: In total, 184,515 livers were included. Most were DBD-donors (n=175,343). The percentage of livers achieving >70, 80, 90 and 100years cumulative age was 7.8% (n=14,392), 1.9% (n=3,576), 0.3% (n=528), and 0.01% (n=21), respectively. The youngest donor age contributing to a cumulative liver age >90years was 59years, with post-transplant survival of 34years. In pediatric recipients, 736 (4.4%) and 282 livers (1.7%) survived >50 and 60years overall, respectively. Transplanted livers achieved cumulative age >90years in 2.86-per-1000 and >100years in 0.1-per-1000. The US population at-large has a cumulative "liver age" >90years in 5.35-per-1000 persons, and >100y in 0.2-per-1000. Livers aged>60 years at transplant experienced both improved cumulative survival ( P <0.0001) and interestingly improved survival after transplantation ( P <0.0001). Recipient warm-ischemia-time of >30minutes was most predictive of reduced cumulative liver survival overall (n=184,515, HR=1.126, P <0.001) and excluding patients with mortality in the first 6month (n=151,884, HR=0.973, P <0.001). CONCLUSIONS: In summary, transplanted livers frequently get as old as those in the average population despite ischemic-reperfusion-injury and immunosuppression. The presented results justify using older donor livers regardless of donation type, even in sicker recipients with limited options.

Towards a Standardization of Learning Curve Assessment in Minimally Invasive Liver Surgery.

OBJECTIVE: The aim was to analyze the learning curves of minimal invasive liver surgery(MILS) and propose a standardized reporting. SUMMARY BACKGROUND DATA: MILS offers benefits compared to open resections. For a safe introduction along the learning curve, formal training is recommended. However, definitions of learning curves and methods to assess it lack standardization. METHODS: A systematic review of PubMed, Web of Science, and CENTRAL databases identified studies on learning curves in MILS. The primary outcome was the number needed to overcome the learning curve. Secondary outcomes included endpoints defining learning curves, and characterization of different learning phases(competency, proficiency and mastery). RESULTS: 60 articles with 12'241 patients and 102 learning curve analyses were included. The laparoscopic and robotic approach was evaluated in 71 and 18 analyses and both approaches combined in 13 analyses. Sixty-one analyses (60%) based the learning curve on statistical calculations. The most often used parameters to define learning curves were operative time (n=64), blood loss (n=54), conversion (n=42) and postoperative complications (n=38). Overall competency, proficiency and mastery were reached after 34 (IQR 19-56), 50 (IQR 24-74), 58 (IQR 24-100) procedures respectively. Intraoperative parameters improved earlier (operative time: competency to proficiency to mastery: -13%, 2%; blood loss: competency to proficiency to mastery: -33%, 0%; conversion rate (competency to proficiency to mastery; -21%, -29%), whereas postoperative complications improved later (competency to proficiency to mastery: -25%, -41%). CONCLUSIONS: This review summarizes the highest evidence on learning curves in MILS taking into account different definitions and confounding factors. A standardized three-phase reporting of learning phases (competency, proficiency, mastery) is proposed and should be followed.

How best to combine liver transplantation and bariatric surgery?-Results from a global, web-based survey.

BACKGROUND AND AIMS: Obesity is a growing healthcare challenge worldwide and a significant risk factor for liver failure as seen with non-alcoholic steatohepatitis (NASH). Combining metabolic-bariatric surgery (MBS) with liver transplantation (LT) appears as attractive strategy to treat both, the underlying liver disease and obesity. However, there is an ongoing debate on best timing and patient selection. This survey was designed to explore the current treatment practice for patients with NASH and obesity worldwide. METHODS: A web-based survey was conducted in 2022 among bariatric and LT surgeons, and hepatologists from Europe, North and South America and Asia. RESULTS: The survey completion rate was 74% (145/196). The average respondents were 41-50 years (38%), male (82.1%) and had >20 years of clinical experience (42.1%). Centres with a high LT-caseload for NASH were mainly located in the USA and United Kingdom. Almost 30% have already performed a combination of LT with MBS and 49% plan to do it. A majority of bariatric surgeons prefer MBS before LT (77.2%), whereas most of LT surgeons (52%) would perform MBS during LT. Most respondents (n = 114; 80%) favour sleeve gastrectomy over other bariatric techniques. One third (n = 42; 29.4%) has an established protocol regarding MBS for LT candidates. CONCLUSION: The most experienced centres doing LT for NASH are in the USA and United Kingdom with growing awareness worldwide. Overall, a combination of MBS and LT has already been performed by a third of respondents. Sleeve gastrectomy is the bariatric technique of choice-preferably performed either before or during LT.

Hepatic Artery Infusion Chemotherapy for Primary and Secondary Malignancies of the Liver: State of the Art and Current High-Level Evidence.

BACKGROUND: Hepatic artery infusion chemotherapy (HAI) has been proposed as a valuable adjunct for multimodal therapy of primary and secondary liver malignancies. This review provides an overview of the currently available evidence of HAI, taking into account tumor response and long-term oncologic outcome. SUMMARY: In colorectal liver metastases (CRLM), HAI in combination with systemic therapy leads to high response rates (85-90%) and conversion to resectablity in primary unresectable disease in up to 50%. HAI in combination with systemic therapy in CRLM in the adjuvant setting shows promising long-term outcomes with up to 50% 10-year survival in a large, non-randomized single-center cohort. For hepatocellular carcinoma patients, response rates as high as 20-40% have been reported for HAI and long-term outcomes compare well to other therapies. Similarly, survival for patients with unresectable intrahepatic cholangiocarcinoma 3 years after treatment with HAI is reported as high as 34%, which compares well to trials of systemic therapy where 3-year survival is usually below 5%. However, evidence is mainly limited by highly selected, heterogenous patient groups, and outdated chemotherapy regimens. The largest body of evidence stems from small, often non-randomized cohorts, predominantly from highly specialized single centers. KEY MESSAGE: In well-selected patients with primary and secondary liver malignancies, HAI might improve response rates and, possibly, long-term survival. Results of ongoing randomized trials will show whether a wider adoption of HAI is justified, particularly to increase rates of resectability in advanced malignant diseases confined to the liver.

Experts vs. machine - comparison of machine learning to expert-informed prediction of outcome after major liver surgery.

BACKGROUND: Machine learning (ML) has been successfully implemented for classification tasks (e.g., cancer diagnosis). ML performance for more challenging predictions is largely unexplored. This study's objective was to compare machine learning vs. expert-informed predictions for surgical outcome in patients undergoing major liver surgery. METHODS: Single tertiary center data on preoperative parameters and postoperative complications for elective hepatic surgery patients were included (2008-2021). Expert-informed prediction models were established on 14 parameters identified by two expert liver surgeons to impact on postoperative outcome. ML models used all available preoperative patient variables (n = 62). Model performance was compared for predicting 3-month postoperative overall morbidity. Temporal validation and additional analysis in major liver resection patients were conducted. RESULTS: 889 patients included. Expert-informed models showed low average bias (2-5 CCI points) with high over/underprediction. ML models performed similarly: average prediction 5-10 points higher than observed CCI values with high variability (95% CI -30 to 50). No performance improvement for major liver surgery patients. CONCLUSION: No clinical relevance in the application of ML for predicting postoperative overall morbidity was found. Despite being a novel hype, ML has the potential for application in clinical practice. However, at this stage it does not replace established approaches of prediction modelling.

Machine perfusion of the liver and bioengineering.

With the increasing number of accepted candidates on waiting lists worldwide, there is an urgent need to expand the number and the quality of donor livers. Dynamic preservation approaches have demonstrated various benefits, including improving liver function and graft survival, and reducing liver injury and post-transplant complications. Consequently, organ perfusion techniques are being used in clinical practice in many countries. Despite this success, a proportion of livers do not meet current viability tests required for transplantation, even with the use of modern perfusion techniques. Therefore, devices are needed to further optimise machine liver perfusion - one promising option is to prolong machine liver perfusion for several days, with ex situ treatment of perfused livers. For example, stem cells, senolytics, or molecules targeting mitochondria or downstream signalling can be administered during long-term liver perfusion to modulate repair mechanisms and regeneration. Besides, today's perfusion equipment is also designed to enable the use of various liver bioengineering techniques, to develop scaffolds or for their re-cellularisation. Cells or entire livers can also undergo gene modulation to modify animal livers for xenotransplantation, to directly treat injured organs or to repopulate such scaffolds with "repaired" autologous cells. This review first discusses current strategies to improve the quality of donor livers, and secondly reports on bioengineering techniques to design optimised organs during machine perfusion. Current practice, as well as the benefits and challenges associated with these different perfusion strategies are discussed.

Machine perfusion techniques for liver transplantation - A meta-analysis of the first seven randomized-controlled trials.

BACKGROUND & AIMS: Machine perfusion is increasingly being tested in clinical transplantation. Despite this, the number of large prospective clinical trials remains limited. The aim of this study was to compare the impact of machine perfusion vs. static cold storage (SCS) on outcomes after liver transplantation. METHODS: A systematic search of MEDLINE, EMBASE, CINAHL and the Cochrane Central Register of Controlled Trials (CENTRAL) was conducted to identify randomized-controlled trials (RCTs) comparing "post-transplant" outcomes following machine perfusion vs. SCS. Data were pooled using random effect models. Risk ratios (RRs) were calculated for relevant outcomes. The quality of evidence was rated using the GRADE-framework. RESULTS: Seven RCTs were identified (four on hypothermic oxygenated [HOPE] and three on normothermic machine perfusion [NMP]), including a total number of 1,017 patients. Both techniques were associated with significantly lower rates of early allograft dysfunction (NMP: n = 41/282, SCS: n = 74/253, RR 0.50, 95% CI 0.30-0.86, p = 0.01, I2 = 39%; HOPE: n = 45/241, SCS: n = 97/241, RR 0.48, 95% CI 0.35-0.65, p < 0.00001, I2 = 5%). The HOPE approach led to a significant reduction in major complications (Clavien Grade ≥IIIb; HOPE: n = 90/241; SCS: n = 117/241, RR 0.76, 95% CI 0.63-0.93, p = 0.006, I2 = 0%), "re-transplantation" (HOPE: n = 1/163; SCS: n = 11/163; RR 0.21, 95% CI 0.04-0.96, p = 0.04; I2 = 0%) and graft loss (HOPE: n = 7/163; SCS: n = 19/163; RR 0.40, 95% CI 0.17-0.95, p = 0.04; I2 = 0%). Both perfusion techniques were found to 'likely' reduce overall biliary complications and non-anastomotic strictures. CONCLUSIONS: Although this study provides the highest current evidence on the role of machine perfusion, outcomes remain limited to a 1-year follow-up after liver transplantation. Comparative RCTs and large real-world cohort studies with longer follow-up are required to enhance the robustness of the data further, thereby supporting the introduction of perfusion technologies into routine clinical practice. PROSPERO-REGISTRATION: CRD42022355252. IMPACT AND IMPLICATIONS: For a decade, two dynamic perfusion concepts have increasingly been tested in several transplant centres worldwide. We undertook the first systematic review and meta-analysis and identified seven published RCTs, including 1,017 patients, evaluating the effect of machine perfusion (hypothermic and normothermic perfusion techniques) compared to static cold storage in liver transplantation. Both perfusion techniques were associated with lower rates of early allograft dysfunction in the first week after liver transplantation. Hypothermic oxygenated perfusion led to a reduction in major complications, lower "re-transplantation" rates and better graft survival. Both perfusion strategies were found to 'likely' reduce overall biliary complications and non-anastomotic biliary strictures. This study provides the highest current evidence on the role of machine perfusion. Outcomes remain limited to a 1-year post-transplant follow-up. Larger cohort studies with longer follow-up and clinical trials comparing the perfusion techniques are required. This is especially relevant to provide clarity and optimise implementation processes further to support the commissioning of this technology worldwide.

Utilization of livers donated after circulatory death for transplantation - An international comparison.

BACKGROUND & AIMS: Liver graft utilization rates are a hot topic due to the worldwide organ shortage and the increasing number of transplant candidates on waiting lists. Liver perfusion techniques have been introduced in several countries, and may help to increase the organ supply, as they potentially enable the assessment of livers before use. METHODS: Liver offers were counted from donation after circulatory death (DCD) donors (Maastricht type III) arising during the past decade in eight countries, including Belgium, France, Italy, the Netherlands, Spain, Switzerland, the UK, and the US. Initial type-III DCD liver offers were correlated with accepted, recovered and implanted livers. RESULTS: A total number of 34,269 DCD livers were offered, resulting in 9,780 liver transplants (28.5%). The discard rates were highest in the UK and US, ranging between 70 and 80%. In contrast, much lower DCD liver discard rates, e.g. between 30-40%, were found in Belgium, France, Italy, Spain and Switzerland. In addition, we observed large differences in the use of various machine perfusion techniques, as well as in graft and donor risk factors. For example, the median donor age and functional donor warm ischemia time were highest in Italy, e.g. >40 min, followed by Switzerland, France, and the Netherlands. Importantly, such varying risk profiles of accepted DCD livers between countries did not translate into large differences in 5-year graft survival rates, which ranged between 60-82% in this analysis. CONCLUSIONS: Overall, DCD liver discard rates across the eight countries were high, although this primarily reflects the situation in the Netherlands, the UK and the US. Countries where in situ and ex situ machine perfusion strategies were used routinely had better DCD utilization rates without compromised outcomes. IMPACT AND IMPLICATIONS: A significant number of Maastricht type III DCD livers are discarded across Europe and North America today. The overall utilization rate among eight Western countries is 28.5% but varies significantly between 18.9% and 74.2%. For example, the median DCD-III liver utilization in five countries, e.g. Belgium, France, Italy, Switzerland, and Spain is 65%, in contrast to 24% in the Netherlands, UK and US. Despite this, and despite different rules and strategies for organ acceptance and preservation, 1- and 5-year graft survival rates remain fairly similar among all participating countries. A highly varying experience with modern machine perfusion technology was observed. In situ and ex situ liver perfusion concepts, and application of assessment tools for type-III DCD livers before transplantation, may be a key explanation for the observed differences in DCD-III utilization.

A multicenter randomized-controlled trial of hypothermic oxygenated perfusion (HOPE) for human liver grafts before transplantation.

BACKGROUND & AIMS: Machine perfusion is a novel method intended to optimize livers before transplantation. However, its effect on morbidity within a 1-year period after transplantation has remained unclear. METHODS: In this multicenter controlled trial, we randomly assigned livers donated after brain death (DBD) for liver transplantation (LT). Livers were either conventionally cold stored (control group), or cold stored and subsequently treated by 1-2 h hypothermic oxygenated perfusion (HOPE) before implantation (HOPE group). The primary endpoint was the occurrence of at least one post-transplant complication per patient, graded by the Clavien score of ≥III, within 1-year after LT. The comprehensive complication index (CCI), laboratory parameters, as well as duration of hospital and intensive care unit stay, graft survival, patient survival, and biliary complications served as secondary endpoints. RESULTS: Between April 2015 and August 2019, we randomized 177 livers, resulting in 170 liver transplantations (85 in the HOPE group and 85 in the control group). The number of patients with at least one Clavien ≥III complication was 46/85 (54.1%) in the control group and 44/85 (51.8%) in the HOPE group (odds ratio 0.91; 95% CI 0.50-1.66; p = 0.76). Secondary endpoints were also not significantly different between groups. A post hoc analysis revealed that liver-related Clavien ≥IIIb complications occurred less frequently in the HOPE group compared to the control group (risk ratio 0.26; 95% CI 0.07-0.77; p = 0.027). Likewise, graft failure due to liver-related complications did not occur in the HOPE group, but occurred in 7% (6 of 85) of the control group (log-rank test, p = 0.004, Gray test, p = 0.015). CONCLUSIONS: HOPE after cold storage of DBD livers resulted in similar proportions of patients with at least one Clavien ≥III complication compared to controls. Exploratory findings suggest that HOPE decreases the risk of severe liver graft-related events. IMPACT AND IMPLICATIONS: This randomized controlled phase III trial is the first to investigate the impact of hypothermic oxygenated perfusion (HOPE) on cumulative complications within a 12-month period after liver transplantation. Compared to conventional cold storage, HOPE did not have a significant effect on the number of patients with at least one Clavien ≥III complication. However, we believe that HOPE may have a beneficial effect on the quantity of complications per patient, based on its application leading to fewer severe liver graft-related complications, and to a lower risk of liver-related graft loss. The HOPE approach can be applied easily after organ transport during recipient hepatectomy. This appears fundamental for wide acceptance since concurring perfusion technologies need either perfusion at donor sites or continuous perfusion during organ transport, which are much costlier and more laborious. We conclude therefore that the post hoc findings of this trial should be further validated in future studies.

Defatting of Human Livers During Long-Term e x situ Normothermic Perfusion: Novel Strategy to Rescue Discarded Organs for Transplantation.

OBJECTIVE: To develop a protocol for the defatting of steatotic liver grafts during long-term ex situ normothermic machine perfusion. BACKGROUND: Despite the alarming increase in donor organ shortage, the highly prevalent fatty liver grafts are often discarded due to the risk of primary nonfunction. Effective strategies preventing such outcomes are currently lacking. An exciting new avenue is the introduction of ex situ normothermic machine perfusion (NMP), enabling a liver to remain fully functional for up to 2 weeks and providing a unique window of opportunity for defatting before transplantation. METHODS: Over a 5-year period, 23 discarded liver grafts and 28 partial livers from our resection program were tested during ex situ normothermic machine perfusion. The steatosis degree was determined on serial biopsies by expert pathologists, and triglyceride contents were measured simultaneously. RESULTS: Of 51 liver grafts, 20 were steatotic, with up to 85% macrovesicular steatosis, and were perfused for up to 12 days. Ten livers displayed marked (5 of which almost complete) loss of fat, while the other 10 did not respond to long-term perfusion. Successful defatting was related to prolonged perfusion, automated glucose control, circadian nutrition, and L-carnitine/fenofibrate supplementation. Pseudopeliotic steatosis and the associated activation of Kupffer/stellate cells were unexpected processes that might contribute to defatting. Synthetic and metabolic functions remained preserved for most grafts until perfusion ended. CONCLUSION: Ex situ long-term perfusion effectively reduces steatosis while preserving organ viability and may in the future allow transplantation of primarily unusable high-risk grafts, significantly increasing the number of organs available for transplantation.

Controversy Over Liver Transplantation or Resection for Neuroendocrine Liver Metastasis: Tumor Biology Cuts the Deal.

BACKGROUND: In patients with neuroendocrine liver metastasis (NELM), liver transplantation (LT) is an alternative to liver resection (LR), although the choice of therapy remains controversial. In this multicenter study, we aim to provide novel insight in this dispute. METHODS: Following a systematic literature search, 15 large international centers were contacted to provide comprehensive data on their patients after LR or LT for NELM. Survival analyses were performed with the Kaplan-Meier method, while multivariable Cox regression served to identify factors influencing survival after either transplantation or resection. Inverse probability weighting and propensity score matching was used for analyses with balanced and equalized baseline characteristics. RESULTS: Overall, 455 patients were analyzed, including 230 after LR and 225 after LT, with a median follow-up of 97 months [95% confidence interval (CI): 85-110 months]. Multivariable analysis revealed G3 grading as a negative prognostic factor for LR [hazard ratio (HR)=2.22, 95% CI: 1.04-4.77, P =0.040], while G2 grading (HR=2.52, 95% CI: 1.15-5.52, P =0.021) and LT outside Milan criteria (HR=2.40, 95% CI: 1.16-4.92, P =0.018) were negative prognostic factors in transplanted patients. Inverse probability-weighted multivariate analyses revealed a distinct survival benefit after LT. Matched patients presented a median overall survival (OS) of 197 months (95% CI: 143-not reached) and a 73% 5-year OS after LT, and 119 months (95% CI: 74-133 months) and a 52.8% 5-year OS after LR (HR=0.59, 95% CI: 0.3-0.9, P =0.022). However, the survival benefit after LT was lost if patients were transplanted outside Milan criteria. CONCLUSIONS: This multicentric study in patients with NELM demonstrates a survival benefit of LT over LR. This benefit depends on adherence to selection criteria, in particular low-grade tumor biology and Milan criteria, and must be balanced against potential risks of LT.

Novel Benchmark for Adult-to-Adult Living-donor Liver Transplantation: Integrating Eastern and Western Experiences.

OBJECTIVE: To define benchmark values for adult-to-adult living-donor liver transplantation (LDLT). BACKGROUND: LDLT utilizes living-donor hemiliver grafts to expand the donor pool and reduce waitlist mortality. Although references have been established for donor hepatectomy, no such information exists for recipients to enable conclusive quality and comparative assessments. METHODS: Patients undergoing LDLT were analyzed in 15 high-volume centers (≥10 cases/year) from 3 continents over 5 years (2016-2020), with a minimum follow-up of 1 year. Benchmark criteria included a Model for End-stage Liver Disease ≤20, no portal vein thrombosis, no previous major abdominal surgery, no renal replacement therapy, no acute liver failure, and no intensive care unit admission. Benchmark cutoffs were derived from the 75th percentile of all centers' medians. RESULTS: Of 3636 patients, 1864 (51%) qualified as benchmark cases. Benchmark cutoffs, including posttransplant dialysis (≤4%), primary nonfunction (≤0.9%), nonanastomotic strictures (≤0.2%), graft loss (≤7.7%), and redo-liver transplantation (LT) (≤3.6%), at 1-year were below the deceased donor LT benchmarks. Bile leak (≤12.4%), hepatic artery thrombosis (≤5.1%), and Comprehensive Complication Index (CCI ® ) (≤56) were above the deceased donor LT benchmarks, whereas mortality (≤9.1%) was comparable. The right hemiliver graft, compared with the left, was associated with a lower CCI ® score (34 vs 21, P < 0.001). Preservation of the middle hepatic vein with the right hemiliver graft had no impact neither on the recipient nor on the donor outcome. Asian centers outperformed other centers with CCI ® score (21 vs 47, P < 0.001), graft loss (3.0% vs 6.5%, P = 0.002), and redo-LT rates (1.0% vs 2.5%, P = 0.029). In contrast, non-benchmark low-volume centers displayed inferior outcomes, such as bile leak (15.2%), hepatic artery thrombosis (15.2%), or redo-LT (6.5%). CONCLUSIONS: Benchmark LDLT offers a valuable alternative to reduce waitlist mortality. Exchange of expertise, public awareness, and centralization policy are, however, mandatory to achieve benchmark outcomes worldwide.

Machine perfusion in liver transplantation.

Although liver transplantation is a true success story, many patients still die awaiting an organ. The increasing need for liver grafts therefore remains an unsolved challenge to the transplant community. To address this, transplant donor criteria have been expanded and, for example, more liver grafts with significant steatosis or from donors with circulatory death are being used. These marginal grafts, however, carry an increased risk of graft-associated complications, such as primary nonfunction, delayed graft function, or late biliary injuries. Therefore, reliable assessment of graft viability before use is essential for further success. To achieve this, machine liver perfusion, a procedure developed more than 50 years ago but almost forgotten at the end of the last century, is again of great interest. We describe in this review the clinical most applied machine perfusion techniques, their mechanistic background, and a novel concept of combining immediate organ assessment during hypothermic oxygenated perfusion, followed by an extended phase of normothermic machine perfusion, with simultaneous ex situ treatment of the perfused liver. Such a new approach may allow the pool of usable livers to dramatically increase and improve outcomes for recipients.

Donor-derived fulminant herpes simplex virus hepatitis after liver transplantation: Two cases and review of literature.

BACKGROUND: Fulminant herpetic hepatitis due to herpes simplex virus (HSV), serotype 1 or 2, is a rare but often fatal complication after solid organ transplantation (SOT). HSV hepatitis in SOT recipients can occur either due to primary infection acquired post transplantation, viral reactivation in a seropositive patient, or as donor-derived infection. Cases of fatal hepatitis have been reported in the liver as well as in other SOT recipients. The fatal outcome is mostly due to delayed diagnosis and treatment, which is explained by the lack of clinical specificity of HSV hepatitis. METHODS: We report two cases of fatal donor-derived HSV hepatitis in liver-transplanted recipients. We reviewed all published cases of donor-derived HSV infections after SOT with an evaluation of the presence of prophylaxis and outcome. RESULTS: In both liver recipients, the retrospective determination of HSV serostatus was negative, and both cases occurred in the absence of cytomegalovirus or HSV prophylaxis. A review of the literature showed a significant series of cases of severe hepatitis, mostly fatal, as well as the absence of specific preventive therapy guidelines in cases of HSV serology mismatch. CONCLUSIONS: The occurrence of two fatal donor-derived hepatitis made the Swiss Transplant Infectious Diseases working group modify its national recommendations regarding pretransplant serostatus determination and HSV prophylaxis after liver transplantation. Further studies are needed to assess this approach.

Observations and findings during the development of a subnormothermic/normothermic long-term ex vivo liver perfusion machine.

BACKGROUND: Ex situliver machine perfusion at subnormothermic/normothermic temperature isincreasingly applied in the field of transplantation to store and evaluateorgans on the machine prior transplantation. Currently, various perfusionconcepts are in clinical and preclinical applications. Over the last 6 years ina multidisciplinary team, a novel blood based perfusion technology wasdeveloped to keep a liver alive and metabolically active outside of the bodyfor at least one week. METHODS: Within thismanuscript, we present and compare three scenarios (Group 1, 2 and 3) we werefacing during our research and development (R&D) process, mainly linked tothe measurement of free hemoglobin and lactate in the blood based perfusate. Apartfrom their proven value in liver viability assessment (ex situ), these twoparameters are also helpful in R&D of a long-term liver perfusion machine and moreover supportive in the biomedical engineering process. RESULTS: Group 1 ("good" liver on the perfusion machine) represents the best liver clearance capacity for lactate and free hemoglobin wehave observed. In contrast to Group 2 ("poor" liver on the perfusion machine), that has shown the worst clearance capacity for free hemoglobin. Astonishingly,also for Group 2, lactate is cleared till the first day of perfusion andafterwards, rising lactate values are detected due to the poor quality of theliver. These two perfusate parametersclearly highlight the impact of the organ quality/viability on the perfusion process. Whereas Group 3 is a perfusion utilizing a blood loop only (without a liver). CONCLUSION: Knowing the feasible ranges (upper- and lower bound) and the courseover time of free hemoglobin and lactate is helpful to evaluate the quality ofthe organ perfusion itself and the maturity of the developed perfusion device. Freehemoglobin in the perfusate is linked to the rate of hemolysis that indicates how optimizing (gentle blood handling, minimizing hemolysis) the perfusion machine actually is. Generally, a reduced lactate clearancecapacity can be an indication for technical problems linked to the blood supplyof the liver and therefore helps to monitor the perfusion experiments.Moreover, the possibility is given to compare, evaluate and optimize developed liverperfusion systems based on the given ranges for these two parameters. Otherresearch groups can compare/quantify their perfusate (blood) parameters withthe ones in this manuscript. The presented data, findings and recommendations willfinally support other researchers in developing their own perfusion machine ormodifying commercially availableperfusion devices according to their needs.

Prolonged preservation by hypothermic machine perfusion facilitates logistics in liver transplantation: A European observational cohort study.

A short period (1-2 h) of hypothermic oxygenated machine perfusion (HOPE) after static cold storage is safe and reduces ischemia-reperfusion injury-related complications after liver transplantation. Machine perfusion time is occasionally prolonged for logistical reasons, but it is unknown if prolonged HOPE is safe and compromises outcomes. We conducted a multicenter, observational cohort study of patients transplanted with a liver preserved by prolonged (≥4 h) HOPE. Postoperative biochemistry, complications, and survival were evaluated. The cohort included 93 recipients from 12 European transplant centers between 2014-2021. The most common reason to prolong HOPE was the lack of an available operating room to start the transplant procedure. Grafts underwent HOPE for a median (range) of 4:42 h (4:00-8:35 h) with a total preservation time of 10:50 h (5:50-20:50 h). Postoperative peak ALT was 675 IU/L (interquartile range 419-1378 IU/L). The incidence of postoperative complications was low, and 1-year graft and patient survival were 94% and 88%, respectively. To conclude, good outcomes are achieved after transplantation of donor livers preserved with prolonged (median 4:42 h) HOPE, leading to a total preservation time of almost 21 h. These results suggest that simple, end-ischemic HOPE may be utilized for safe extension of the preservation time to ease transplantation logistics.

Protective mechanisms and current clinical evidence of hypothermic oxygenated machine perfusion (HOPE) in preventing post-transplant cholangiopathy.

The development of cholangiopathies after liver transplantation impacts on the quality and duration of graft and patient survival, contributing to higher costs as numerous interventions are required to treat strictures and infections at the biliary tree. Prolonged donor warm ischaemia time in combination with additional cold storage are key risk factors for the development of biliary strictures. Based on this, the clinical implementation of dynamic preservation strategies is a current hot topic in the field of donation after circulatory death (DCD) liver transplantation. Despite various retrospective studies reporting promising results, also regarding biliary complications, there are only a few randomised-controlled trials on machine perfusion. Recently, the group from Groningen has published the first randomised-controlled trial on hypothermic oxygenated perfusion (HOPE), demonstrating a significant reduction of symptomatic ischaemic cholangiopathies with the use of a short period of HOPE before DCD liver implantation. The most likely mechanism for this important effect, also shown in several experimental studies, is based on mitochondrial reprogramming under hypothermic aerobic conditions, e.g. exposure to oxygen in the cold, with a controlled and slow metabolism of ischaemically accumulated succinate and simultaneous ATP replenishment. This unique feature prevents mitochondrial oxidative injury and further downstream tissue inflammation. HOPE treatment therefore supports livers by protecting them from ischaemia-reperfusion injury (IRI), and thereby also prevents the development of post-transplant biliary injury. With reduced IRI-associated inflammation, recipients are also protected from activation of the innate immune system, with less acute rejections seen after HOPE.