Fatty liver allografts are associated with primary graft non-function and high mortality after transplantation

Graft inflow modulation in recipients with portal hypertension

The extended application of living donor liver transplantation (LDLT) has revealed the problem of graft size mismatching, potentially leading to the "small-for-size syndrome" (SFSS). SFSS is a rare dysfunction that may affect a partial liver graft, characterized by coagulopathy, cholestasis, ascites, and encephalopathy. A key role in the physiopathology of SFSS is played by portal hypertension (PHT) to which a small allograft is submitted after reperfusion, resulting in sinusoidal congestion and hemorrhage. Portal overflow injures the liver directly through nutrient excess, endothelial activation, and sinusoidal shear stress, and indirectly through arterial vasoconstriction. Thus, SFSS prevention relies not only on increasing graft volume (implementing the use of larger grafts or auxiliary/dual liver transplantation), but also on the control of the increased portal vein pressure (PVP) and portal vein flow (PVF). To this aim, surgical graft inflow modulation techniques (GIM) such as splenic artery ligation (SAL), splenectomy and hemiportocaval shunts, can be considered when an imbalance between the PVP and the hepatic arterial flow (HAF) is acknowledged. However, such strategies have their pros and cons, and a deep knowledge of the indications and complications is needed. Furthermore, pharmacological modulation has also been proposed. This review is aimed to update available literature on the current knowledge and strategies for modulating portal vein flow in LDLT.

Multinational Analysis of Marginal Liver Grafts Based on the Eurotransplant Extended Donor Criteria

OBJECTIVE

To evaluate the outcome of marginal liver grafts based on the Eurotransplant extended criteria donor (ECD) criteria.

BACKGROUND

Eurotransplant uses a broad definition of ECD criteria (age >65 years, steatosis >40%, body mass index >30 kg/m 2 , intensive care unit stay >7 days, donation after circulatory death, and certain laboratory parameters) for allocating organs to recipients who have consented to marginal grafts. Historically, marginal liver grafts were associated with increased rates of dysfunction.

METHODS

Retrospective cohort analysis using the German Transplant Registry and the U.S. Scientific Registry of Transplant Recipients (SRTR) from 2006 to 2016. Results were validated with recent SRTR data (2017-2022). Donors were classified according to the Eurotransplant ECD criteria, donation after circulatory death was excluded. Data were analyzed with cutoff prediction, binomial logistic regression, and multivariate Cox regression.

RESULTS

The study analyzed 92,330 deceased brain-dead donors (87% SRTR) and 70,374 transplants (87% SRTR) in adult recipients. Predominant ECD factors were donor age in Germany (30%) and body mass index in the United States (28%). Except for donor age, grafts meeting ECD criteria were not associated with impaired 1 or 3-year survival. Cutoffs had little to no predictive value for 30-day graft survival (area under the receiver operating curve: 0.49-0.52) and were nominally higher for age (72 vs 65 years) in Germany as compared with those defined by current Eurotransplant criteria.

CONCLUSIONS

The outcome of transplanted grafts from higher risk donors was nearly equal to standard donors with Eurotransplant criteria failing to predict survival of marginal grafts. Modifying ECD criteria could improve graft allocation and potentially expand the donor pool.

LiverColor: An Artificial Intelligence Platform for Liver Graft Assessment

Hepatic steatosis, characterized by excess fat in the liver, is the main reason for discarding livers intended for transplantation due to its association with increased postoperative complications. The current gold standard for evaluating hepatic steatosis is liver biopsy, which, despite its accuracy, is invasive, costly, slow, and not always feasible during liver procurement. Consequently, surgeons often rely on subjective visual assessments based on the liver's colour and texture, which are prone to errors and heavily depend on the surgeon's experience. The aim of this study was to develop and validate a simple, rapid, and accurate method for detecting steatosis in donor livers to improve the decision-making process during liver procurement. We developed LiverColor, a co-designed software platform that integrates image analysis and machine learning to classify a liver graft into valid or non-valid according to its steatosis level. We utilized an in-house dataset of 192 cases to develop and validate the classification models. Colour and texture features were extracted from liver photographs, and graft classification was performed using supervised machine learning techniques (random forests and support vector machine). The performance of the algorithm was compared against biopsy results and surgeons' classifications. Usability was also assessed in simulated and real clinical settings using the Mobile Health App Usability Questionnaire. The predictive models demonstrated an area under the receiver operating characteristic curve of 0.82, with an accuracy of 85%, significantly surpassing the accuracy of visual inspections by surgeons. Experienced surgeons rated the platform positively, appreciating not only the hepatic steatosis assessment but also the dashboarding functionalities for summarising and displaying procurement-related data. The results indicate that image analysis coupled with machine learning can effectively and safely identify valid livers during procurement. LiverColor has the potential to enhance the accuracy and efficiency of liver assessments, reducing the reliance on subjective visual inspections and improving transplantation outcomes.

Small-For-Size Syndrome and Graft Inflow Modulation Techniques in Liver Transplantation

BACKGROUND

Partial liver transplantation has recently been proposed to alleviate organ shortages. However, transplantation of a small-for-size graft is associated with an increased risk of posttransplant hepatic dysfunction, commonly referred to as small-for-size syndrome (SFSS). This review describes the etiology, pathological features, clinical manifestations, and diagnostic criteria of SFSS. Moreover, we summarize strategies to improve graft function, focusing on graft inflow modulation techniques. Finally, unmet needs and future perspectives are discussed.

SUMMARY

In fact, posttransplant SFSS can be attributed to various factors such as preoperative status of the recipients, surgical techniques, donor age, and graft quality, except for graft size. With targeted improvement measures, satisfactory clinical outcomes can be achieved in recipients at increased risk of SFSS. Given the critical role of relative portal hyperperfusion in the pathogenesis of SFSS, various pharmacological and surgical treatments have been established to reduce or partially divert excessive portal inflow, and recipients will benefit from individualized therapeutic regimens after careful evaluation of benefits against potential risks. However, there remain unmet needs for further research into different aspects of SFSS to better understand the correlation between portal hemodynamics and patient outcomes.

KEY MESSAGES

Contemporary transplant surgeons should consider various donor and recipient factors and develop case-specific prevention and treatment strategies to improve graft and recipient survival rates.

Health-related quality of life, uncertainty and coping strategies in solid organ transplant recipients during shielding for the COVID-19 pandemic

Strict isolation of vulnerable individuals has been a strategy implemented by authorities to protect people from COVID‐19. Our objective was to investigate health‐related quality of life (HRQoL), uncertainty and coping behaviours in solid organ transplant (SOT) recipients during the COVID‐19 pandemic. A cross‐sectional survey of adult SOT recipients undergoing follow‐up at our institution was performed. Perceived health status, uncertainty and coping strategies were assessed using the EQ‐5D‐5L, Short‐form Mishel Uncertainty in Illness Scale (SF‐MUIS) and Brief Cope, respectively. Interactions with COVID‐19 risk perception, access to health care, demographic and clinical variables were assessed. The survey was completed by 826 of 3839 (21.5%) invited participants. Overall, low levels of uncertainty in illness were reported, and acceptance was the major coping strategy (92%). Coping by acceptance, feeling protected, self‐perceived susceptibility to COVID‐19 were associated with lower levels of uncertainty. Health status index scores were significantly lower for those with mental health illness, compromised access to health care, a perceived high risk of severe COVID‐19 infection and higher levels of uncertainty. A history of mental health illness, risk perceptions, restricted healthcare access, uncertainty and coping strategies was associated with poorer HRQoL in SOT recipients during strict isolation. These findings may allow identification of strategies to improve HRQoL in SOT recipients during the pandemic.

Normothermic Ex Situ Liver Perfusion Enhances Mitochondrial Function of DCD Grafts as Evidenced by High-throughput Metabolomics

BACKGROUND

Normothermic ex situ liver perfusion (NEsLP) reduces reperfusion injury of donation after circulatory death (DCD) grafts and optimizes graft function. The goal of our study was to elucidate how NEsLP impacts global metabolism in DCD grafts using high-throughput metabolomics.

METHODS

Pig livers were preserved by 2 different techniques: static cold storage and NEsLP. Grafts obtained from heart-beating donors were compared with donation after circulatory death (DCD) grafts with either 30 minutes (DCD30) or 60 minutes (DCD60) ischemia time. Liver tissues were collected at the end of preservation period (T0) with either cold storage or NEsLP (n = 5 per group). Grafts were transplanted into recipient pigs and a second liver biopsy was collected 2 hours following liver transplantation (T1). Snap-frozen tissue was processed and analyzed by Sciex 6600 Q-TOF high-resolution mass spectrometer. Data analysis was performed using MetaboAnalyst 4.0 software.

RESULTS

Prolonged ischemia resulted in 38 out of 81 metabolites being differentially abundant over time. Mitochondrial metabolism was significantly affected, with disruption in oxidative phosphorylation capacity i.e the Warburg effect (P = 3.62E-03) and urea cycle (P = 7.95E-0.4). NEsLP resulted in improved mitochondrial metabolism and glycolysis (4.20E-02) oxidation of branched chain fatty acids (P = 4.07E-02).

CONCLUSIONS

This unbiased, high-throughput metabolomics study reveals that mitochondrial function is globally rescued with NEsLP, associated with improvement in DCD graft function. NEsLP is able to rescue DCD grafts, improving their metabolic function to that of livers not exposed to DCD procurement.

Noninvasive markers of liver steatosis and fibrosis after liver transplantation - Where do we stand?

In the last two decades, advances in immunosuppressive regimens have led to fewer complications of acute rejection crisis and consequently improved short-term graft and patient survival. In parallel with this great success, long-term post-transplantation complications have become a focus of interest of doctors engaged in transplant medicine. Metabolic syndrome (MetS) and its individual components, namely, obesity, dyslipidemia, diabetes, and hypertension, often develop in the post-transplant setting and are associated with immuno-suppressive therapy. Nonalcoholic fatty liver disease (NAFLD) is closely related to MetS and its individual components and is the liver manifestation of MetS. Therefore, it is not surprising that MetS and its individual components are associated with recurrent or "de novo" NAFLD after liver transplantation (LT). Fibrosis of the graft is one of the main determinants of overall morbidity and mortality in the post-LT period. In the assessment of post-LT steatosis and fibrosis, we have biochemical markers, imaging methods and liver biopsy. Because of the significant economic burden of post-LT steatosis and fibrosis and its potential consequences, there is an unmet need for noninvasive methods that are efficient and cost-effective. Biochemical scores can overestimate fibrosis and are not a good method for fibrosis evaluation in liver transplant recipients due to frequent post-LT thrombocytopenia. Transient elastography with controlled attenuation parameter is a promising noninvasive method for steatosis and fibrosis. In this review, we will specifically focus on the evaluation of steatosis and fibrosis in the post-LT setting in the context of de novo or recurrent NAFLD.

Assessment of Steatosis and Fibrosis in Liver Transplant Recipients Using Controlled Attenuation Parameter and Liver Stiffness Measurements

AIM

The primary objective of this study was to evaluate the prevalence of increased controlled attenuation parameter (CAP) and liver stiffness measurements (LSM) as surrogate markers of liver steatosis and fibrosis in liver transplant recipient (LTR). Secondary objectives were to determine the predictors of increased CAP and LSM in population of LTR.

METHODS

In this prospective, cross-sectional study, we have evaluated 175 LTRs' mean age as 61 (53-65) with a functioning graft for more than one year who came for regular outpatient examinations to the Department of Gastroenterology, University Hospital (UH) Merkur, Zagreb, Croatia.

RESULTS

Of 175 analyzed LTRs, 34.28% had obesity, 64.00% had hypertension, 38.28% had diabetes, and 58.85% had hyperlipidemia. The prevalence of liver steatosis was 68.57%, while the prevalence of severe liver steatosis was 46.85%. On multivariate analysis, independent factors associated with liver steatosis were male gender, total cholesterol as positive predictor, and HDL as negative predictor, and independent factors positively associated with severe liver steatosis were higher body mass index (BMI) and higher triglyceride levels. The prevalence of moderate liver fibrosis was 54.85%, while the prevalence of advanced liver fibrosis was 24%. On multivariate analysis, independent factors positively associated with moderate fibrosis were gamma-glutamyl transferase (GGT) and CAP, while the independent factor positively associated with advanced fibrosis was GGT.

CONCLUSION

Our study showed high prevalence of increased CAP and LSM measurements as surrogate markers of liver steatosis and fibrosis. Metabolic syndrome components were highly present and were associated with CAP and LSM values as well as in the pretransplant setting. Due to high prevalence of metabolic comorbidities and nonalcoholic fatty liver disease in LTRs and the lack of the abnormal liver test in a significant number of these patients, TE with CAP may be a reasonable initial assessment for LTRs with one or more components of the metabolic syndrome.

Nonalcoholic fatty liver disease and liver transplantation - Where do we stand?

Nonalcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH) is a challenging and multisystem disease that has a high socioeconomic impact. NAFLD/NASH is a main cause of macrovesicular steatosis and has multiple impacts on liver transplantation (LT), on patients on the waiting list for transplant, on post-transplant setting as well as on organ donors. Current data indicate new trends in the area of chronic liver disease. Due to the increased incidence of metabolic syndrome (MetS) and its components, NASH cirrhosis and hepatocellular carcinoma caused by NASH will soon become a major indication for LT. Furthermore, due to an increasing incidence of MetS and, consequently, NAFLD, there will be more steatotic donor livers and less high quality organs available for LT, in addition to a lack of available liver allografts. Patients who have NASH and are candidates for LT have multiple comorbidities and are unique LT candidates. Finally, we discuss long-term grafts and patient survival after LT, the recurrence of NASH and NASH appearing de novo after transplantation. In addition, we suggest topics and areas that require more research for improving the health care of this increasing patient population.