Developments in pediatric liver transplantation since implementation of the new allocation rules in Eurotransplant

Systematic Sex-Based Inequity in the MELD Score-Based Allocation System for Liver Transplantation in Germany

In liver allocation systems based on the Model for End-stage Liver Disease (MELD) score, sex inequities have been identified in countries with high organ donation rates. Whether similar inequities exist in regions with average to low donation rates remained unclear. We assessed the impact of sex on transplantation rates, waiting list mortality and post-transplant survival in 25,943 patients waitlisted for liver transplantation in Germany between 2003 and 2017 using competing risk analysis. Women are currently underrepresented on the waiting list (33.3%) and among transplant recipients (31.1%) compared to their proportion of severe liver disease cases (35.1%). The introduction of MELD-based allocation has worsened this disadvantage [HR before: 0.89 (0.81-0.98), after: 0.77 (0.74-0.81)]. Three key factors contribute to this disparity: Women have lower creatinine levels despite worse renal function, reducing their MELD score (median 1, 0-3). Second, exceptional MELD points are more frequently granted to men [HR 1.61 (1.54-1.69) compared to regular allocation]. Third, the small height of women has the highest impact on the probability of not being transplanted [adjusted HR 0.85 (0.81-0.9)]. Even in countries with lower organ donation rates, MELD-based allocation leads to sex inequity. Measures are needed to ensure sex-neutral liver allocation in MELD-based systems worldwide.

Improved survival of pediatric deceased donor liver transplantation recipients after introduction of the pediatric prioritization system: Analysis of data from a Japanese national survey

BACKGROUND

In Japan, there has never been a national analysis of pediatric deceased donor liver transplantation (pDDLT) based on donor and recipient factors. We constructed a Japanese nationwide database and assessed outcomes of pDDLT focusing on the pediatric prioritization system introduced in 2018.

METHODS

We collected data on pDDLTs (<18 years) performed between 1999 and 2021 from the Japan Organ Transplant Network and Japanese Liver Transplantation Society, identified risk factors for graft survival and compared the characteristics and graft survival in pDDLTs conducted before and after the introduction of the pediatric prioritization system.

RESULTS

Overall, 112 cases of pDDLT were included, with a 1-year graft survival rate of 86.6%. Four poor prognostic factors were identified: recipient intensive care unit stay, model for end-stage liver disease/pediatric end-stage liver disease score, donor cause of death, and donor total bilirubin. After the introduction of the system, allografts from pediatric donors were more reliably allocated to pediatric recipients and the annual number of pDDLTs increased. The 1-year graft survival rate improved significantly as did pDDLT conditions indicated by the risk factors.

CONCLUSIONS

Under the revised allocation system, opportunities for pDDLT increased, resulting in favorable recipient and donor conditions and improved survival.

Allocation to pediatric recipients around the world: An IPTA global survey of current pediatric solid organ transplantation deceased donation allocation practices

BACKGROUND

There has not been a comprehensive global survey of pediatric-deceased donor allocation practices across all organs since the advent of deceased donor transplantation at the end of the 20th century. As an international community that is responsible for transplanting children, we set out to survey the existing landscape of allocation. We aimed to summarize current practices and provide a snapshot overview of deceased donor allocation practices to children across the world.

METHODS

The International Registry in Organ Donation and Transplantation (IRODAT, www.irodat.org) was utilized to generate a list of all countries in the world, divided by continent, that performed transplantation. We reviewed the published literature, published allocation policy, individual website references and associated links to publicly available listed allocation policies. Following this, we utilized tools of communication, relationships, and international fellowship to confirm deceased donation pediatric centers and survey pediatric allocation practices for liver, kidney, heart, and lung across the world. We summarize pediatric allocation practices by organ when available using source documents, and personal communication when no source documents were available.

RESULTS

The majority of countries had either formal or informal policies directed toward minimizing organ distribution disparity among pediatric patients.

CONCLUSION

Children have long-term life to gain from organ donation yet continue to die while awaiting transplantation. We summarize global strategies that have been employed to provide meaningful and sustained benefit to children on the waitlist.

Pediatric transplantation: An international perspective

The international practice of transplant in the pediatric population is heterogenous. Global trends in pediatric transplant activity are increasing, with diffusion of transplant activities into developing and emerging economies. There have been impacts of the COVID-19 pandemic which have in the earlier part of the pandemic caused a decrease in the number of transplants. While deceased donor programs are well established in advanced economies, emerging and developing countries rely heavily on live donor programs. Prioritization of organs for children exists in different forms throughout the world. Pediatric transplantation as a sub-specialty is young but growing around the world with a need to train surgeons and physicians in this discipline. Outreach efforts with multi-national and multi-institutional partnerships have enabled resource poor countries to establish new transplant programs for children. Further international collaboration, good quality data collection and audit, prospective research and ongoing mentorship and education are needed to further improve outcomes of all children receiving solid organ transplants.

Whole liver transplantation in children under 10 kg: How to minimize the high risks of a still challenging procedure

BACKGROUND

Whole liver transplantation in infants <10 kg is a rare procedure with moderate outcomes (67%-79% graft survival at 1 year) and high rates of vascular complications (hepatic artery thrombosis 5-26%).

METHODS

Retrospective single-center analysis of whole liver transplantation in infants <10 kg and systematic review of the literature focused on survival rates and surgical complications.

RESULTS

Between January 2005 and December 2020, 175 liver transplantations in 173 children were performed at our center. A total of 92 (53%) children weighed less than 10 kg; 19 (21%) of them underwent WLT and constitute the study population. Median age of the recipients was 10 months (21 days-24 months) and median body weight 6.5 (3.1-9.8) kg. Median age of the donors was 5 (1-84) months and median body weight 6.1 (4-21) kg. Median donor-to-recipient body weight ratio was 1.2 (range: 0.6-4.5). Postoperatively, neither hepatic artery nor portal vein thrombosis occurred. A biliary complication occurred in 4 cases: 1 bile leak (early), 3 anastomotic stenoses (1 delayed and 2 late), and 1 non-anastomotic stenosis (late). Patient survival rate at 1, 5, and 10 years was 100%, 92%, and 92%, respectively. Overall, death-censored graft survival after 1, 5, and 10 was 100%.

CONCLUSION

Our results are excellent in terms of complications and graft and patient survival. This involves not only high-end surgical performance but also close interdisciplinary perioperative cooperation based on strong standard operating procedures and mainly focused on fluid management, hemostasiology, and strict monitoring of vessel patency.

Adult Liver Disease Prognostic Modelling for Long-term Outcomes in Biliary Atresia: An Observational Cohort Study

OBJECTIVES

To assess the utility of prognostic scoring systems for adolescents with biliary atresia (BA) surviving with native liver, for predicting the subsequent requirement for liver transplantation (LT).

METHODS

Single-centre retrospective analysis of 397 BA patients who received Kasai Portoenterostomy (KP) 1980-1996 and survived with the native liver at 16 years. Laboratory and clinical variables at 16 years (timepoint 16 years) were used to calculate (i) LT allocation scores; Model for End-Stage Liver Disease [MELD/MELD-sodium (Na)], and UK End-Stage Liver Disease (UKELD); (ii) Mayo Primary Sclerosing Cholangitis risk score (MayoPSC) and (iii) a modified Paediatric End-Stage Liver Disease (PELD) score. Scores were compared between patients requiring LT after 16 years of age (LT > 16 years), and those who survived with native liver, at the latest follow-up. Additional subgroup analysis for patients with data available at 12 years (timepoint 12 years).

RESULTS

MELD (area under the receiver operating characteristic [AUROC] 0.847) and UKELD (AUROC: 0.815) at 16 years of age predict the need for LT > 16 years. No advantage for MELD-Na over MELD was demonstrated. MELD >8.5 and UKELD >47 predicted LT > 16 years with 84% and 79% sensitivity and 73% and 73% specificity. PELD had a similar performance to MELD, but superiority to UKELD. MayoPSC revealed predictive accuracy for LT >16 years (AUROC 0.859), with a score of >0.87 predicting LT > 16 years with 85% sensitivity and 82% specificity. At timepoint 12 years, MELD and MayoPSC predicted LT >16 years. Change in MELD, PELD and MayoPSC between 12 and 16 years of age, was associated with LT >16 years.

CONCLUSIONS

Adult LT allocation scores may help monitor progress in adolescent BA, but the omission of relevant risk factors limits their utility for listing in this cohort. A BA-specific prognostic score would improve the management of adolescent BA.

Waiting list outcome of Peld/Meld exceptions: A single-center experience in Argentina

As PELD/MELD-based allocation policy was adopted in Argentina in 2005, a system of exception points has been in place in order to award increased waitlist priority to those patients whose severity of illness is not captured by the PELD/MELD score. We aimed to investigate the WL outcome of patients with granted PELD/MELD exceptions. A retrospective cohort study was conducted in children under 18 years old. WL outcomes were evaluated using univariable analysis. From 07/2005 to 01/2014, 408 children were listed for LT. There were 304 classified by calculated PELD/MELD. During this time, 85 (30%) PELD/MELD exceptions were granted. In this cohort, 89.4% (76 of 85) were transplanted and 7.1% (6 of 85) died while on the WL. The remaining 3 pts (3.5%) were removed from the WL due to other causes. We compared the impact of PELD/MELD exceptions in those 85 patients to outcomes in 87 non-exception patients with PELD/MELD ≥19 points. Patients with the exception had significantly better access to WL and lower WL mortality. Our data suggest that children listed by PELD/MELD exceptions had an advantage compared to children with CLD with equivalent PELD/MELD listing priorities.

Analysis of Liver Offers to Pediatric Candidates on the Transplant Wait List

BACKGROUND & AIMS

Approximately 10% of children on the liver transplant wait-list in the United States die every year. We examined deceased donor liver offer acceptance patterns and their contribution to pediatric wait-list mortality.

METHODS

We performed a retrospective cohort study of children on the US liver transplant wait-list from 2007 through 2014 using national transplant registry databases. We determined the frequency, patterns of acceptance, and donor and recipient characteristics associated with deceased donor liver organ offers for children who died or were delisted compared with those who underwent transplantation. Children who died or were delisted were classified by the number of donor liver offers (0 vs 1 or more), limiting analyses to offers of livers that were ultimately transplanted into pediatric recipients. The primary outcome was death or delisting on the wait-list.

RESULTS

Among 3852 pediatric liver transplant candidates, children who died or were delisted received a median 1 pediatric liver offer (inter-quartile range, 0-2) and waited a median 33 days before removal from the wait-list. Of 11,328 donor livers offered to children, 2533 (12%) were transplanted into children; 1179 of these (47%) were immediately accepted and 1354 (53%) were initially refused and eventually accepted for another child. Of 27,831 adults, 1667 (6.0%; median, 55 years) received livers from donors younger than 18 years (median, 15 years), most (97%) allocated locally or regionally. Of children who died or were delisted, 173 (55%) received an offer of 1 or more liver that was subsequently transplanted into another pediatric recipient, and 143 (45%) died or were delisted with no offers.

CONCLUSIONS

Among pediatric liver transplant candidates in the US, children who died or were delisted received a median 1 pediatric liver offer and waited a median of 33 days. Of livers transplanted into children, 47% were immediately accepted and 53% were initially refused and eventually accepted for another child. Of children who died or were delisted, 55% received an offer of 1 or more liver that was subsequently transplanted into another pediatric recipient, and 45% died or were delisted with no offers. Pediatric prioritization in the allocation and development of improved risk stratification systems is required to reduce wait-list mortality among children.

Impaired intention-to-treat survival after listing for liver transplantation in children with biliary atresia compared to other chronic liver diseases: 20 years' experience from the Nordic countries

Biliary atresia (BA) is the most common indication for LT in children. We investigated whether this diagnosis per se, compared to other chronic liver diseases (OCLD), had an influence on patient survival. Data from 421 Scandinavian children, 194 with BA and 227 with OCLD, listed for LT between 1990 and 2010 were analyzed. The intention-to-treat survival and influencing risk factors were studied. Patients with BA had higher risk of death after listing than patients with OCLD. The youngest (<1 year) and smallest (<10 kg) children with the highest bilirubin (>510 μmol/L), highest INR (>1.6), and highest PELD score (>20) listed during 1990s had the worst outcome. Given the same PELD score, patients with BA had higher risk of death than patients with OCLD. For adolescents, low weight/BMI was the only prognostic marker. Impaired intention-to-treat survival in patients with BA was mainly explained by more advanced liver disease in younger ages and higher proportion of young children in the BA group rather than diagnosis per se. PELD score predicted death, but seemed to underestimate the severity of liver disease in patients with BA. Poor nutritional status and severe cholestasis had negative impact on survival, supporting the "sickest children first" allocation policy and correction of malnutrition before surgery.

Global lessons in graft type and pediatric liver allocation: A path toward improving outcomes and eliminating wait-list mortality

Current literature and policy in pediatric liver allocation and organ procurement are reviewed here in narrative fashion, highlighting historical context, ethical framework, technical/procurement considerations, and support for a logical way forward to an equitable pediatric liver allocation system that will improve pediatric wait-list and posttransplant outcomes without adversely affecting adults. Where available, varying examples of successful international pediatric liver allocation and split-liver policy will be compared to current US policy to highlight potential strategies that can be considered globally. Liver Transplantation 23:86-95 2017 AASLD.

Heterogeneity and disparities in the use of exception scores in pediatric liver allocation

Physicians apply for Model for End-Stage Liver Disease/Pediatric End-Stage Liver Disease exception points on a case-by-case basis to improve an individual patient's chances of receiving a liver transplant. This retrospective cohort study describes trends in the use of exceptions among the pediatric liver waitlist population with chronic liver disease. The cohort (n = 3728) included all children with a diagnosis of chronic liver disease listed in the United Network for Organ Sharing transplant database for first isolated liver transplant between February 27, 2002 and March 31, 2013. Exception score requests were common (34%); 90% of requests were approved. The rate of exception score requests in 2013 was five times that of 2002 (incident rate ratios [IRR] 5.25, 95% confidence interval [CI] 3.19-8.63, p < 0.01). Patients of non-White race had exception score request rates 13% lower than patients of White race (IRR 0.87, 95% CI 0.77-0.98, p = 0.02). Older patients had lower rates of exception score requests than younger patients (p = 0.03). Request rates varied by region. Time spent at an active exception status nearly tripled the hazard rate for transplantation (hazard ratio = 2.90, 95% CI 2.62-3.21, p < 0.01). There is disparity in use of exceptions by race that is not explained by clinical disease severity, diagnosis, geography or other demographic factors.

Thrombin generation test in children and adolescents with chronic liver disease

INTRODUCTION

The aim of this study was to evaluate if real-time thrombin generation assay provides additional information to assess the hemostatic balance in children with liver disease as compared to routine coagulation tests.

PATIENTS AND METHODS

Sixty-three children with chronic liver disease were enrolled at our tertiary referral center for pediatric hepatology, eight whose routine coagulation tests gave abnormal results (Group A) and 55 whose test results were normal (Group B). Abnormal routine coagulation test was defined as at least one of the following: international normalized ratio≥1.4, activated partial thromboplastin time>44 sec., fibrinogen<1.5 g/L. Platelet-poor plasma was analyzed with the fluorogenic Calibrated Automated Thrombogram to test for thrombin generation, including endogenous thrombin potential. Further, routine coagulation tests and plasma levels of pro- and anticoagulant factors were measured. Twenty age-matched children without liver disease served as controls.

RESULTS

The endogenous thrombin potential in the 55 patients with normal routine coagulation tests was not significantly different from that in controls. Group A had significantly lower levels not only of procoagulant factors (II, V, VII, X) but simultaneously also of the anticoagulant factors antithrombin, protein S free, and protein C. These patients had a reduced endogenous thrombin potential compared to Group B, in agreement with their routine coagulation test results.

CONCLUSION

Thrombin generation analysis seems to give information on the hemostatic balance consistent with routine coagulation test results in children with liver disease. Further development and clinical evaluation of the method are warranted.