Safe use of highly steatotic livers by utilizing a donor/recipient clinical algorithm

Deep Learning-Based Survival Analysis for Receiving a Steatotic Donor Liver Versus Waiting for a Standard Liver

BACKGROUND

An emerging strategy to expand the donor pool is the use of a steatotic donor liver (SDLs; ≥ 30% macrosteatosis on biopsy). With the obesity epidemic and prevalence of nonalcoholic fatty liver disease, SDLs have been reported in 59% of all deceased donors. Many potential candidates need to decide whether to accept an SDL offer or remain on the waitlist for a nonsteatotic donor liver (non-SDL). The objective of this study was to compare the survival of accepting an SDL vs using a non-SDL after waiting various times.

METHODS

Using data from the United States' organ procurement and transplantation network, deep survival learning predictive models were built to compare post-decision survival after accepting an SDL vs waiting for a non-SDL. The comparison subjects contain simulated 20,000 different scenarios of a candidate either accepting an SDL immediately or receiving a non-SDL after waiting various times. The research variables were selected using the LASSO-Cox and Random Survival Forest (RSF) models. The Cox proportional hazards and RSF models were also comparatively included for survival prediction. In addition, personalized survival curves for randomly selected candidates were generated.

RESULT

Deep survival learning outperformed Cox proportional hazards and RSF in predicting the survival of liver transplants. Among the simulations, 25% to 30% of scenarios demonstrated a higher 3-year survival post-decision for candidates accepting an SDL than waiting and receiving a non-SDL. The difference was only 1.43% in 3-year survival post-decision between accepting an SDL and waiting 260 days (mean waitlist time) for a non-SDL. As the number of days on the waitlist increases, the difference in survival between accepting SDLs and waiting for non-SDLs decreases.

CONCLUSIONS

Appropriately used SDLs could expand the donor pool and relieve the candidates' unmet need for donor livers, which presents long-term survival benefits for recipients.

Evaluating Outcomes Related to Donor and Recipient Metabolic Environment: Macrosteatotic Allografts and Nonalcoholic Steatohepatitis

The increasing prevalence of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) affects both recipient and donor populations in liver transplantation. Presently, it is unclear whether transplantation of macrosteatotic allografts is affected by the metabolic milieu of liver transplant recipients. This study investigates fatty liver disease at the intersection of donor and recipient. A retrospective review of the Organ Procurement and Transplantation database identified 5167 NASH and 26,289 non-NASH transplant recipients who received transplants from January 1, 2004, to June 12, 2020. A total of 12,569 donors had allografts with no macrosteatosis (<5%), 16,140 had mild macrosteatosis (5%-29%), and 2747 had moderate to severe macrosteatosis (≥30%). Comparing recipients with NASH to propensity score-matched (PSM) recipients without NASH demonstrated noninferior graft and patient survival up to 10 years in patients with NASH. Similar trends were observed in subgroup analyses of transplants within each strata of allograft macrosteatosis. Assessing allograft macrosteatosis specifically in the NASH population demonstrated that allografts with ≥30% macrosteatosis were associated with reduced early graft survival (30 days, 93.32% versus 96.54% [P = 0.02]; 1 year, 84.53% versus 88.99% [P = 0.05]) compared with PSM grafts with <30% macrosteatosis. Long-term graft survival at 5 and 10 years, however, was similar. The use of carefully selected macrosteatotic allografts can be successful in both recipients with NASH and recipients without NASH. The metabolic environment of patients with NASH does not appear to adversely affect outcomes with regard to the allograft when controlled for numerous confounders. It is, however, important to remain cognizant of the potential for high-risk macrosteatotic allografts to negatively affect outcomes.

A Clinical Tool to Guide Selection and Utilization of Marginal Donor Livers With Graft Steatosis in Liver Transplantation

Supplemental Digital Content is available in the text.

Background.

Donor liver biopsy (DLBx) in liver transplantation provides information on allograft quality; however, predicting outcomes from these allografts remains difficult.

Methods.

Between 2006 and 2015, 16 691 transplants with DLBx were identified from the Standard Transplant Analysis and Research database. Cox proportional hazard regression analyses identified donor and recipient characteristics associated with 30-d, 90-d, 1-y, and 3-y graft survival. A composite model, the Liver Transplant After Biopsy (LTAB) score, was created. The Mini-LTAB was then derived consisting of only donor age, macrosteatosis on DLBx, recipient model for end-stage liver disease score, and cold ischemic time. Risk groups were identified for each score and graft survival was evaluated. P values <0.05 were considered significant.

Results.

The LTAB model used 14 variables and 5 risk groups and identified low-, mild-, moderate-, high-, and severe-risk groups. Compared with moderate-risk recipients, severe-risk recipients had increased risk of graft loss at 30 d (hazard ratio, 3.270; 95% confidence interval, 2.568-4.120) and at 1 y (2.258; 1.928-2.544). The Mini-LTAB model identified low-, moderate-, and high-risk groups. Graft survival in Mini-LTAB high-risk transplants was significantly lower than moderate- or low-risk transplants at all time points.

Conclusions.

The LTAB and Mini-LTAB scores represent guiding principles and provide clinically useful tools for the successful selection and utilization of marginal allografts in liver transplantation.

Contemporary strategies to assess and manage liver donor steatosis: a review

PURPOSE OF REVIEW

Due to a persistent shortage of donor livers, attention has turned toward ways of utilizing marginal grafts, particularly those with steatosis, without incurring inferior outcomes. Here we review the evaluation and utilization of steatotic liver allografts, highlight recently published data, and discuss novel methods of graft rehabilitation.

RECENT FINDINGS

Although severe liver allograft (>60%) steatosis has been associated with inferior graft and recipient outcomes, mild (<30%) steatosis has not. There is ongoing debate regarding safe utilization of grafts with moderate (30-60%) steatosis. Presently, no established protocols for evaluating steatosis in donor candidates or utilizing such grafts exist. Liver biopsy is accepted as the gold standard technique, though noninvasive methods have shown promise in accurately predicting steatosis. More recently, machine perfusion has been shown to enhance ex situ liver function and reduce steatosis, emerging as a potential means of optimizing steatotic grafts prior to transplantation.

SUMMARY

Steatotic liver allografts constitute a large proportion of deceased donor organs. Further work is necessary to define safe upper limits for the acceptable degree of steatosis, develop standardized evaluation protocols, and establish utilization guidelines that prioritize safety. Machine perfusion has shown promise in rehabilitating steatotic grafts and offers the possibility of expanding the deceased donor pool.

Efficiency of Machine Learning Algorithms for the Determination of Macrovesicular Steatosis in Frozen Sections Stained with Sudan to Evaluate the Quality of the Graft in Liver Transplantation

Liver transplantation is the only curative treatment option in patients diagnosed with end-stage liver disease. The low availability of organs demands an accurate selection procedure based on histological analysis, in order to evaluate the allograft. This assessment, traditionally carried out by a pathologist, is not exempt from subjectivity. In this sense, new tools based on machine learning and artificial vision are continuously being developed for the analysis of medical images of different typologies. Accordingly, in this work, we develop a computer vision-based application for the fast and automatic objective quantification of macrovesicular steatosis in histopathological liver section slides stained with Sudan stain. For this purpose, digital microscopy images were used to obtain thousands of feature vectors based on the RGB and CIE L*a*b* pixel values. These vectors, under a supervised process, were labelled as fat vacuole or non-fat vacuole, and a set of classifiers based on different algorithms were trained, accordingly. The results obtained showed an overall high accuracy for all classifiers (>0.99) with a sensitivity between 0.844 and 1, together with a specificity >0.99. In relation to their speed when classifying images, KNN and Naïve Bayes were substantially faster than other classification algorithms. Sudan stain is a convenient technique for evaluating ME in pre-transplant liver biopsies, providing reliable contrast and facilitating fast and accurate quantification through the machine learning algorithms tested.

Higher thresholds for the utilization of steatotic allografts in liver transplantation: Analysis from a U.S. national database

Background

Historically, liver allografts with >30% macrosteatosis (MaS) on donor biopsy have been associated with early allograft dysfunction and worse graft survival; however, successful outcomes have been reported in small cohorts. This study proposes an elevated MaS threshold for organ utilization without detriment to graft survival.

Methods

The UNOS Standard Transplant Analysis and Research database was evaluated for transplants between 2006–2015. Graft survival up to 1-year was evaluated by Kaplan-Meier (KM) survival analyses, and by univariate and multivariable logistic regression analyses, including donor and recipient characteristics. Odds ratios (OR) with 95% confidence intervals (CI) for risk of graft loss are reported.

Results

Thirty-day risk of graft loss was increased with MaS as low as 10–19% (OR [95% CI] 1.301 [1.055–1.605], p<0.0001) and peaked with MaS 50–59% (2.921 [1.672–5.103]). At 1-year, risk of graft loss remained elevated with MaS 40–49% (1.465 [1.002–2.142]) and MaS 50–59% (1.978 [1.281–3.056], p = 0.0224). Multivariable models were created for Lower and Higher MELD recipients and MaS cutoffs were established. In Lower MELD recipients, organs with ≥50% MaS had increased risk of graft loss at 30 days (2.451 [1.541–3.897], p = 0.0008) and 1-year post-transplant (1.720 [1.224–2.418], p = 0.0125). Higher MELD recipients had increased risk of graft loss at 30 days with allografts showing MaS ≥40% (4.204 [1.440–5.076], p = 0.0016). At 1-year the risk remained increased, but MaS was not significant predictor of graft loss.048 [1.131–3.710], p = 0.0616). In both MELD cohorts, organs with MaS levels below threshold had similar survival to those transplanted without a donor biopsy.

Conclusions

In conjunction with recipient selection, organs with MaS up to 50% may be safely used without detriment to outcomes.

The role of deceased donor liver biopsy: An analysis of 5449 liver transplant recipients

BACKGROUND

No standard exists for the use of deceased donor liver biopsy during procurement. We sought to evaluate liver biopsy and the impact of findings on outcomes and graft utilization.

METHODS

A prospective observational study of donors after neurologic determination of death was conducted from 02/2012-08/2017 (16 OPOs). Donor data were collected through the UNOS Donor Management Goals Registry Web Portal and linked to the Scientific Registry of Transplant Recipients (SRTR) for recipient outcomes. Recipients of biopsied donor livers (BxDL) were studied and a Cox proportional hazard analysis was used to identify independent predictors of 1-year graft survival.

RESULTS

Data from 5449 liver transplant recipients were analyzed, of which 1791(33%) received a BxDL. There was no difference in graft or patient survival between the non-BxDL and BxDL recipient groups. On adjusted analysis of BxDL recipients, macrosteatosis (21%-30%[n = 148] and >30%[n = 92]) was not found to predict 1-year graft survival, whereas increasing donor age (HR1.02), donor Hispanic ethnicity (HR1.62), donor INR (HR1.18), and recipient life support (HR2.29) were.

CONCLUSIONS

Excellent graft and patient survival can be achieved in recipients of BxDL grafts. Notably, as demonstrated by the lack of effect of macrosteatosis on survival, donor to recipient matching may contribute to these outcomes.

Temporal trends in utilization and outcomes of steatotic donor livers in the United States

Steatotic donor livers (SDLs) (macrosteatosis ≥30%) represent a possible donor pool expansion, but are frequently discarded due to a historical association with mortality and graft loss. However, changes in recipient/donor demographics, allocation policy, and clinical protocols might have altered utilization and outcomes of SDLs. We used Scientific Registry of Transplant Recipients data from 2005 to 2017 and adjusted multilevel regression to quantify temporal trends in discard rates (logistic) and posttransplant outcomes (Cox) of SDLs, accounting for Organ Procurement Organization-level variation. Of 4346 recovered SDLs, 58.0% were discarded in 2005, versus only 43.1% in 2017 (P < .001). SDLs were always substantially more likely discarded versus non-SDLs, although this difference decreased over time (adjusted odds ratio in 2005-2007:_13.15 15.28_17.74 ; 2008-2011:_11.77 13.41_15.29 ; 2012-2014:_9.87 11.37_13.10 ; 2015-2017:_7.79 8.89_10.15 , P < .001 for all). Conversely, posttransplant outcomes of recipients of SDLs improved over time: recipients of SDLs from 2012 to 2017 had 46% lower risk of mortality (adjusted hazard ratio [aHR]: _0.43 0.54_0.68 , P < .001) and 47% lower risk of graft loss (aHR: _0.42 0.53_0.67 , P < .001) compared to 2005 to 2011. In fact, in 2012 to 2017, recipients of SDLs had equivalent mortality (aHR: _0.90 1.04_1.21 , P = .6) and graft loss (aHR: _0.90 1.04_1.20 , P = .6) to recipients of non-SDLs. Increasing utilization of SDLs might be a reasonable strategy to expand the donor pool.

[Donor liver histology : Joint recommendations of the DGP, DTG and DSO]

BACKGROUND

The indications, implementation and reporting of liver biopsies for deceased organ donation are not mandatory or regulated. Reliable data on outcome quality and prognostic relevance are therefore not available. Defined standards are thus required to enable meaningful studies and to ensure high data quality of a national transplantation registry.

OBJECTIVE

Presentation of a synopsis of available studies and literature-based recommendations.

RESULTS AND CONCLUSION

Against the background of an organ shortage and a growing number of older donors, pretransplantation liver histology is of significant relevance to guide clinical decision making. With the joint recommendations of the German Transplantation Society (DTG), the German Society of Pathology (DGP) and the German Organ Transplantation Foundation (DSO) standardized procedures are defined for the first time.

The impact of postreperfusion syndrome during liver transplantation using livers with significant macrosteatosis

The impact of postreperfusion syndrome (PRS) during liver transplantation (LT) using donor livers with significant macrosteatosis is largely unknown. Clinical outcomes of all patients undergoing LT with donor livers with moderate macrosteatosis (30%-60%) (N = 96) between 2000 and 2017 were compared to propensity score matched cohorts of patients undergoing LT with donor livers with mild macrosteatosis (10%-29%) (N = 96) and no steatosis (N = 96). Cardiac arrest at the time of reperfusion was seen in eight (8.3%) of the patients in the moderate macrosteatosis group compared to one (1.0%) of the patients in the mild macrosteatosis group (P = .02) and zero (0%) of the patients in the no steatosis group (P = .004). Patients in the moderate macrosteatosis group had a higher rate of PRS (37.5% vs 18.8%; P = .004), early allograft dysfunction (EAD) (76.4% vs 25.8%; P < .001), renal dysfunction requiring continuous renal replacement therapy following transplant (18.8% vs 8.3%; P = .03) and return to the OR within 30 days (24.0% vs 7.3%; P = .002), than the no steatosis group. Both long-term patient (P = .30 and P = .08) and graft survival (P = .15 and P = .12) were not statistically when comparing the moderate macrosteatosis group to the mild macrosteatosis and no steatosis groups. Recipients of LT using livers with moderate macrosteatosis are at a significant increased risk of PRS. If patients are able to overcome the initial increased perioperative risk of using these donor livers, long-term graft survival does not appear to be different than matched recipients receiving grafts with no steatosis.

The Impact of Steatosis on the Outcome of Liver Transplantation: A Meta-Analysis

Background and Aims

Liver transplantation is one of the most effective treatments for end-stage liver disease as well as for cases of acute liver failure. Facing organ donor shortage, liver transplant teams had to use marginal organs. Thus, increasing availability is a key concern of donor liver grafts including steatotic livers. However, the use of steatotic liver is still controversial. The aim of this systematic review and meta-analysis was to analyze the impact of steatosis on the outcome of liver transplantation.

Methods

We searched PubMed, Cochrane Library, Embase, Web of knowledge, and so on for studies published through May 31, 2018, in which patients experienced liver transplantation using fatty liver. All studies extracted outcome indicators, and we draw conclusions by contrasting outcome indicators in different groups of steatosis. Odds ratios and 95% confidence intervals were calculated. P<0.05 was considered as statistically significant difference.

Results

19 publications were included. There was no significant difference between the group of no steatosis and mild group in primary nonfunction rate (P=0.605) or early graft dysfunction rate (P=0.44). The PNF rate was significantly higher in moderate group (P=0.003) and severe group (P <0.001) compared with that in no steatosis group. The same results were seen in early graft dysfunction rate. However, graft survival rate and patient survival rate did not differ between groups.

Conclusions

Livers with mild steatosis, even with moderate or severe steatosis, could be suitable donor under strict control of transplant conditions.

Systematic Evaluation of the Safety Threshold for Allograft Macrovesicular Steatosis in Cadaveric Liver Transplantation

Background: Currently, 30% macrovesicular steatosis (MaS) content is usually assigned empirically as the boundary between “use” and “refuse” a donor liver for liver transplantation (LT); however, this cut-off is questionable due to the lack of systemic evidence of the efficiency relative to prognosis prediction. Clinicians have tried to identify the threshold for optimized utilization of marginal steatotic allografts, but controversy exists among different studies.

Aim: Our study aimed to systematically determine an acceptable donor MaS content cut-off without incurring extra risk in liver transplantation, using meta-analysis.

Methods: The relevant literature reporting the relationship between MaS content and post-transplant mortality/morbidity was searched and retrieved in Pubmed, Embase, and ISI Web of Science.

Results: Nine studies were enrolled into the final analysis. A categorical comparison revealed that patients who received allografts with moderate steatosis (MaS content >30%) had significantly higher risks of graft failure/dysfunction, but not of mortality. Dose-response analysis showed that donor MaS content affected the graft failure/dysfunction in a non-linear relationship. Risks associated with MaS content in terms of poorer outcomes were independent of other risk covariates for liver transplantation. A non-significant increase in risk of inferior post-transplant outcomes was observed in patients who received allografts with a MaS content <35%. The risks of post-transplant graft failure and dysfunction increased with severe donor MaS content infiltration, without a consistent relationship.

Conclusions: The threshold of allograft MaS content can be safely extended to 35% without additional risk burden on post-transplant inferior outcomes. Clarification on “the effects of stratification” for MaS content can provide theoretical evidence for further optimal utilization of marginal steatotic allografts in liver transplantation.

Complement Activation in Liver Transplantation: Role of Donor Macrosteatosis and Implications in Delayed Graft Function

The complement system anchors the innate inflammatory response by triggering both cell-mediated and antibody-mediated immune responses against pathogens. The complement system also plays a critical role in sterile tissue injury by responding to damage-associated molecular patterns. The degree and duration of complement activation may be a critical variable controlling the balance between regenerative and destructive inflammation following sterile injury. Recent studies in kidney transplantation suggest that aberrant complement activation may play a significant role in delayed graft function following transplantation, confirming results obtained from rodent models of renal ischemia/reperfusion (I/R) injury. Deactivating the complement cascade through targeting anaphylatoxins (C3a/C5a) might be an effective clinical strategy to dampen reperfusion injury and reduce delayed graft function in liver transplantation. Targeting the complement cascade may be critical in donor livers with mild to moderate steatosis, where elevated lipid burden amplifies stress responses and increases hepatocyte turnover. Steatosis-driven complement activation in the donor liver may also have implications in rejection and thrombolytic complications following transplantation. This review focuses on the roles of complement activation in liver I/R injury, strategies to target complement activation in liver I/R, and potential opportunities to translate these strategies to transplanting donor livers with mild to moderate steatosis.

Transplant for the very sick: No limitations in donor quality?

When it comes to maximizing allograft function, the recipient is just as important as the liver graft itself. Whereas the “healthiest” of liver transplant candidates are likely to gain significant benefit from a liver graft of any quality, the sickest of candidates may still die despite transplantation with even an ideal liver. However, the very sick patients are precisely the ones who have the greatest need for liver transplantation—with any liver, regardless of quality—because they are most vulnerable to pretransplant death without one. How does one balance the urgent need for liver transplantation with optimization of the allograft’s function and utility for the very sick patient?

Donor Hepatic Steatosis Induce Exacerbated Ischemia-Reperfusion Injury Through Activation of Innate Immune Response Molecular Pathways

BACKGROUND

Severe liver steatosis is a known risk factor for increased ischemia-reperfusion injury (IRI) and poor outcomes after liver transplantation (LT). This study aimed to identify steatosis-related molecular mechanisms associated with IRI exacerbation after LT.

METHODS

Paired graft biopsies (n = 60) were collected before implantation (L1) and 90 minutes after reperfusion (L2). The LT recipients (n = 30) were classified by graft macrosteatosis: without steatosis (WS) of 5% or less (n = 13) and with steatosis (S) of 25% or greater (n = 17). Plasma samples were collected at L1, L2, and 1 day after LT (postoperative [POD]1) for cytokines evaluation. Tissue RNA was isolated for gene expression microarrays. Probeset summaries were obtained using robust multiarray average algorithm. Pairwise comparisons were fit using 2-sample t test. P values 0.01 or less were significant (false discovery rate <5%). Molecular pathway analyses were conducted using Ingenuity Pathway Analysis tool.

RESULTS

Significantly differentially expressed genes were identified for WS and S grafts after reperfusion. Comprehensive comparison analysis of molecular profiles revealed significant association of S grafts molecular profile with innate immune response activation, macrophage production of nitric oxide and reactive oxygen species, IL-6, IL-8, IL-10 signaling activation, recruitment of granulocytes, and accumulation of myeloid cells. Postreperfusion histological patterns of S grafts revealed neutrophilic infiltration surrounding fat accumulation. Circulating proinflammatory cytokines after reperfusion and 24 hours after LT concurred with intragraft-deregulated molecular pathways. All tested cytokines were significantly increased in plasma of S grafts recipients after reperfusion when compared with WS group at same time.

CONCLUSIONS

Increases of graft steatosis exacerbate IRI by exacerbation of innate immune response after LT. Preemptive strategies should consider it for safety usage of steatotic livers.

Clinical outcomes and costs associated with in-hospital biliary complications after liver transplantation: a cross-sectional analysis

INTRODUCTION

In-hospital biliary complications (BCs) after liver transplantation (LT) are reported in up to 20 % of patients and contribute to poor outcomes and increased costs. Existing single-center outcome and cost analyses studies are limited in scope.

METHODS

This is a cross-sectional analysis of national data involving 7,967 patients transplanted between 2011 and 2012 with the primary aim of determining the association between BCs and clinical outcomes and costs. Age, race, diagnosis, and severity of illness are associated with the development of BCs.

RESULTS

BCs develop in 14.6 % of LT recipients and have substantial implications for perioperative outcomes, including length of hospital and ICU stay (27.9 vs 19.6 mean days, p < 0.001 and 12.0 vs 8.3 mean days, p < 0.001, respectively), in-hospital morbidity (39 vs 27 %, p < 0.001), 30-day readmissions (14.8 vs 11.2 %, p < 0.001), and in-hospital mortality (5.8 vs 4.0 %, p < 0.001). BCs contributed to a mean increase in in-hospital costs of $36,212 (p < 0.001), due to increases in accommodations ($9,539, p < 0.001), surgical services ($3,988, p < 0.001), and pharmacy services ($8,445, p < 0.001).

DISCUSSION

BCs are a predominant etiology for in-hospital morbidity and mortality, while contributing significantly to the high cost of LT. Efforts should be focused on understanding salient and modifiable risk factors, while developing innovative strategies to reduce BCs.