Baseline and Center-Level Variation in Simultaneous Liver-Kidney Listing in the United States

Novel indications for referral and care for simultaneous liver kidney transplant recipients

PURPOSE OF REVIEW

Kidney dysfunction is challenging in liver transplant candidates to determine whether it is reversible or not. This review focuses on the pertinent data on how to best approach liver transplant candidates with kidney dysfunction in the current era after implementing the simultaneous liver kidney (SLK) allocation policy and safety net.

RECENT FINDINGS

The implementation of the SLK policy inverted the steady rise in SLK transplants and improved the utilization of high-quality kidneys. Access to kidney transplantation following liver transplant alone (LTA) increased with favorable outcomes. Estimating GFR in liver transplant candidates remains challenging, and innovative methods are needed. SLK provided superior patient and graft survival compared to LTA only for patients with advanced CKD and dialysis at least 3 months. SLK can provide immunological protection against kidney rejection in highly sensitized candidates. Post-SLK transplant care is complex, with an increased risk of complications and hospitalization.

SUMMARY

The SLK policy improved kidney access and utilization. Transplant centers are encouraged, under the safety net, to reserve SLK for liver transplant candidates with advanced CKD or dialysis at least 3 months while allowing lower thresholds for highly sensitized patients. Herein, we propose a practical approach to liver transplant candidates with kidney dysfunction.

Differential in Kidney Graft Years on the Basis of Solitary Kidney, Simultaneous Liver-Kidney, and Kidney-after-Liver Transplants

BACKGROUND

The number of simultaneous liver-kidney (SLK) transplants has significantly increased in the United States. There has also been an increase in kidney-after-liver transplants associated with 2017 policy revisions aimed to fairly allocate kidneys after livers. SLK and kidney-after-liver candidates are prioritized in allocation policy for kidney offers ahead of kidney-alone candidates.

METHODS

We compared kidney graft outcomes of kidney-alone transplant recipients with SLK and kidney-after-liver transplants using paired kidney models to mitigate differences among donor risk factors. We evaluated recipient characteristics between transplant types and calculated differential graft years using restricted mean survival estimates.

RESULTS

We evaluated 3053 paired donors to kidney-alone and SLK recipients and 516 paired donors to kidney-alone and kidney-after-liver recipients from August 2017 to August 2022. Kidney-alone recipients were younger, more likely on dialysis, and Black race. One-year and 3-year post-transplant kidney graft survival for kidney-alone recipients was 94% and 86% versus SLK recipients 89% and 80%, respectively, P < 0.001. One-year and 3-year kidney graft survival for kidney-alone recipients was 94% and 84% versus kidney-after-liver recipients 93% and 87%, respectively, P = 0.53. The additional kidney graft years for kidney-alone versus SLK transplants was 21 graft years/100 transplants (SEM=5.0) within 4 years post-transplantation, with no significant difference between kidney-after-liver and kidney-alone transplants.

CONCLUSIONS

Over a 5-year period in the United States, SLK transplantation was associated with significantly lower kidney graft survival compared with paired kidney-alone transplants. Most differences in graft survival between SLK and kidney-alone transplants occurred within the first year post-transplantation. By contrast, kidney-after-liver transplants had comparable graft survival with paired kidney-alone transplants.

Pros and Cons of the Safety Net Rule for Prioritization of Liver Transplant Recipients Who Receive Liver Alone Transplant but Develop End-Stage Renal Disease

The number of patients presenting with cirrhosis with kidney injury and the potential need for SLKT is increasing. In 2017, standardized criteria were implemented to identify candidates for SLKT as well as criteria for prioritizing LTA recipients for kidney transplant if they developed kidney failure, which is referred to as the 'safety net rule.' Goal of the safety net rule is to provide a pathway that provides increased priority to LTA recipients with renal failure who may have previously undergone SLKT. This article reviews the pros and cons of the safety net rule for liver transplant recipients who develop ESRD.

Textbook Outcome as a Quality Metric in Liver Transplantation

Quality in liver transplantation (LT) is currently measured using 1-y patient and graft survival. Because patient and graft survival rates now exceed 90%, more informative metrics are needed. Textbook outcomes (TOs) describe ideal patient outcomes after surgery. This study critically evaluates TO as a quality metric in LT.

Methods

United Network for Organ Sharing data for 25 887 adult LT recipients were used to define TO as patient and graft survival >1 y, length of stay ≤10 d, 0 readmissions within 6 mo, absence of rejection, and bilirubin <3 mg/dL between months 2 and 12 post-LT. Univariate analysis identified donor and recipient characteristics associated with TO. Covariates were analyzed using purposeful selection to construct a multivariable model, and impactful variables were incorporated as linear predictors into a nomogram. Five-year conditional survival was tested, and center TO rates were corrected for case complexity to allow for center-level comparisons.

Results

The national average TO rate is 37.4% (95% confidence interval, 36.8%-38.0%). The hazard ratio for death at 5 y for patients who do not experience TO is 1.22 (95% confidence interval, 1.11-1.34; P ≤ 0.0001). Our nomogram predicts TO with a C-statistic of 0.68. Center-level comparisons identify 31% of centers as high performing and 21% of centers as below average. High rates of TO correlate only weakly with center volume.

Conclusions

The composite quality metric of TO after LT incorporates holistic outcome measures and is an important measure of quality in addition to 1-y patient and graft survival.

Center variations in patient selection for simultaneous heart-kidney transplantation

There are no established regulations governing patient selection for simultaneous heart-kidney (SHK) transplantation, creating the potential for significant center-level variations in clinical practice.

METHODS

Using the United Network for Organ Sharing (UNOS) Standard Transplant Analysis and Research (STAR) file, we examined practice trends and variations in patient selection for SHK at the center level between January 1, 2004 and March 31, 2019.

RESULTS

Overall, SHK is becoming more common with most centers performing heart transplants also performing SHK. Among patients who underwent heart transplant who were receiving dialysis, the rate of SHK varied from 22% to 86% at the center level. Among patients not on dialysis, the median estimated glomerular filtration rate (eGFR) of patients receiving SHK varied between 19 and 59 mL/min/1.73 m² . When adjusting for other factors, the odds of SHK varied 57-fold between the highest and lowest SHK performing centers.

CONCLUSION

Variation in SHK at the center level suggests the need for national guidelines around the selection of patients for SHK.

Current State of Multiorgan Transplantation and Implications for Future Practice and Policy

The incidence of kidney dysfunction has increased in liver transplant and heart transplant candidates, reflecting a changing patient population and allocation policies that prioritize the most urgent candidates. A higher burden of pretransplant kidney dysfunction has resulted in a substantial rise in the utilization of multiorgan transplantation (MOT). Owing to a shortage of available deceased donor kidneys, the increased use of MOT has the potential to disadvantage kidney-alone transplant candidates, as current allocation policies generally provide priority for MOT candidates above all kidney-alone transplant candidates. In this review, the implications of kidney disease in liver transplant and heart transplant candidates is reviewed, and current policies used to allocate organs are discussed. Important ethical considerations pertaining to MOT allocation are examined, and future policy modifications that may improve both equity and utility in MOT policy are considered.

The impact of multi-organ transplant allocation priority on waitlisted kidney transplant candidates

Kidney-alone transplant (KAT) candidates may be disadvantaged by the allocation priority given to multi-organ transplant (MOT) candidates. This study identified potential KAT candidates not receiving a given kidney offer due to its allocation for MOT. Using the Organ Procurement and Transplant Network (OPTN) database, we identified deceased donors from 2002 to 2017 who had one kidney allocated for MOT and the other kidney allocated for KAT or simultaneous pancreas-kidney transplant (SPK) (n = 7,378). Potential transplant recipient data were used to identify the "next-sequential KAT candidate" who would have received a given kidney offer had it not been allocated to a higher prioritized MOT candidate. In this analysis, next-sequential KAT candidates were younger (p < .001), more likely to be racial/ethnic minorities (p < .001), and more highly sensitized than MOT recipients (p < .001). A total of 2,113 (28.6%) next-sequential KAT candidates subsequently either died or were removed from the waiting list without receiving a transplant. In a multivariable model, despite adjacent position on the kidney match-run, mortality risk was significantly higher for next-sequential KAT candidates compared to KAT/SPK recipients (hazard ratio 1.55, 95% confidence interval 1.44, 1.66). These results highlight implications of MOT allocation prioritization, and potential consequences to KAT candidates prioritized below MOT candidates.

Simultaneous liver kidney allocation policy and the Safety Net: an early examination of utilization and outcomes in the United States

Rates of simultaneous liver kidney (SLK) transplantation in the United States have progressively risen. On 8/10/17, the Organ Procurement and Transplantation Network implemented a policy defining criteria for SLK, with a "Safety Net" to prioritize kidney allocation to liver recipients with ongoing renal failure. We performed a retrospective review of the United Network for Organ Sharing (UNOS) database to evaluate policy impact on SLK, kidney after liver (KAL) and kidney transplant alone (KTA). Rates and outcomes of SLK and KAL transplants were compared, as was utilization of high-quality kidney allografts with Kidney Donor Profile Indices (KDPI) <35%. Here, SLK transplants comprised 9.0% and 4.5% of total postpolicy liver and kidney transplants compared to 10.2% and 5.5% prior. Policy enactment did not affect 1-year graft or patient survival for SLK and KAL populations. Less postpolicy SLK transplants utilized high-quality kidney allografts; in all transplant settings, outcomes using high-quality grafts remained stable. These findings suggest that policy implementation has reduced kidney allograft use in SLK transplantation, although both SLK and KAL rates have recently increased. Despite decreased high-quality kidney allograft use, SLK and KAL outcomes have remained stable. Additional studies and long-term follow-up will ensure optimal organ access and sharing.

Early Kidney Allograft Failure After Simultaneous Liver-kidney Transplantation: Evidence for Utilization of the Safety Net?

BACKGROUND

With the implementation of the "Safety Net," we aimed to determine the impact of simultaneous liver-kidney transplantation (SLKT), as compared to kidney transplant after liver transplant (KALT), on kidney allograft failure (KF).

METHODS

An analysis of the UNOS database for all adult patients who received either an SLKT or KALT from 2002 to 2017. The outcomes were 90-day KF and 1-year KF (as reported to UNOS, at 90- and 365-day postkidney transplant, respectively). We compared the following groups of patients: SLKT <25 (SLKT with final model for end-stage liver disease [MELD] <25), SLKT25/35 (MELD ≥25/<35), and SLKT35 (MELD ≥35) to KALT.

RESULTS

Of the 6276 patients, there were 1481 KALT, 1579 SLKT <25, 1832 SLKT25/35, and 1384 SLKT ≥35. The proportion of patients with 90-day and 1-year KF increased significantly among the KALT, SLKT <25, SLKT25/35, and SLKT ≥35 groups (P < 0.001; test for trend): 90-day KF: 3.3% versus 5.5% versus 7.3% versus 9.3% and 1-year KF: 5.1% versus 9.4% versus 12.3% versus 14.7%. After adjustment and compared with KALT, beginning at an MELD ≥25 those undergoing SLKT had significantly higher risk of 90-day and 1-year KF: 90-day KF: SLKT25/35: hazard ratio, 1.6(1.0-2.3); SLKT ≥35: 2.1(1.3-3.3); 1-year KF: SLKT25/35: hazard ratio, 1.7(1.2-2.4); SLKT ≥35: 2.1(1.5-3.0).

CONCLUSIONS

As compared to KALT recipients, SLKT recipients with an MELD ≥25 had significantly higher risk of early KF. Given the now well-established "Safety Net," KALT may serve as an opportunity to improve kidney outcomes in patients with an MELD ≥25.

Delayed kidney transplantation in combined liver-kidney transplantation

PURPOSE OF REVIEW

To review the impact of delayed kidney transplantation approach in combined (simultaneous) liver-kidney transplantation (CLKT).

RECENT FINDINGS

CLKT offers a life-saving procedure for patients with both end-stage liver disease and chronic kidney disease or prolonged acute kidney injury. It is the most common multiorgan transplant procedure in the US accounting for 9-10% of all liver transplants performed. The number of CLKT has also been increasing in other countries with a better understanding of hepato-renal syndrome. US is the only country which implemented a national allocation policy for CLKT in 2017. Due to the different physiological needs of liver and kidney allografts immediately after transplantation, delayed kidney transplantation approach in CLKT has been introduced for the first time by the Indiana Group, naming it as 'the Indiana Approach'. Over the years, many other groups in the US and in Europe published better outcomes in CLKT using the delayed kidney transplantation approach with the support of hypothermic machine perfusion.

SUMMARY

Several groups have shown that delayed kidney transplantation in CLKT is a safe procedure with better outcomes in graft(s) and patient survival.

Association of balanced abdominal organ transplant center volumes with patient outcomes

BACKGROUND

The volume-outcome relationship for organ-specific transplantation is well-described; it is unknown if the relative balance of kidney compared with liver volumes within an institution relates to organ-specific outcomes. We assessed the association between relative balance within a transplant center and outcomes.

METHODS

National retrospective analysis of isolated kidney and liver transplants in United States 2005-2014 followed through 2019. Latent class analysis defined transplant center phenotypes. Multivariate Cox models estimated death-censored graft loss and mortality.

RESULTS

Latent class analysis identified four phenotypes: kidney only (n = 117), kidney dominant (n = 36), mixed/balanced (n = 90), and liver dominant (n = 13). Compared to mixed centers, the risk of kidney graft loss was higher at kidney-dominant (HR 1.07, p < .001) and liver-dominant (HR 1.10, p < .001) centers, while kidney-only (HR 1.06, p = .01) centers had higher mortality. Liver graft loss was not associated with phenotype, but risk of patient death was lower (HR 0.93, p = .02) at liver dominant and higher (HR 1.06, p = .02) at kidney-dominant centers.

CONCLUSIONS

A mixed phenotype was associated with improved kidney transplant outcomes, whereas liver transplant outcomes were best at liver-dominant centers. While these findings need to be verified with center-level resources, optimization of shared resources could improve patient and organ outcomes.

Hepatorenal Syndrome

Development of acute kidney injury in patients with chronic liver disease is common and portends a poor prognosis. Diagnosis remains challenging, as traditional markers, such as serum creatinine, are not reliable. Recent development of novel biomarkers may assist with this. Pathophysiology of this condition is multifactorial, relating to physiologic changes associated with portal hypertension, kidney factors, and systemic inflammatory response. Mainstay of treatment remains use of vasoconstrictors along with albumin. Recent guidelines streamline the selection of patients that will require simultaneous liver and kidney transplantation. Posttransplant kidney injury is common relating to multiple factors.

New OPTN Simultaneous Liver-Kidney Transplant (SLKT) Policy Improves Racial and Ethnic Disparities

(1) Background: On 10 August 2017, the Organ Procurement and Transplantation Network (OPTN) adopted standardized eligibility criteria to properly determine which transplant candidates should undergo Simultaneous Liver-Kidney Transplant (SLKT). Racial and ethnic disparities have not been examined after 2017. Therefore, using the United Network for Organ Sharing (UNOS), we aim to evaluate post-graft survival outcomes among Caucasians, African Americans, and Hispanics. (2) Methods: Kaplan-Meier curves and Cox regression models are used to compare post-transplant graft survival for Caucasians, African Americans (AAs), and Hispanics. Competing risk analysis is used to evaluate the cumulative incidence of death or re-transplantation with re-transplantation and death as competing risks. (3) Results: On multivariate Cox regression analysis, no differences in graft survival are found in AA (hazard ratio (HR): 1.30; 95% CI: 0.74-2.29 p = 0.354) or Hispanics (HR: 1.18; 95% CI: 0.70-2 p = 0.520) compared to Caucasians after 2017. On competing risk analysis of the risk of death with re-transplantation as a competing risk, no difference is found between ethnic minorities after 2017. There is a similar finding from competing risk analysis of the risk of re-transplantation with death as a competing risk. (4) Conclusion: After introducing standardized eligibility criteria for SLKT allocation, the post-graft survival outcomes remain similar between the different racial and ethnic groups, displaying the benefits of adopting such policy in 2017.

Delayed Graft Function in Simultaneous Liver Kidney Transplantation

BACKGROUND

Delayed graft function (DGF) is associated with inferior posttransplant outcomes in kidney transplantation. Given these adverse outcomes, we sought to determine the incidence, unique risk factors, and posttransplant outcomes for simultaneous liver kidney (SLK) transplant recipients developing DGF.

METHODS

We studied 6214 adult SLK recipients from March 2002 to February 2017 using the Scientific Registry of Transplant Recipients. We determined associations between risk factors and DGF using Poisson multivariate regression and between DGF and graft failure and mortality using Cox proportional hazard analysis.

RESULTS

The overall rate of DGF was 21.8%. Risk factors for DGF in the hepatitis C virus (HCV)-negative recipient population included pretransplant dialysis (adjusted incident rate ratio [aIRR] 3.26, P = 0.004), donor body mass index (aIRR 1.25 per 5 kg/m, P = 0.01), and transplantation with a donation after circulatory death (aIRR 5.38, P = 0.001) or imported donor organ (regional share aIRR 1.69, P = 0.03; national share aIRR 4.82, P < 0.001). DGF was associated with a 2.6-fold increase in kidney graft failure (adjusted hazard ratio [aHR] 2.63, P < 0.001), 1.6-fold increase in liver graft failure (aHR 1.62, P < 0.001), and 1.6-fold increase in mortality (aHR 1.62, P < 0.001).

CONCLUSIONS

In HCV-negative SLK recipients, recipient pretransplant dialysis and components of kidney graft quality comprise significant risk factors for DGF. Regardless of HCV status, DGF is associated with inferior posttransplant outcomes. Understanding these risk factors during clinical decision-making may improve prevention of DGF and may represent an opportunity to improve posttransplant outcomes.

Trends and Outcomes in Simultaneous Liver and Kidney Transplantation in Australia and New Zealand

AIM

Rates of simultaneous liver and kidney transplantation (SLKT) have increased, but indications for SLKT remain poorly defined. Additional data are needed to determine which patients benefit from SLKT to best direct use of scarce donor kidneys.

METHODS

Data were extracted from the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) database for all SLKT performed until the end of 2017. Patients were divided by pretransplant dialysis status into no dialysis before SLKT (preemptive kidney transplant) and any dialysis before SLKT (nonpreemptive). Baseline characteristics and outcomes were compared.

RESULTS

Between 1989 and 2017, inclusive, 84 SLKT procedures were performed in Australia, of which 24% were preemptive. Preemptive and nonpreemptive SLKT recipients did not significantly differ in age (P = .267), sex (P = .526), or ethnicity (P = .870). Over a median follow-up time of 4.5 years, preemptively transplanted patients had a statistically equivalent risk of kidney graft failure (hazard ratio (HR) 1.83, 95% confidence interval [CI]: 0.36-12.86, P = .474) and all-cause mortality (HR 1.69, 95% CI: 0.51-5.6, P = .226) compared to nonpreemptive patients. Overall, 1- and 5-year survival rates for all SLKTs were 92% (95% CI: 86-96) and 60% (95% CI: 45-75), respectively.

CONCLUSION

Kidney graft and overall patient survival were similar between patients with preemptive kidney transplant and those who were dialysis dependent.

Chronic Kidney Disease in Liver Transplant Candidates: A Rising Burden Impacting Post-Liver Transplant Outcomes

The burden of chronic kidney disease (CKD) is rising among patients with cirrhosis, though it is not known what impact this has had on outcomes after liver transplantation (LT). All patients listed for LT in the United States between 2002 and 2017 were analyzed, excluding those listed with Model for End-Stage Liver Disease (MELD) exceptions. The primary outcome was post-LT mortality. We defined pre-LT CKD as an estimated glomerular filtration rate <60 mL/minute for 90 days or ≥42 days of hemodialysis. Cox regression determined the association between pre-LT CKD and post-LT mortality. Of 78,640 LT candidates, the proportion with CKD among LT recipients increased from 7.8% in 2002 to 14.6% in 2017 (test for trend, P < 0.001). Among the 39,719 LT recipients, pre-LT CKD was significantly associated with post-LT mortality (hazard ratio [HR], 1.16; P < 0.001) even after adjusting for donor risk index (DRI), age, MELD, etiology, hepatic encephalopathy, simultaneous liver-kidney transplantation (SLKT), and diabetes. There was no mediating influence of SLKT on the effect of pre-LT CKD on post-LT survival (P > 0.05). Therefore, pre-LT CKD has a deleterious impact on post-LT outcomes, which is an impact that is not mediated through SLKT. These findings highlight the need for the identification of CKD when preventative measures are possible.

Current status of combined liver-kidney transplantation

Combined liver-kidney transplantation is a life-saving procedure for patients with end-stage liver disease and underlying chronic kidney disease, or prolonged acute kidney injury. Due to physiologic changes secondary to portal hypertension in patients with end-stage liver disease, kidney injury is common, and combined liver-kidney transplantation accounts for 10% of all the liver transplants performed in the United States. Recently implemented policy in the United States standardizes the medical criteria for eligibility, and introduces a 'safety net' for those who are transplanted with a liver graft alone, in order to be able to receive a kidney graft later. Increasing number of combined liver-kidney transplants provides a large cohort of patients to be studied in detail for identification of factors (both donor and recipient-related) associated with better outcomes. Data regarding the safety and efficacy of delaying the kidney transplant part of the combined liver-kidney transplantation, and the immunologic benefits of the multi-organ transplantations including the liver are emerging. Here, we review the most recent analyses, and provide our opinion regarding the best practices in combined liver-kidney transplantation based on the evidence.

Outcomes of Liver Transplantation in Patients on Renal Replacement Therapy: Considerations for Simultaneous Liver Kidney Transplantation Versus Safety Net

As the liver transplant (LT) waiting list continues to outpace organ availability, many patients require renal replacement therapy (RRT) before LT. It is unclear which patients will benefit from simultaneous liver kidney (SLK) transplant as opposed to awaiting a Safety Net kidney transplant (KT) post-LT.

Methods

In this study, a retrospective analysis of the United Network for Organ Sharing dataset was performed to identify risk factors associated with poor outcome for patients on RRT before LT who were listed for SLK and received either SLK vs LT alone (LTA).

Results

Between January 2003 and December 2016, 8971 adult LT recipients were on RRT at the time of LT. 5359 were listed for and received LTA (Group 1). Of 3612 patients listed for SLK, 3414 (38.1%) received SLK (Group 2) and 198 (2.2%) received LTA (Group 3). Overall, Group 3 had lower graft and patient survival post-LT when compared with Groups 1 and 2 (P < 0.001). Serum creatinine at 1 year post-LT and cumulative incidence for KT at 3 years post-LT were higher for Group 3 (P < 0.001). On multivariate analysis, pre-LT diabetes (P = 0.002), Model of End-Stage Liver Disease score (P = 0.01), and donor kidney donor profile index (P = 0.025) were significant in Group 2. Recipient age >60 (P < 0.001) and RRT pre-LT (>90 days; P = 0.001) were associated with lower patient survival in Group 3.

Conclusions

Among LT recipients on RRT before LT who were listed for SLK, RRT >90 days, and age >60 were associated with poor outcome following LTA. This suggests that programs should carefully weigh the decision to proceed with LTA vs waiting for SLK in this patient population. Future access to Safety Net KT will be an important consideration for these patients moving forward.

Direct-acting antiviral regimens are safe and effective in the treatment of hepatitis C in simultaneous liver-kidney transplant recipients

Hepatitis C (HCV) remains the single most common etiology of end-stage liver disease leading to simultaneous liver/kidney transplant (SLKT) and has worse post-transplant survival compared to non-HCV patients. We aim to assess the effectiveness and tolerance of the all-oral direct-acting antiviral (DAA) agents with or without ribavirin (RBV) in the treatment of HCV recurrence post-SLKT. Thirty-four patients were studied retrospectively, composed predominantly of treatment-naïve (73.5%) non-Caucasian (61.8%) males (82.4%) infected with genotype 1a (64.7%). 94.1% reached a sustained virologic response (SVR) after 24 weeks (32/34 patients), without difference between 12 and 24 weeks of therapy. 64.7% had no clinical side effects. Three deaths occurred, all unrelated to treatment. One patient had liver rejection; tacrolimus was increased and prednisone was initiated while HCV treatment was continued and the patient ultimately achieved SVR. No liver graft losses. No kidney rejection or losses. We demonstrated that DAA combinations with or without RBV result in a remarkable SVR rate and tolerated in the majority of the studied SLKT patients. It is safe to wait to treat until post-kidney transplant and therefore increase the donor pool for these patients. Our cohort is ethnically diverse, making our results generalizable.