A Paired Kidney Analysis of Multiorgan Transplantation: Implications for Allograft Survival

Simultaneous Liver and Kidney Transplantation in Patients Aged 70 y and Older: Proceed With Caution

Background

The number of elderly patients aged 70 y and older with liver and kidney failure is increasing, mainly because of increasing prevalence of metabolic dysfunction-associated steatohepatitis. At present, limited data are available on the outcomes of elderly patients who fit the criteria for dual organ transplantation since the implementation of the simultaneous liver and kidney (SLK) allocation policy.

Methods

We performed a retrospective analysis of the Organ Procurement and Transplantation Network database of adults aged 18 y and older undergoing SLK and kidney transplantation only from August 11, 2017, to December 31, 2022. We examined patient and graft survivals and compared the outcomes of the recipients aged 70 y and older undergoing SLK transplantation to those who received kidney transplant alone and kidney after liver transplant.

Results

During the study period, there has been a significant rise in the number of patients aged 70 y and older undergoing SLK transplantation, with 6 patients undergoing SLK transplantation in 2017 and 63 in 2021. Patients aged 70 y and older had significantly lower survival with 82.9% at 1 y and 66.5% at 3 y compared with 89.3% and 78.8% in the 50-69 y age group and 93.2% and 88.6% in the 18-49 y age group, respectively. Overall, kidney allograft survival was significantly lower in the 70 y and older group, with 80.9% at 1 y and 66.4% at 3 y compared with 91.1% and 75.5%, respectively, in those undergoing kidney transplant alone. There was no difference in kidney allograft survival in those undergoing SLK and kidney after liver transplantation.

Conclusions

Although the outcomes are inferior in recipients of SLK transplant aged 70 y and older, chronologic age should not preclude them from undergoing transplantation. Kidney transplantation after liver transplantation could be considered to avoid futile transplants.

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.

High Rate of Kidney Graft Failure after Simultaneous Heart-Kidney Transplantation

Key Points

Simultaneous heart–kidney transplant is associated with high rates of kidney graft failure which are worse when compared with kidney transplant alone. The major causes of kidney graft failure in simultaneous heart–kidney transplant recipients were patient death and primary nonfunction of kidney graft.

Background

The indications and outcomes of simultaneous heart–kidney transplantation (SHKT) remain suboptimally defined. Risk factors for renal graft failure after SHKT also remain poorly defined.

Methods

We analyzed the renal graft outcomes among SHKT recipients using United Network for Organ Sharing database from 2015 to 2020. To evaluate for factors associated with poor renal outcomes, we compared SHKT and kidney transplantation alone recipients using propensity score matching.

Results

Among SHKT recipients, the rate of primary nonfunction (PNF) of kidney graft was 3%, the 30-day kidney graft failure rate was 7.0%, and the 30-day post-transplant mortality rate was 4.1%. The incidence of kidney delayed graft function was 27.5%. Kidney graft failure was seen early post-SHKT with most common causes of patient death (43.9%) and PNF of kidney graft (41.5%). One- and 2-year patient survival was 89.2% and 86.5%, and 1- and 2-year freedom from kidney graft failure was 85.4% and 82.7%, respectively. In subgroup analysis of SHKT recipients, use of pretransplant mechanical cardiac support (adjusted odds ratio [aOR], 2.57; P = 0.017), higher calculated panel reactive antibody (aOR, 1.76; P = 0.016), and older donor age per 10 years (aOR, 1.94; P = 0.001) were associated with PNF. Pretransplant extracorporeal membrane oxygenation support was associated with the increased risk of 30-day recipient mortality (aOR, 5.55; P = 0.002). Increased 30-day graft failure was seen in SHKT recipients with pretransplant mechanical cardiac support (aOR, 1.77; P = 0.038) and dialysis at the time of transplant (aOR, 1.72; P = 0.044). Multivariable Cox hazard analysis demonstrated that SHKT, when compared with kidney transplantation alone, is associated with increased kidney graft failure (hazard ratio, 2.56; P < 0.001) and recipient mortality (hazard ratio, 2.65; P < 0.001).

Conclusions

SHKT is associated with high rates of kidney graft failure. Identification of risk factors of renal graft failure can help optimize recipient selection for SHKT versus kidney after heart transplantation, especially after introduction of the new safety-net policy.

Renal Function in Receptors With Simultaneous Liver-Kidney Transplant From the Same Donor

Controversy surrounds the suitability of simultaneous liver-kidney transplant (SLKT) when compared with sequential transplant. Pretransplant renal failure is a post-transplant mortality predictor, and studies demonstrate worse functioning and lower survival of the renal graft when compared with kidney transplant alone (KTA).

BACKGROUND

This study compares renal function in patients with SLKT and those who received the contralateral kidney from the same donor.

MATERIAL AND METHODS

From June 2017 to February 2021, 5 SLKTs were performed in our hospital, and contralateral kidney grafts took place in other Andalusian Modification on Diet in Renal Disease-4 hospitals. Renal function was assessed according to glomerular filtration (GF) by the formula (that uses 4 variables: creatinine, age, sex, and race) during different periods of time; and the average increase of GF during 6 months in both groups was compared. Other factors from donors and receptors were also compared.

RESULTS

No statistically significant differences between average GF in both groups were found; however, there were statistically significant differences when we compared the GF increase 6 months after the transplant in both groups of patients, being that increase higher in patients with KTA.

CONCLUSIONS

Despite our small sample size, our study found that patients with SLKT have worse functioning of the kidney graft than those with KTA.

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.

Kidney After Liver Transplantation Matched-pair Analysis: Are Kidneys Allocated to Appropriate Patients to Maximize Their Survival?

BACKGROUND

Kidney after liver transplantation (KALT) is the best therapeutic option for patients with end-stage renal disease after orthotopic liver transplantation (OLT). New allocation policies prioritize kidneys to patients in renal failure within the first year following OLT. There is little data on how kidney quality, measured by kidney donor profile index (KDPI), impacts KALT survival outcomes.

METHODS

The United Network for Organ Sharing database was queried for adult KALT recipients from 1988 to 2015 and compared to their paired kidney transplant alone (KTA) recipients. Seven hundred forty-five pairs were stratified into 3 KDPI subgroups and compared patient survival, graft survival, and death-censored graft survival among matched-paired recipients.

RESULTS

Overall, KTA recipients had superior patient and graft survival compared with the KALT group. KTA patient survival was superior for all 3 KDPI subgroups analysis. KTA graft survival was superior compared with KALT recipients of KDPI 21%-85% kidneys. Inferior graft half-life was observed in KALT versus KTA recipients with KDPI 21%-85% and >85%.

CONCLUSIONS

From a utilitarian perspective, it is important that kidneys are allocated to recipients that are able to maximize their benefit from the full life of the organ. In KTA recipients, graft quality correlates directly to graft survival. However, in KALT patients receiving the matched-pair kidneys of the KTA recipients, patient mortality, rather than kidney quality, dictates graft survival significantly. As allocation practices continue developing, utilization of expanded criteria kidneys that better match anticipated patient and graft survival should be strongly considered to maximize the benefits of limited resources for the greatest number of patients.

Defining a Willingness-to-transplant Threshold in an Era of Organ Scarcity: Simultaneous Liver-kidney Transplant as a Case Example

BACKGROUND

Organ scarcity continues in solid organ transplantation, such that the availability of organs limits the number of people able to benefit from transplantation. Medical advancements in managing end-stage organ disease have led to an increasing demand for multiorgan transplant, wherein a patient with multiorgan disease receives >1 organ from the same donor. Current allocation schemes give priority to multiorgan recipients compared with single-organ transplant recipients, which raise ethical questions regarding equity and utility.

METHODS

We use simultaneous liver and kidney (SLK) transplant, a type of multiorgan transplant, as a case study to examine the tension between equity and utility in multiorgan allocation. We adapt the health economics willingness-to-pay threshold to a solid organ transplant setting by coining a new metric: the willingness-to-transplant (WTT) threshold.

RESULTS

We demonstrate how the WTT threshold can be used to evaluate different SLK allocation strategies by synthesizing utility and equity perspectives.

CONCLUSIONS

We submit that this new framework enables us to distill the question of SLK allocation down to: what is the minimum amount of benefit we require from a deceased donor kidney to allocate it for a particular indication? Addressing the above question will prove helpful to devising a rational system of SLK allocation and is applicable to other transplant settings.

Ethical decision-making in simultaneous heart-liver transplantation

PURPOSE OF REVIEW

Simultaneous heart-liver (SHL) transplants are only a small proportion of overall heart and liver transplantation, they have been increasing in frequency and thus challenge the equitable allocation of organs.

RECENT FINDINGS

The incidence of SHL transplants is reviewed along with the outcomes of SHL transplants and their impact on the waitlist, particularly in the context of solitary heart and liver transplantation. The ethical implications, most importantly the principles of utility and equity, of SHL transplant are addressed. In the context of utility, the distinction of a transplant being life-saving versus life-enhancing is investigated. The risk of hepatic decompensation for those awaiting both solitary and combined organ transplantation is an important consideration for the principle of equity. Lastly, the lack of standardization of programmatic approaches to SHL transplant candidates, the national approach to allocation, and the criteria by which programs are evaluated are reviewed.

SUMMARY

As with all multiorgan transplantation, SHL transplantation raises ethical issues of utility and equity. Given the unique patient population, good outcomes, lack of alternatives, and overall small numbers, we feel there is continued ethical justification for SHL, but a more standardized nationwide approach to the evaluation, listing, and allocation of organs is warranted.

To kidney or not to kidney: Applying lessons learned from the simultaneous liver-kidney transplant policy to simultaneous heart-kidney transplantation

As the medical community is increasingly offering transplantation to patients with increasing comorbidity burdens, the number of simultaneous heart-kidney (SHK) transplants is rising in the United States. How to determine eligibility for SHK transplant versus heart transplant alone is unknown. In this review, we situate this problem in the broader picture of organ shortage. We critically appraise available literature on outcomes in SHK versus heart transplant alone. We posit staged kidney-after-heart transplantation as a plausible alternative to SHK transplantation and review the pros and cons. Drawing lessons from the field of simultaneous liver-kidney transplant, we argue for an analogous policy for SHK transplant with standardized minimal eligibility criteria and a modified Safety Net provision. The new policy will serve as a starting point for comparing simultaneous versus staged approaches and refining the medical eligibility criteria for SHK.

Changes in Simultaneous Liver-kidney Transplant Allocation Policy May Impact Postliver Transplant Outcomes

BACKGROUND

Previous simultaneous liver-kidney (SLK) transplant allocation was based on serum creatinine, a metric that disadvantaged women relative to men. A recent SLK transplant policy change uses estimated glomerular filtration rate (eGFR), which accounts for sex-based differences in creatinine.

METHODS

To understand the impact of this new policy, we analyzed nonstatus 1 adults listed for liver transplantation (LT) from May 2007 to July 2014, excluding those with exceptions. We defined patients who met the new SLK policy as having an eGFR <60 mL/min for 90 days, with a final eGFR <30 mL/min.

RESULTS

Of 40979 candidates, 1683 would have met only the new criteria (N-SLK), 2452 would have met only the old criteria (O-SLK), and 1878 would have met both criteria (B-SLK). Compared to those in the B-SLK or O-SLK groups, those in the N-SLK group were significantly more likely to be female (52% versus 36% versus 39%, P < 0.001). Cox-regression analysis demonstrated that in adjusted analysis those in the N-SLK group were significantly less likely to die postliver transplant (hazard ratio [HR], 0.0; P < 0.001). Further, in Cox regression subgroup analyses, both in women (HR 0.04; P < 0.001) and in men (HR, 0.02, P < 0.001) those in the N-SLK group who underwent liver transplant were significantly less likely to die postliver transplant, even after adjustment for confounders.

CONCLUSIONS

We anticipate that implementation of the new SLK policy will increase the proportion of women and decrease the proportion of men who are listed for SLK but may not improve posttransplant survival. Our data highlight the need for monitoring of SLK outcomes after implementation of the new policy.

Current Status of Simultaneous Liver-Kidney Transplantation in the United States

On August 10, 2017, a formal policy was enacted in the United States that defined listing criteria for simultaneous liver-kidney transplantation and priority for patients who received a liver transplantation (LT) and subsequently developed significant kidney disease after LT. This article reviews and summarizes the rationale for such policies, the policies themselves, and the potential impact on LT candidates.

Effect of Renal Diagnosis on Survival in Simultaneous Liver-Kidney Transplantation

BACKGROUND

Simultaneous liver-kidney transplantation is lifesaving, however, the utility of allocating 2 organs to a single recipient remains controversial, particularly in the face of potentially inferior survival. This study aims to determine the effect of renal indication for transplantation on simultaneous liver-kidney transplantation outcomes.

METHODS

All adult recipients of combined whole liver-kidney transplants in the United Network for Organ Sharing database from 2003 to 2016 with a renal diagnosis of hypertension (HTN), diabetes mellitus (DM), acute tubular necrosis (ATN), or hepatorenal syndrome (HRS) were examined. Comparisons were made between the HTN/DM group and the ATN/HRS group using standard statistical methods.

RESULTS

There were 1,204 patients in the HRS/ATN group vs 1,272 patients in the HTN/DM group. The HTN/DM patients were slightly older (58.1 vs 56.4 years; p < 0.001), more likely to have liver disease due to chronic viral hepatitis (33.2% vs 21.5%; p < 0.001), and less acutely ill (mean Model for End-Stage Liver Disease score of 27.2 vs 33.1; p < 0.001) than their HRS/ATN counterparts. The prevalence of nonalcoholic steatohepatitis was 16.8% in both groups. Donor demographics were similar in both groups, although HTN/DM patients were more likely to have a local (81.6% vs 67.7%; p < 0.001) rather than regional donor. Patient survival rates at 1, 3, and 5 years were significantly lower in the HTN/DM group (87.4%, 78.2%, and 71.2% vs 90.7%, 84.1%, and 76.6%, respectively). Median survival was 118 months for the HTN/DM group vs 139.7 months for the HRS/ATN (p < 0.001). The HTN/DM patients were at significantly higher risk of death (hazard ratio 1.533; p < 0.001), liver graft loss (hazard ratio 1.611; p < 0.001), and renal graft loss (hazard ratio 1.592; p < 0.001) than ATN/HRS patients on multivariable analysis.

CONCLUSIONS

Despite a lower acuity of illness, HTN/DM patients have inferior survival after simultaneous liver-kidney transplantation than those with ATN/HRS. This should be considered in risk adjustment and allocation schemes.

Refining the Role of Simultaneous Liver Kidney Transplantation

Adoption of the model for end-stage liver disease score by Organ Procurement and Transplant Network (OPTN) deceased donor liver allocation policy in 2002 has led to an increase in the number of simultaneous liver kidney (SLK) transplantation. Since kidney function recovery following liver transplantation is difficult to predict, allocation of the kidney for SLK transplantation thus far has not been based on much rationale and evidence. Lack of OPTN policy towards SLK organ allocation has resulted in great variations among transplant centers regarding SLK transplantation. Increasing use of kidneys towards SLK transplantation diverts deceased donor kidneys away from candidates awaiting kidney-alone transplantation. Recently OPTN/United Network of Organ Sharing has implemented medical eligibility criteria for adult SLK transplantation which also includes a concept of safety net. Implementation of the new policy is a move in a positive direction, providing consistency in our practice and evidence-based guidelines in selecting candidates for SLK transplantation. This policy needs to be monitored prospectively and modified based on new data that will emerge over time. This review outlines the literature on SLK transplantation and efforts towards developing rational policy on SLK organ allocation.

Utility in Treating Kidney Failure in End-Stage Liver Disease With Simultaneous Liver-Kidney Transplantation

Background

Simultaneous liver-kidney (SLK) transplantation plays an important role in treating kidney failure in patients with end-stage liver disease. It used 5% of deceased donor kidney transplanted in 2015. We evaluated the utility, defined as posttransplant kidney allograft lifespan, of this practice.

Methods

Using data from the Scientific Registry of Transplant Recipients, we compared outcomes for all SLK transplants between January 1, 1995, and December 3, 2014, to their donor-matched kidney used in kidney-alone (Ki) or simultaneous pancreas kidney (SPK) transplants. Primary outcome was kidney allograft lifespan, defined as the time free from death or allograft failure. Secondary outcomes included death and death-censored allograft failure. We adjusted all analyses for donor, transplant, and recipient factors.

Results

The adjusted 10-year mean kidney allograft lifespan was higher in Ki/SPK compared with SLK transplants by 0.99 years in the Model for End-stage Liver Disease era and 1.71 years in the pre-Model for End-stage Liver Disease era. Death was higher in SLK recipients relative to Ki/SPK recipients: 10-year cumulative incidences 0.36 (95% confident interval 0.33-0.38) versus 0.19 (95% confident interval 0.17-0.21).

Conclusions

SLK transplantation exemplifies the trade-off between the principles of utility and medical urgency. With each SLK transplantation, about 1 year of allograft lifespan is traded so that sicker patients, that is, SLK transplant recipients, are afforded access to the organ. These data provide a basis against which benefits derived from urgency-based allocation can be measured.

This analysis of the UNOS data demonstrated that SLK patients had decreased long term renal graft function that SPK patients. This analysis demonstrates the difficult policy choices epitomized by prioritizing the SLK population and its impact of utility considerations. Supplemental digital content is available in the text.

New Organ Allocation System for Combined Liver-Kidney Transplants and the Availability of Kidneys for Transplant to Patients with Stage 4-5 CKD

A new proposal has been created for establishing medical criteria for organ allocation in recipients receiving simultaneous liver-kidney transplants. In this article, we describe the new policy, elaborate on the points of greatest controversy, and offer a perspective on the policy going forward. Although we applaud the fact that simultaneous liver-kidney transplant activity will now be monitored and appreciate the creation of medical criteria for allocation in simultaneous liver-kidney transplants, we argue that some of the criteria proposed, especially those for allocating a kidney to a liver recipient with AKI, are too liberal. We call on the nephrology community to follow the consequences of this new policy and push for a re-examination of the longstanding policy of allocating kidneys to multiorgan transplant recipients before all other candidates. The charge to protect our system of equitable organ allocation is very challenging, but it is a challenge that we must embrace.