Changes in united network for organ sharing policy for simultaneous liver‐kidney allocation

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Abbreviations

eGFR

estimated glomerular filtration rate

HLA

human leukocyte antigen

KDPI

kidney donor profile index

OPTN

Organ Procurement and Transplantation Network

SLK

simultaneous liver‐kidney transplantation

Renal insufficiency is a frequent complication among patients with end‐stage liver disease, afflicting nearly 20% of patients on the liver transplant wait list.1 The coincidence of renal disease in the liver transplant population has been principally driven by the use of the Model for End‐Stage Liver Disease score for deceased donor liver allocation, which relies heavily on serum creatinine. Although in most circumstances liver allograft recipients recover renal function, the minority of patients with persistent renal disease (5% cumulative risk after liver transplant over 5 years) have greater rates of allograft loss and postoperative mortality.2 Clinical predictive factors that delineate those patients unlikely to recover renal function posttransplant are largely unknown to date.3, 4, 5, 6 Given this uncertainty, a trend toward wider utilization of simultaneous liver‐kidney transplantation (SLK) in this patient population has been observed in the United States (Fig. 1).7

Figure 1.

Rising utilization of SLK in the United States.

Reason for Implementation

Historically, Organ Procurement and Transplantation Network (OPTN) policy has prioritized multiorgan candidates over kidney‐alone recipients, including highly sensitized patients (with panel‐reactive antibody >98%), pediatric patients, and patients with long waitlist times. As a consequence, kidney grafts of the highest expected longevity are frequently diverted from high‐priority kidney transplant–alone candidates to multiorgan candidates (Fig. 2), for whom strict criteria for SLK remain undefined.8 Kidney allografts with the lowest risk for graft failure are defined by a low kidney donor profile index (KDPI) less than 35%, a numerical measure of graft quality derived from a validated risk index of donor demographic and clinical parameters.9 The goal of the revised OPTN policy therefore serves to establish eligibility guidelines for SLK for more equitable allocation of renal allografts. The OPTN board ratified this policy in June 2016, and its programmatic adoption is currently being implemented.

Figure 2.

Proportion of allocated kidneys by KDPI strata for those (A) within and (B) outside the criteria of need for pretransplant dialysis and/or creatinine (Cr) concentration greater than 2.5 mg/dL at the time of transplantation.

Revised OPTN Policy for Simultaneous Liver‐Kidney Allocation

The revised allocation policy both defines medical eligibility criteria for SLK and provides a safety‐net mechanism in assigning priority for renal allograft allocation to liver transplant–alone recipients with end‐stage renal disease within 1 year of hepatic implantation.8, 10

Eligibility for SLK includes patients with hepatic failure and one of the following: (1) chronic kidney disease, (2) sustained acute kidney injury, or (3) metabolic disease. Chronic kidney disease is defined as an estimated glomerular filtration rate (eGFR) less than 60 mL/min for more than 90 days before listing, as well as an eGFR <35mL/min at the time of listing. This definition is based on United Network for Organ Sharing data, which demonstrate that patients with a pretransplant dialysis time of longer than 2 months or serum creatinine greater than 2.5 mg/dL who received an SLK transplant had a significantly improved survival at 1 and 5 years (86.2% and 70.1%, respectively) compared with those patients receiving liver transplant alone (81.1% and 65.9%).8 Sustained acute kidney injury is defined as requirement for hemodialysis and an eGFR less than 25 mL/min for 6 consecutive weeks. The definition of sustained acute kidney injury is predicated on both the low likelihood for renal recovery beyond this time and the significant mortality of this patient population.11, 12 SLK eligibility for metabolic diseases (including hyperoxaluria, atypical HUS, familial nonneuropathic systemic amyloidosis, and methylmalonic aciduria) remain unchanged from existing practice.10

The safety‐net policy recognizes that a small population of patients receiving a liver transplant alone with concurrent renal insufficiency may remain on dialysis and suffer inferior outcomes without a renal allograft. Any liver transplant recipient registered on the kidney waiting list between 60 and 365 days after liver implantation on chronic hemodialysis or with an eGFR ≤20 mL/min qualifies for increased priority until the patient receives a kidney transplant (Table 1). Because United Network for Organ Sharing data demonstrate that prior liver transplant recipients who receive a kidney transplant within 3 years have comparable survival with kidney‐alone recipients, institution of this policy enhances equitability of renal allografts between prioritized kidney‐alone candidates and liver recipients who do not recover renal function.8

Table 1.

New Allocation Sequence for Kidney Transplantation Demonstrating Safety Net for Liver Transplant Recipients With Persistent Renal Insufficiency

KDPI < 20%	KDPI = 20%‐35%	KDPI = 35%‐85%	KDPI > 85%
Highly sensitized	Highly sensitized	Highly sensitized	Highly sensitized
No HLA mismatch	No HLA mismatch	No HLA mismatch	No HLA mismatch
Prior living donor	Prior living donor	Prior living donor	Local safety net*
Local pediatrics	Local pediatrics	Local safety net*	Local + regional
Local top 20%	Local safety net*	Local	National
Estimated posttransplant survival	Local adults	Regional
No HLA mismatch (all)	Regional pediatrics	National
Local (all)	Regional adults
Regional pediatrics	National pediatrics
Regional top 20%	National adults
Regional (all)
National pediatrics
National (top 20%)
National (all)

Abbreviation: HLA, human leukocyte antigen.

Criticisms of Policy

The revised allocation policy for SLK defines strict criteria for eligibility and promotes the notion that, in an era of limited grafts, distribution of kidneys is appropriately prioritized among patients who demonstrate the greatest need. Although these changes have been welcomed by many, some have raised concerns that defined eligibility criteria may be too inclusive because some patients with acute kidney injury with eGFR less than 35 mL/min may recover renal function posttransplant.13 It is important to recognize that the criteria set forth in this allocation policy are meant to define the patient population in which SLK may be considered, rather than mandated. Others believe that the liver recipients should not be given advantage of a safety net and subject to the wait times of kidney‐alone transplant patients (Fig. 3). However, authors of the adopted proposal feel that those who suffer from end‐stage kidney disease after liver transplantation should be afforded timely access to kidney transplantation, based on the aforementioned outcome data. Furthermore, with broader sharing proposals moving forward with liver allocation, there is concern that more low‐KDPI kidneys go out to a broader sharing area with liver allocation, which is currently being modeled. Although the decision for SLK is best examined on a case‐by‐case basis, the criteria set forth in this revised policy work toward development of a transparent, equitable, evidence‐based allocation system based on demonstrable medical need and urgency.

Figure 3.

Competing risk analysis of 25th percentile of time to deceased donor kidney transplant alone for waitlisted patients 2003‐2006 with and without a prior liver transplant.