Shining a Light on the Murky Problem of Discarded Kidneys

Hall, Isaac E. MD, MS; Reese, Peter P. MD, MSCE

doi: 10.1097/TP.0000000000001558

Given the current global organ shortage, the rate of discarded organs is too high in most countries. Explaining this excessive rate is a very important and complex issue, since objective criteria of choice are often clouded by more subjective but ill-defined behaviors.

1 Division of Nephrology and Hypertension, Department of Internal Medicine, University of Utah School of Medicine, Salt Lake City, UT.

2 Renal Electrolyte and Hypertension Division, Department of Medicine, University of Pennsylvania, Philadelphia, PA.

3 Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.

The authors declare no funding or conflicts of interest.

I.H. and P.R. contributed equally to the drafting of the manuscript.

Correspondence: Peter P. Reese, MD, MSCE, 917 Blockley Hall (CCEB), 423 Guardian Drive, Philadelphia, PA 19104. (

Article Outline

Few issues in kidney transplantation generate as much controversy as organ discards. Considering that 99333 patients are waiting for a kidney transplant, the discard of nearly one fifth of the kidneys procured from deceased donors each year in the United States (approximately 2500 kidneys) is a murky problem that deserves illumination and transparency. Analyses that rely primarily on registry data and the Kidney Donor Risk Index (KDRI) suggest that some discarded kidneys are viable.1,2 Three main issues probably explain the loss of these organs: (a) problems with kidney quality are not reflected fully in the KDRI, (b) clinicians focus on posttransplant outcomes rather than maximizing access to transplant, and/or (c) there is a knowledge deficit about how good some discarded kidneys truly are. In this issue of Transplantation, Stewart et al3 assert that worsening donor characteristics account for most of the rise in discard rates over time. Although these data are important, a number of challenges remain, including how to better characterize kidney quality, and how to optimally deploy procurement kidney biopsy and hypothermic machine perfusion (HMP).

Stewart et al show that the discard rate increased steadily from about 5% in 1987 to 13% in 1999 and then plateaued around 19% since 2009. Using multivariable regression and propensity-matched analyses, they found at least 80% of the rise in discards between 1999 and 2009 could be explained by changing donor attributes as organ procurement organizations attempted to expand the donor pool. For example, donor body mass index and the proportion of donors with cardiac death rose over time. Median donor age increased to 43 years by 2009, but then returned to the 1999 level of 39 years of age by 2015. We suspect the worsening opioid epidemic (which has been devastating in the 25- to 44-year age group) is at least partially to blame for recent decreases in donor age.4 Two other factors increased steadily between 1999 and 2009 but have since stabilized—kidney biopsy (which rose from 23% to now 50% of procured kidneys) and HMP (which rose from 9% to roughly 33%). However, the study's principal finding is that up to 20% of the rise in discards (or an absolute increase of about 1%) remains unexplained by changes in donor characteristics. The authors discuss the possibility that transplant programs are excessively focused on protecting their posttransplant outcomes, but their analyses may also support the idea that transplant teams need education about the true quality of many discarded organs.

Although these analyses shed new light on the complex topic of organ utilization, it is important to carefully consider the limitations of registry data. No adjustments were made for Public Health Service infectious-risk kidneys, which carry the stigma of HIV risk but should have minimal impact on decision-making for clinicians or patients totally focused on improving survival.5 There were no adjustments for donor infections, renal anatomy (eg, torn or severely atherosclerotic vessels), or the hemodynamic course for donors with cardiac death (eg, unfavorable warm ischemia time). Inefficient allocation processes were not addressed (eg, high KDRI kidneys offered serially to multiple centers that only accept lower-risk organs, leading to prolonged cold ischemia); such problems may have worsened in the new kidney allocation system. Importantly, if these other factors could be accurately measured and shown to be meaningful, they would provide evidence for explanation “a” above (KDRI limitations), and policy committees could push for better data collection in these areas.

Although most factors that influence discard are probably intrinsic to the allograft (eg, age), medical judgment determines whether biopsies or HMP are performed. The problem with studying these factors is called “confounding-by-indication.” For example, the authors face the problem that it is difficult to decipher whether valid suspicions about allograft quality lead to kidney biopsies versus whether biopsies generate little useful information and drive bogus concerns about quality. Stewart et al suspect the latter explanation. Had the proportion of biopsies remained unchanged between 1999 and 2009, they contend that the discard rate would have likely remained stable or even decreased. Given concerns about variability in procurement biopsy quality and interpretation,6,7 there is an urgent need to standardize the process and develop trials to determine the optimal role for this controversial procedure. In contrast, the more common use of HMP appears to have prevented an even greater number of kidney discards. Yet, we believe that determining the optimal approach to using HMP, not to mention newer perfusion techniques in development, requires additional clinical trials and protocol standardization.

Changes to payments, policy, practice, or regulations could also reduce organ discards.8 Transplant programs are reimbursed at the same rate regardless of the risk of posttransplant complications and then face penalties for worse-than-expected outcomes. Financial rewards to promote acceptance of lower-quality organs might well change organ decision making.9,10 However, persuading payers to develop new approaches to reimbursing for transplant may be difficult. Although not directly tied to reimbursement, the Organ Procurement and Transplantation Network Collaborative Innovation and Improvement Network project will evaluate alternative approaches to monitoring transplant programs and appears to be a reasonable start from a regulatory perspective. Additional considerations could include enhanced decision support for transplant teams during organ allocation and more constructive feedback about organs they declined that were successfully transplanted elsewhere. Lastly, it makes sense to reward centers that do consistently take high-risk organs by allowing them rapid access to high-risk organ offers in the future.

We also need research to improve risk adjustment and better characterize allograft quality. Models in current clinical/regulatory use are based on kidneys accepted in the past. Researchers, institutional review boards, and study participants will need to consider the potential risks of accepting kidneys that are commonly rejected—risks that are difficult to estimate until reasonable numbers of such transplants and outcomes are reported. A thorough informed consent process—that is revisited at subsequent pretransplant evaluations regarding probability of health deterioration on the waiting list versus the probability of an adverse transplant outcome11—could also improve risk tolerance for higher-risk organs. In addition, national investments in precision medicine may yield novel tools, perhaps from genomics or proteomics, to improve individualized predictions about allograft function and survival for high-risk kidney transplants.

In conclusion, these insightful analyses from Stewart and colleagues reveal that efforts to expand the donor pool probably also led to a rise in discards of procured kidneys. The next challenge is using these data to light the way toward effective policy, trials, and strategies to change behavior.

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