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Swaps and Chains and Vouchers, Oh My!: Evaluating How Saving More Lives Impacts the Equitable Allocation of Live Donor Kidneys

Published online by Cambridge University Press:  06 January 2021

Evelyn M. Tenenbaum
Evelyn M. Tenenbaum*
Affiliation:
Albany Law School and Professor of Bioethics, Albany Medical College
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Abstract

Live kidney donation involves a delicate balance between saving the most lives possible and maintaining a transplant system that is fair to the many thousands of patients on the transplant waiting list. Federal law and regulations require that kidney allocation be equitable, but the pressure to save patients subject to ever-lengthening waiting times for a transplant has been swinging the balance toward optimizing utility at the expense of justice.

This article traces the progression of innovations created to make optimum use of a patient's own live donors. It starts with the simplest – direct donation by family members – and ends with voucher donations, a very recent and unique innovation because the donor can donate 20 or more years before the intended recipient is expected to need a kidney. In return for the donation, the intended recipient receives a voucher that can be redeemed for a live kidney when it is needed. Other innovations that are discussed include kidney exchanges and list paired donation, which are used to facilitate donor swaps when donor/recipient pairs have incompatible blood types.

The discussion of each new innovation shows how the equity issues build on each other and how, with each new innovation, it becomes progressively harder to find an acceptable balance between utility and justice. The article culminates with an analysis of two recent allocation methods that have the potential to save many additional lives, but also affirmatively harm some patients on the deceased donor waiting list by increasing their waiting time for a life-saving kidney. The article concludes that saving additional lives does not justify harming patients on the waiting list unless that harm can be minimized. It also proposes solutions to minimize the harm so these new innovations can equitably perform their intended function of stimulating additional transplants and extending the lives of many transplant patients.

Type
Articles
Information
American Journal of Law & Medicine , Volume 44 , Issue 1 , March 2018 , pp. 67 - 118
Copyright
Copyright © American Society of Law, Medicine and Ethics and Boston University 2018

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References

1 Jeffrey Veale, Opinion, Give a Kidney, Get a Kidney, Wall St. J. (Aug. 3, 2016, 7:06 PM), https://www.wsj.com/articles/give-a-kidney-get-a-kidney-1470265583.

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5 See Living Donors, Nat'l Kidney Registry, http://kidneyregistry.org/living_donors.php [https://perma.cc/Q8LR-WNX5].

6 Kerstein, supra note 2, at 561 (noting that dialysis “tends to yield worse health outcomes than transplantation”); Dan Davis & Rebecca Wolitz, The Ethics of Organ Allocation (Sept. 2006) (unpublished working paper) (on file with author) (https://bioethicsarchive.georgetown.edu/pcbe/background/davispaper.html) [https://perma.cc/T6ZU-2EGT].

7 Living Donors, supra note 5.

8 See Wallis, C. Bradley et al., Kidney Paired Donation, 26 Nephrology Dialysis Transplantation 2091, 2091 (2011)CrossRefGoogle ScholarPubMed (“Patients fortunate enough to receive a kidney transplant, on average, live 10 years longer than those who remain on dialysis….”); see also Organ Donation and Transplantation Statistics, supra note 3.

9 Organ Donation and Transplantation Statistics, supra note 3 (“In 2014, 4,761 patients died while waiting for a kidney transplant. Another … 3,668 people became too sick to receive a kidney transplant.”).

10 See Kulkarni, Sanjay & Cronin, David C. II, Ethical Tensions in Solid Organ Transplantation: The Price of Success, 12 World J. Gastroenterology 3259, 3260 (2006)CrossRefGoogle Scholar (“One of the major ways transplant centers have attempted to increase the number of transplants performed is through increasing the numbers of living donors.”).

11 See Wallis et al., supra note 8, at 2091 (“[I]t is now clear that a living donor kidney transplant is better than a kidney from a deceased donor.”).

12 Martin, Dominique E. & Danovitch, Gabriel M., Banking on Living Kidney Donors – A New Way to Facilitate Donation Without Compromising on Ethical Values, 42 J. Med. & Phil. 537, 538 (2017).CrossRefGoogle ScholarPubMed

13 Veale, supra note 1.

14 See, e.g., Mark E. Neumann, Transplant Community Looks for Ways to Increase Living Kidney Donation, Nephology News & Issues (Jan. 28, 2016), https://www.nephrologynews.com/transplant-community-looks-for-ways-to-incentivize-living-kidney-donation/ [https://perma.cc/88TE-VBLW]; see also Martin & Danovitch, supra note 12, at 538 (“Recent efforts to increase living donation have … address[ed] barriers [to donation] such as the financial costs or disincentives associated with donation, lack of awareness and education about donation opportunities, and immunological incompatibilities.”) (internal citations omitted).

15 See infra Part III.

16 See infra Part IV.

17 See infra Part V.

18 See infra Part VI.

19 See infra Part VII.

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21 See Ghods, supra note 20, at 187.

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23 See infra Parts III, IV.

24 See infra Parts III, IV.

25 See infra Parts V, VI, VII.

26 See infra Parts VI, VII.

27 See Olbrisch, Mary Ellen et al., Psychosocial Assessment of Living Organ Donors: Clinical and Ethical Considerations, 11 Progress Transplantation 40, 45 (2001)CrossRefGoogle ScholarPubMed (“As the ratio of demand to supply continues to increase, there will be more living donors, more requests for persons to become living donors, and more ethical concerns with which to contend.”).

28 See National Organ Transplant Act of 1986, 42 U.S.C. §§ 274(a)-(b)(1)(A) (2013) (“The Secretary [of HHS] shall … contract … for the establishment and operation of an Organ Procurement and Transplantation Network [with] a private nonprofit entity that has an expertise in organ procurement and transplantation….”); Ayres, Ian et al., Unequal Racial Access to Kidney Transplantation, 46 Vand. L. Rev. 805, 813-14 (1993)Google ScholarPubMed; Morley, Michael T., Increasing the Supply of Organs for Transplantation Through Paired Organ Exchanges, 21 Yale L. & Pol'y Rev. 221, 234-35 (2003).Google Scholar

29 See 42 U.S.C. §§ 274(b)(2)(A)(i)-(ii) (2013); see also Glazier, Alexandra K. & Sasjack, Scott, Should It Be Illicit to Solicit? A Legal Analysis of Policy Options to Regulate Solicitation of Organs for Transplant, 17 Health Matrix 63, 88 (2007)Google ScholarPubMed (“In 1984, Congress authorized the [OPTN] to set national organ allocation policies….”).

30 See 42 U.S.C. § 273(b)(3)(E) (2013)(“An organ procurement organization shall … have a system to allocate donated organs equitably among transplant patients according to established medical criteria….”); Organ Procurement and Transplantation Network, 42 C.F.R. § 121.8(b) (2016) (“Allocation policies shall be designed to achieve equitable allocation of organs among patients….”); see also Rees, Michael A. et al., A Nonsimultaneous, Extended, Altruistic-Donor Chain, 360 New Eng. J. Med. 1096, 1099 (2009)CrossRefGoogle ScholarPubMed (“[T]he National Organ Transplant Act … calls for the development of ‘a system to allocate donated organs equitably among transplant patients, according to established medical criteria.’”); see also Davis & Wolitz, supra note 6 (“[T]he Code of Federal Regulations[] charges OPTN with the task of developing ‘policies for the equitable allocation of cadaveric organs….’”).

31 See Roth, Alvin E. et al., Kidney Exchange, 119 Q.J. Econ. 457, 461 (2004)CrossRefGoogle Scholar (“When a cadaveric kidney becomes available for transplantation, the priority of each patient on the waiting list is determined by a point system….”).

32 Rees et al., supra note 30, at 1099 (“The United Network for Organ Sharing … has interpreted equitable to mean ‘balanced between justice and utility.’”); Smith, J.M. et al., Kidney, Pancreas and Liver Allocation and Distribution in the United States, 12 Am. J. Transplantation 3191, 3192 (2012)CrossRefGoogle ScholarPubMed (“The goal of deceased donor organ allocation policy in the US has been to balance utility and equity in the distribution of deceased donor organs.”); Wallis et al., supra note 8, at 2094 (“The United Network for Organ Sharing … defines ‘equitable’ as a balance between utility and justice.”).

33 See Davis & Wolitz, supra note 6 (noting that the ethical principles of utility and equity “govern the allocation system….”).

34 42 C.F.R. § 121.8(a)(2) (2016).

35 Id. § 121.8(a)(5).

36 Id. § 121.8(a)(1); Davis & Wolitz, supra note 6.

37 See Wall et al., supra note 22, at 2820 (“The principle of utility states that an action is right if it promotes as much or more good than an alternative action.”); see also Davis & Wolitz, supra note 6.

38 Wall et al., supra note 22, at 2820 (“[A]ggregate good can be measured in graft survival, patient survival, or quality adjusted life years, among other criteria.”).

39 See IV.13 Analysis of Patient and Graft Survival, 17 Nephrology Dialysis Transplantation 60, 60 (Supp. 4 2002).CrossRefGoogle Scholar

40 See Ceri Phillips & Guy Thompson, What is a QALY?, Hayward Med. Comm., at 1 (2001) (“A quality-adjusted life year (QALY) takes into account both quantity and the quality of life generated by healthcare interventions. It is the arithmetic product of life expectancy and a measure of the quality of the remaining life years.”).

41 See Glazier & Sasjack, supra note 29, at 66 (“[T]he allocation process is designed to accomplish utility by using clinical factors to distribute organs to recipients who are expected to realize the greatest clinical benefit in terms of expected survival (or collectively ‘net benefit’).”); Wall et al., supra note 22, at 2820 (“Prioritization of outcomes favors patients expected to have better quality of life, quantity of life, or longevity of graft survival.”); see also Ethical Principles in the Allocation of Human Organs, Organ Procurement and Transplantation Network (June 2015), https://optn.transplant.hrsa.gov/resources/ethics/ethical-principles-in-the-allocation-of-human-organs/ [https://perma.cc/9RDZ-RTHZ] (“[F]actors to be considered in the application of the principle of utility are: 1) patient survival; 2) graft survival; 3) quality of life; 4) availability of alternative treatments; and 5) age.”).

42 See Smith et al., supra note 32, at 3193 (“[A]llocation policy for deceased donor kidneys gives priority to candidates with zero antigen mismatch….”).

43 See Gaston, Robert S., Addressing Minority Issues in Renal Transplantation: Is More Equitable Access an Achievable Goal?, 2 Am. J. Transplantation 1, 2 (2002).CrossRefGoogle ScholarPubMed

44 See Morley, supra note 28, at 229, 232 (noting that when blood type and all six antigens match, there are “high transplantation success rates without adverse side effects….”).

45 See Robert M. Veatch & Lainie F. Ross, Transplantation Ethics 292 (2d ed. 2015) (“[T]he focus of any theory of justice is not on the amount of good done but on the pattern of the distribution of the good.”).

46 See Davis & Wolitz, supra note 6.

47 See id. (“[T]he health of those on dialysis tends to degenerate over an extended period of time. Many patients are less healthy by the time they receive a kidney transplant, while others die waiting….”).

48 See Robert M. Veatch, Transplantation Ethics, 291, 295 (1st ed. 2000) (“[Utilitarians] would discriminate against any hard to treat group [and] some people are so ill … they will predictably not get as much benefit from a transplant as some who are healthier.”).

49 See Glazier & Sasjack, supra note 29, at 66 (“Preferences are given according to certain equitable factors, such as time spent on the wait list and medical urgency.”); Morley, supra note 28, at 230 n.41 (“Extra points are awarded based on the length of time the patient has been on the waiting list.”).

50 Wall et al., supra note 22, at 2820.

51 See Morley, supra note 28, at 230 n.41 (“Patients for whom it is especially difficult to find histocompatible organs receive extra points.”).

52 See Keith & Vranic, supra note 4, at 684, 691 (“[F]or patients seeking transplant who are highly sensitized, wait times have traditionally been long and options limited … For the recipient with a very high cPRA, such as 99.99%, the probability of finding a donor in a realistic time frame is extraordinarily low….”).

53 See Veatch, supra note 48, at 338 (“[E]ven if it is more efficient to give the organs to younger persons, doing so is unfair.”).

54 See Davis & Wolitz, supra note 6 (citing Childress, James F., Putting Patients First in Organ Allocation: An Ethical Analysis of the U.S. Debate, 10 Cambridge Q. Healthcare Ethics 365, 366 (2001)CrossRefGoogle ScholarPubMed (“[D]istrust is a major reason for the public's reluctance to donate organs, and policies of organ procurement may be ineffective if the public perceives the policies of organ allocation as unfair and thus untrustworthy.”)).

55 See Israni, Ajay K. et al., Incentive Models to Increase Living Kidney Donation: Encouraging Without Coercing, 5 Am. J. Transplantation 15, 15 (2005)CrossRefGoogle ScholarPubMed (“Affluent patients seeking kidney donations can now circumvent the long waiting list by buying their kidneys from brokers who locate overseas ‘vendors’ willing to sell their kidneys.”).

56 See id. at 16 (“‘[U]nder the table’ financial exchanges are an increasing presence in donations from friends and family.”); Jennifer Monti, The Case for Compensating Live Organ Donors, Competitive Enterprise Inst., Apr. 2009, at 5 (noting “the development of a thriving black market for procurement of organs from live donors [in the United States].”); Tammy Leitner & Lisa Capitanini, Market for Black Market Organs Expands, NBC Chi. (May 19, 2014, 10:50 PM), http://www.nbcchicago.com/investigations/Market-For-Black-Market-Organs-Expands-259889741.html [https://perma.cc/3MPF-H9HE].

57 See Olbrisch et al., supra note 27, at 42, 44 (“[I]ndividuals might conceal important information about their health histories and risk behaviors to make an anticipated sale … includ[ing] concealment of medical or psychiatric history.”).

58 See id. at 44 (“Minimization of alcohol and other drug abuse may occur….”).

59 See Rosen, Lara et al., Addessing the Shortage of Kidneys for Transplantation: Purchase and Allocation Through Chain Auctions, 36 J. Health Pols., Pol'y & L. 717, 730-31 (2011)CrossRefGoogle Scholar (“The OPTN did not initially have responsibility for overseeing live donations … In 2004, the Department of Health and Human Services directed the OPTN to develop data reporting requirements and guidelines for live donation.”).

60 Id. at 731.

61 See, e.g., Organ Procurement & Transplantation Network, Policies §§ 8.3, 14 (2017) (requiring specific allocation procedures for deceased donor kidneys but allowing institutions to create their own allocation procedures for living donor kidneys).

62 See generally Nat'l Kidney Registry, http://www.kidneyregistry.org (last visited Aug. 16, 2017) (containing information about their own guidelines for distribution to increase the number of living donations).

63 See Rosen et al., supra note 59, at 728 (“The most common type of live donation occurs when a family member or friend of a patient donates an organ.”); see also Allen, M.B. et al., What Are the Harms of Refusing to Allow Living Kidney Donation? An Expanded View of Risks and Benefits, 14 Am. J. Transplantation 531, 531 (2014)CrossRefGoogle ScholarPubMed (“Over 5500 living kidney donor transplants take place each year in the United States, and directed donation by spouses and close family members accounts for 87% of living kidney transplants since 1988.”).

64 See Joshua J. Augustine et al., Kidney and Pancreas Transplantation, in Primer on Transplantation 129, 129 (Donald Hricik ed., 3d ed. 2011) (“[T]he first successful kidney transplantation [was] performed between identical twin brothers by Dr. Joseph Murray and colleagues at the Peter Bent Brigham Hospital in Boston.”); Williams, Kristy Lynn et al., Just Say No to NOTA: Why the Prohibition of Compensation for Human Transplant Organs in NOTA Should Be Repealed and a Regulated Market for Cadaver Organs Instituted, 40 Am. J.L. & Med. 275, 278–79 (2014)Google Scholar (“The first long-term successful kidney transplant occurred in 1954, when a kidney was transplanted from a healthy twin to his brother who was suffering from advanced kidney disease.”).

65 See Organ Procurement & Transplantation Network, 42 C.F.R. § 121.8(h) (2016) (“Nothing in this section shall prohibit the allocation of an organ to a recipient named by those authorized to make the donation.”).

66 See Glazier & Sasjack, supra note 29, at 65-66 n.15 (“Federal regulations promulgated by the Department of Health and Human Services (HHS) expressly permit directed donations.”); see also, e.g., Cal. Health & Safety Code § 7150.50(a) (West 2017) (“An anatomical gift may be made to … an individual designated by the person making the anatomical gift if the individual is the recipient of the part.”); N.Y. Pub. Health Law § 4303(3) (McKinney 2017); Tex. Health & Safety Code Ann. § 692A.011(a)(3) (West 2017); Vt. Stat. Ann. tit. 18, § 5250k(a)(2) (West 2017).

67 Allen et al., supra note 63, at 531 (“Over 5500 living kidney donor transplants take place each year in the United States, and directed donation by spouses and close family members accounts for 87% of living kidney transplants since 1988.”).

68 See Davis & Wolitz, supra note 6 (“[L]iving donors … usually [donate to] a family member or friend. The recipient thus receives an organ based not upon her level of medical need or urgency compared to other potential recipients, but because … the potential donor … willingly gives up an organ to help or save (only) the ailing person he loves.”).

69 See Glazier & Sasjack, supra note 29, at 68.

70 See Davis & Wolitz, supra note 6 (citing Burdick, James, Responses to ‘A Critique of UNOS Liver Allocation Policy’ by Kenneth Einar Himma, 9 Cambridge Q. Healthcare Ethics 275, 275 (2000)CrossRefGoogle Scholar (“[B]ecause there are not enough donated organs, all patients and practitioners are bound together by a community of medicine principle: whenever a patient receives a transplant, it diminishes the chance that other potential recipients will be able to receive this gift of life in time to save them.”)).

71 See Glazier & Sasjack, supra note 29, at 64 (“[D]irected donations to strangers are uncommon.”); Morley, supra note 28, at 254 (“[P]rohibiting directed donation would be disastrous for organ procurement from living donors [because] [v]ery few living donors give their organs to strangers.”); Davis & Wolitz, supra note 6 (“Most living donors donate to someone in particular–usually a family member or friend.”).

72 See Glazier & Sasjack, supra note 29, at 73 (“Increasing the total number of living organ donations is more likely to benefit other potential recipients rather than to deprive them of organs that they otherwise might have received.”).

73 See id. at 66-67 (noting that increasing total live donations benefits everyone on the waiting list by removing those who successfully receive a kidney).

74 See id. at 73 (“[L]iving donors are more likely to increase total organ donations in a manner that remains fair in the balance.”).

75 See Ghods, supra note 20, at 188; see also Olbrisch et al., supra note 27, at 46.

76 See Kallich, Joel D. & Merz, Jon F., The Transplant Imperative: Protecting Living Donors from the Pressure to Donate, 20 J. Corp. L. 139, 151 (1994)Google ScholarPubMed (“Ethicists have justified the imposition of risk on one person on the grounds of reducing the risk to another, believing that society is better off.”).

77 Veale, supra note 1 (“[For donors t]here is a 3 in 10,000 death rate and approximately a 5 in 1,000 chance that donors will develop end-stage renal disease.”).

78 See Lobas, Kelly, Living Organ Donations: How Can Society Ethically Increase the Supply of Organs?, 30 Seton Hall Legis. J. 475, 488-89 (2006)Google Scholar (“[R]isks include ‘side effects associated with allergic reactions to the anesthesia, pneumonia, blood clots, hemorrhaging, the need for blood transfusions [and] infection of the wound or urinary tract….’”).

79 See id. at 489 (“[O]ccurrences of short-term risks are ‘very low.’”); Ramcharan, Thiagarajan & Matas, Arthur J., Long-Term (20-37 Years) Follow-Up of Living Kidney Donors, 2 Am. J. Transplantation 959, 959 (2002)CrossRefGoogle ScholarPubMed (“Perioperative mortality after living kidney donation has been estimated to be 0.03%; morbidity, including minor complications, < 10%.”).

80 See Gaston, Robert S. et al., Reassessing Medical Risk in Living Kidney Donors, 26 J. Am. Soc'y Nephrology 1017, 1018 (2015).CrossRefGoogle ScholarPubMed

81 Id. at 1018.

82 See id. (“[T]hese data [are] a work in progress…. [and] additional studies must and will be performed, with findings that will further refine our understanding of long-term donor risk and expand the evidence base necessary to support informed policymaking.”); see also Gentry, Sommer E. et al., Kidney Paired Donation: Fundamentals, Limitations, and Expansions, 57 Am. J. Kidney Diseases 144, 148 (2011)CrossRefGoogle ScholarPubMed [hereinafter Gentry et al. 2011] (“[R]esearch has suggested that living kidney donors do not have an increased risk of [ESRD] or hypertension.”); Mjøen, Geir et al., Long-Term Risks for Kidney Donors, 86 Kidney Int'l 162, 162 (2014)CrossRefGoogle ScholarPubMed (“Follow-up studies of living organ donors have not reported increased cardiovascular and all-cause mortality, but [there may be a significant increase in ESRD, cardiovascular, and all-cause mortality in the long-term and recommending that further studies be performed].”).

83 Wallis et al., supra note 8, at 2091.

84 Guedes, Anabela Malho et al., Over Ten-Year Kidney Graft Survival Determinants, 2012 Int'l J. Nephrology 1, 3 (2012)Google ScholarPubMed (“The half-life for deceased and living related allografts have improved to 13.8 and 21.6 years, respectively.”).

85 Kevin Sack, 60 Lives, 30 Kidneys, All Linked, N.Y. Times (Feb. 18, 2012), http://www.nytimes.com/2012/02/19/health/lives-forever-linked-through-kidney-transplant-chain-124.html (noting that dialysis requires patients to tether themselves to dialysis machines for approximately four hours, three times a week and that dialysis “saps the productivity of caregivers as well as of patients.”); see also Rosen et al., supra note 59, at 718 (describing dialysis as “physically and emotionally debilitating….”).

86 See 153 Cong. Rec. 5,437 (2007) (statement of Rep. Norwood) (“While dialysis extends patients' lives, their condition often prevents them from being fully engaged in their community and career. Dialysis is life-extending, but not life-bettering.”); Rosen et al., supra note 59, at 717 (“[T]ransplantation offer[s] improved quality of life and increased longevity relative to dialysis….”).

87 See Adams, Patricia L. et al., The Nondirected Live-Kidney Donor: Ethical Considerations and Practice Guidelines, 74 Transplantation 582, 586 (2002)CrossRefGoogle ScholarPubMed (“[The] donor is usually rewarded because a loved one or friend has enjoyed improved health and quality of life from the donation.”); Glannon, Walter & Ross, Lainie Friedman, Do Genetic Relationships Create Moral Obligations in Organ Transplantation?, 11 Cambridge Q. Healthcare Ethics 153, 153-54 (2002)CrossRefGoogle ScholarPubMed (“[A] person can derive a psychological benefit from saving a life by donating an organ.”).

88 Olbrisch et al., supra note 27, at 46.

89 See Allen et al., supra note 63, at 533.

90 See Adams et al., supra note 87, at 586 (“[The] donor is usually rewarded because a loved one or friend has enjoyed improved health and quality of life from the donation.”); Allen et al., supra note 63, at 533 (explaining how lack of donation can cause financial and caregivier burdens); Gaston et al., supra note 80, at 1018 (citing study showing healthy donors have a slightly increased risk of kidney disease); Glannon & Ross, supra note 87, at 154.

91 See Glazier & Sasjack, supra note 29, at 66-67 (noting that increasing total live donations benefits everyone by decreasing the number of persons on the waiting list for deceased organs).

92 See id. at 71, 73 (explaining how directed live donation reduces competition by taking patients off the waiting list for deceased organs).

93 See Susan V. Fuggle & Craig J. Taylor, Histocompatibility in Kidney Transplantation, in Kidney Transplantation: Principles and Practice 142, 142 (Peter J. Morris & Stuart J. Knechtle eds., 7th ed. 2014) (“[Before immunosuppressants,] 40-50% of deceased donor transplants were lost from immediate or early graft failure due to irreversible rejection in the first year and thereafter there was an insidious decline in graft function.”); Dicken S.C. Ko & Francis L. Delmonico, Medical Evaluation of the Living Donor, in Kidney Transplantation: Principles and Practice 99, 99 (Peter J. Morris & Stuart J. Knechtle eds., 6th ed. 2008) (“[M]any dialysis patients were hesitant to consider transplantation unless a related donor was available.”).

94 Cyclosporine, Merriam-Webster, https://www.merriam-webster.com/dictionary/cyclosporine [https://perma.cc/JQE8-Q52Z].

95 Ayres et al., supra note 28, at 852 (“The introduction of cyclosporine in 1984 revolutionized transplantation, markedly improving results in renal transplantation….”).

96 See Dew, M.A. et al., Guidelines for the Psychosocial Evaluation of Living Unrelated Kidney Donors in the United States, 7 Am. J. Transplantation 1047, 1047 (2007)CrossRefGoogle Scholar (“Transplant candidates may [solicit] via the Internet, print media or word of mouth.”); Truog, Robert D., The Ethics of Organ Donation by Living Donors, 353 New Eng. J. Med. 444, 445 (2005)CrossRefGoogle ScholarPubMed (“Directed donation to a stranger … usually occurs when a patient advertises for an organ publicly, on television or billboards or over the Internet.”).

97 See Davis & Wolitz, supra note 6 (“[O]rgan donations … to unrelated strangers … have been subject to moral suspicion and critique, especially when donations to unrelated strangers have followed public solicitation campaigns.”).

98 See Glazier & Sasjack, supra note 29, at 70 (“Organ solicitations could undermine public support … because [they] inequitably favor[] those patients with ‘attractiveness’ and the means to purchase advertising or draw media attention.”).

99 See Truog, supra note 96, at 445 (“[With] directed donation to strangers … it will be very difficult to prohibit discriminatory preferences, since donors can simply specify that the organ must go to a particular person, without saying why.”).

100 See Eike-Henner W. Kluge, Designated Organ Donation: Private Choice in Social Context, Hastings Ctr. Rep., Sept.-Oct. 1989, at 12 (“Photogenic appeal [and] having private funds available for a media campaign … could not be considered appropriate criteria [for organ allocation].”); Arthur Caplan, Commentary, Cutting in Line for Organ Transplants: Texas Man's Efforts to Get Liver Undermine System, NBC News (Aug. 25, 2004), http://www.nbcnews.com/id/5810779/ns/health-health_care/t/cutting-line-organ-transplants/#.WYm4EYgrK00 [https://perma.cc/44SH-3PTK] (“[T]he whole point of the organ distribution system, which has been in place since 1986, is to give everyone in need of a transplant—not just those who can pay for ads and grab national media attention—an equal shot.”).

101 See Kluge, supra note 100, at 14 (“[Soliciting organs is] unethical because someone who according to equity and justice was entitled to the organ is deprived of it.”).

102 See id. at 12 (“Family ties … are uniquely privileging … and designated organ donation occurring within the immediate family context does not violate the equality-and-justice condition.”).

103 See Morley, supra note 28, at 253 (“Others have maintained that once a donor ‘has decided to give, the donation is subject to the constraints of equality and justice.’”).

104 See Davis & Wolitz, supra note 6 (“Even if directed donations generate benefits for the system overall, to the extent that these practices enable individuals to ‘cut in line,’ to use the advantages of socioeconomic status to reap the additional advantage of publicity, they should be condemned as inherently unfair.”); Glazier & Sasjack, supra note 29, at 98 (“Public solicitations … threaten to undermine the national system, which is carefully established to equitably and efficiently allocate deceased organs.”).

105 See Morley, supra note 28, at 253; see also Kluge, supra note 100, at 13 (“[If] someone who otherwise would have made an undesignated donation donates to [a] specific individual[,] … someone who is higher on the waiting list … would lose what rightfully is his or hers.”).

106 See Glazier & Sasjack, supra note 29, at 68 (“Proponents of donor solicitation believe that … solicitations will increase the total number of organ donations by persuading people who otherwise would not donate to do so.”).

107 See id. at 71-72 (“[D]ata support[] the conclusion that solicitation will likely increase living donations because living donors prefer to donate to a person they know…. [and] anonymous, non-directed donations to the waiting list … are rare.”).

108 See id. at 98 (commenting that solicitation of donors will not “compromis[e] the principles of an established allocation system”); Sherwin, Trevor et al., Is Directed Donation Misguided?, 32 Clinical & Experimental Ophthalmology 5, 6 (2004).CrossRefGoogle ScholarPubMed

109 See Lobas, supra note 78, at 501 (“[S]ome individuals are not fortunate enough to have a large family or a social community where there is a willing donor.”).

110 See Glazier & Sasjack, supra note 29, at 70 (“[D]onors of deceased organs who direct donations to solicitors are likely to have donated anyway.”).

111 See id. at 69 (“The likely outcome of continuing to allow public solicitations of deceased organs is that deceased organs that might otherwise be made available would be withheld from those patients ranked higher than the solicitor on the UNOS waiting list.”).

112 See id. at 70 (“[Those who advertise for deceased donor kidneys] may move ahead of those who have waited longer, would benefit more, or have more critical need.”).

113 See Cronin, Antonia J. & Price, David, Directed Organ Donation: Is the Donor the Owner?, 3 Clinical Ethics 127, 128 (2008)CrossRefGoogle ScholarPubMed (“[T]he dominant trend domestically and internationally is that organs from deceased donors should be distributed according to principles of justice and equity…. [The] two parallel donation/allocation regimes operate in most jurisdictions, with (in essence) an impartial justice rationale governing deceased donation and a partial autonomy-driven rationale underpinning living donation.”). Compare Human Tissue Authority, Code F: Donation of Solid Organs and Tissue for Transplantation: Code of Practice 9 (2007), https://www.hta.gov.uk/hta-codes-practice-and-standards-0 [https://perma.cc/2TUR-FAQ7] (“[In the United Kingdom, t]he law allows a living donor to request that their donation be directed to any identified individual, regardless of whether or not he or she has a relationship (genetic or otherwise) with the intended recipient. It is not an offence to advertise, either via traditional or social media, to find a suitable donor.”), with How the Organ Donor System Works, BBC News (Apr. 12, 2008, 5:06 PM), http://news.bbc.co.uk/2/mobile/uk_news/7344343.stm [https://perma.cc/8HXD-8DH3] (“Currently all deceased organ donation in the UK is non-directed: organs are allocated according to clinical need and compatibility rather than according to any specific wishes of the donor communicated while they were alive or of their family.”), and Mother Denied Daughter's Organs, BBC News (Apr. 12, 2008, 2:00 PM), http://news.bbc.co.uk/2/hi/uk_news/england/bradford/7344205.stm [https://perma.cc/N7EP-M78J] (“Adrian McNeil, chief executive of the [Human Tissue Authority], said: ‘The central principle of matching and allocating organs from the deceased is that they are allocated to the person on the UK transplant waiting list who is most in need and who is the best match with the donor.’”).

114 See Organ Procurement and Transplantation Network, 42 C.F.R. § 121.8(h) (2016) (“Nothing in this section shall prohibit the allocation of an organ to a recipient named by those authorized to make the donation.”).

115 See Lobas, supra note 78, at 488-89 (explaining the risks to the donor associated with live organ donation).

116 See, e.g., Glazier & Sasjack, supra note 29, at 65.

117 See id. at 81 n.97 (“[L]iving donors may benefit by knowing that they have saved or improved a life. Thus, it is not reasonable to presume that living donor solicitations will harm living donors more often than not….”).

118 See Morley, supra note 28, at 254 (“[A] person who undergoes the risk and inconvenience of the organ removal process solidifies his right to designate a recipient for the organ.”).

119 See Davis & Wolitz, supra note 6 (“[D]irected donation is morally permissible for living donors, who are due a measure of respect for the profoundly personal choices involved in giving the gift of life….”); Morley, supra note 28, at 254.

120 See Glazier & Sasjack, supra note 29, at 81 n.97 (“[L]iving donors may benefit by knowing that they have saved or improved a life. Thus, it is not reasonable to presume that living donor solicitations will harm living donors more often than not….”).

121 See id. at 71-72.

122 John W. McMahon, Council on Ethical and Judicial Affs., Nonsimultaneous, Altruistic Organ Donation 6 (2010), https://www.ama-assn.org/sites/default/files/media-browser/public/about-ama/councils/Council%20Reports/council-on-ethics-and-judicial-affairs/i10-cejanonsimultaneous-altruistic-organ-donation.pdf (“Designation of a stranger as the intended recipient is ethical if it produces a net gain of organs in the organ pool without unreasonably disadvantaging others on the waiting list.”).

123 Veale, Jeffrey L. et al., Vouchers for Future Kidney Transplants to Overcome “Chronological Incompatibility” Between Living Donors and Recipients, 101 Transplantation 2115, 2115 (2017)CrossRefGoogle ScholarPubMed; see Glorie, Kristiaan M. et al., Coordinating Unspecified Living Kidney Donation and Transplantation Across the Blood-Type Barrier in Kidney Exchange, 96 Transplantation 814, 814 (2013)CrossRefGoogle ScholarPubMed (“[M]ore than 30% of living [kidney] donors are incompatible with their intended recipient.”).

124 See Delmonico, Francis L. et al., Donor Kidney Exchanges, 4 Am. J. Transplantation 1628, 1633 (2004)CrossRefGoogle ScholarPubMed (“[Paired kidney donation] yield[s] an additional donor source for patients awaiting a deceased donor kidney.”).

125 See generally Tenenbaum, Evelyn M., Bartering for a Compatible Kidney Using Your Incompatible, Live Kidney Donor: Legal and Ethical Issues Related to Kidney Chains, 42 Am. J.L. & Med. 129, 145-53 (2016)CrossRefGoogle ScholarPubMed (providing background and explanations of the processes of paired kidney donation, domino paired donations, and NEAD chains).

126 See Gentry et al. 2011, supra note 82, at 146.

127 See Wallis et al., supra note 8, at 2091; Ross, Lainie Friedman et al., Ethical and Logistical Issues Raised by the Advanced Donation Program “Pay It Forward” Scheme, 42 J. Med. & Phil. 518, 519 (2017)CrossRefGoogle ScholarPubMed (noting that “the first kidney exchange in the United States was not carried out until 2000 at Rhode Island Hospital.”).

128 See Montgomery, R.A., Renal Transplantation Across HLA and ABO Antibody Barriers: Integrating Paired Donation into Desensitization Protocols, 10 Am. J. Transplantation 449, 452 (2010)CrossRefGoogle ScholarPubMed (“[Kidney paired donation] involves matching a potential kidney recipient who has a willing but incompatible donor to another incompatible pair.”).

129 See Segev, Dorry L. et al., Utilization and Outcomes of Kidney Paired Donation in the United States, 86 Transplantation 502, 502 (2008)CrossRefGoogle ScholarPubMed (“[K]idney paired donation … allows pairs of recipients and their willing but incompatible live donors to find reciprocal matches and undergo transplantation by exchanging donors.”); see also Delmonico et al., supra note 124, at 1628.

130 See Morley, supra note 28, at 227 (“For a kidney to be histocompatible with a potential recipient, only two sets of antigens must match—ABO and [HLA].”).

131 See Gaston, supra note 43, at 2 (“In cadaveric transplantation, it now appears that only the complete absence of HLA mismatches confers a significant survival benefit.”); Ingelfinger, Julie R., Risks and Benefits to the Living Donor, 353 New Eng. J. Med. 447, 447 (2005)CrossRefGoogle ScholarPubMed (“Advances in immunosuppression have changed the criteria for donation of a kidney by a living person, and someone who is … [not] a close HLA match can now donate.”).

132 See Stephen Sheldon & Kay Poulton, HLA Typing and Its Influence on Organ Transplantation, in Transplantation Immunology: Methods and Protocols 157, 166 (Philip Hornick & Marlene Rose eds., 1st ed. 2006) (“If sensitization to any HLA specificities is identified, these can be highlighted as ‘unacceptable antigens’ and avoided as mismatches with any potential donor.”).

133 See Davis & Wolitz, supra note 6 (“[A] positive cross-match is a contraindication [for a kidney transplant] because the likelihood [of rejection] is high.”).

134 See Roth et al., supra note 31, at 4 (“Prior to transplantation, the potential recipient is tested for the presence of preformed antibodies against HLA in the donor kidney. The presence of [such] antibodies, called a positive crossmatch, effectively rules out transplantation.”).

135 See Sack, supra note 85.

136 See id. (“Some [patients], because of previous transplants, blood transfusions or pregnancies, may have developed antibodies that make them highly likely to reject a new kidney.”).

137 See Gentry et al., 2011, supra note 82, at 146 (noting that the largest paired kidney donation included six donors and six recipients in 2008).

138 See id. at 145 (“As a result [of paired kidney donation], many hundreds of transplants have resulted … and [paired kidney donation] programs are active in many countries: the Netherlands, Korea, Canada, the United Kingdom, and Romania.”).

139 See id. at 146 (noting that the limitations of paired kidney donation include the reciprocal match requirements and simultaneous donor nephrectomy requirements).

140 Id.

141 See Ashlagi, I. et al., Nonsimultaneous Chains and Dominos in Kidney-Paired Donation—Revisited, 11 Am. J. Transplantation 984, 984 (2011)CrossRefGoogle ScholarPubMed (noting that simultaneous operations require assembling enough “operating rooms and surgical teams” to perform them).

142 See Gentry et al., 2011, supra note 82, at 146 (“[Eliminating reciprocal matching requirements] is particularly beneficial for pairs with difficult-to-match donors, as well as difficult-to-match recipients.”).

143 See Montgomery, Robert A. et al., Domino Paired Kidney Donation: A Strategy to Make Best Use of Live Non-Directed Donation, 368 Lancet 419, 419 (2006)CrossRefGoogle ScholarPubMed (“[In paired donation programs], more than 50% of the incompatible pairs in the pool remain unmatched [and a high proportion of the recipients in these pairs have] blood types that are hard to match and … HLA sensitisation.”).

144 See id. (explaining that, in a domino paired donation chain, a donor's kidney is given to a recepient who has a willing but incompatible donor with the understanding that the incompatible donor will then donate their kidney to someone else, “producing a domino effect.”).

145 See Ashlagi et al., supra note 141, at 984 (“A sequence of matches initiated by a NDD is called a chain.”).

146 See Adams et al., supra note 87, at 583 (“[T]he NDD volunteers to donate an organ for a recipient that he or she does not know or select.”); Olbrisch et al., supra note 27, at 41-42 (“[An NDD] is someone who wishes to donate an organ to be used by any recipient who needs it, without knowledge of the recipient's need or distress. Most blood donors are [NDDs].”).

147 See Melcher, Marc L. et al., Kidney Transplant Chains Amplify Benefit of Nondirected Donors, 148 JAMA Surgery 165, 166 (2013)CrossRefGoogle ScholarPubMed [hereinafter Melcher et al. 2013] (“Typically, an NDD would present to a transplant center wanting to altruistically donate a kidney to a compatible patient at the top of the DDWL who did not have the benefit of a living donor.”); Wallis et al., supra note 8, at 2094 (“While many programs choose to allocate [NDD] kidneys to the [DDWL], others seek to multiply the gift [by having them] initiate a chain of transplants.”).

148 See Montgomery et al., supra note 143, at 419 (noting that the NDD “initiates a chain of matches”).

149 See Glorie et al., supra note 123, at 815.

150 Gentry et al. 2011, supra note 82, at 147.

151 Montgomery et al., supra note 143, at 419.

152 See Wallis et al., supra note 8, at 2095 (“[DPD chains] bypass the need for reciprocal matching.”).

153 See Gentry et al. 2011, supra note 82, at 146 (“[Eliminating reciprocal matching requirements] is particularly beneficial for pairs with difficult-to-match donors, as well as difficult-to-match recipients.”); Wallis et al., supra note 8, at 2095 (“[DPD chains] provid[e] higher quality matches to participants and allow[] more pairs to profit.”).

154 See Rees et al., supra note 30, at 1099.

155 See id. (“If for some reason, the [NDD] donates to the recipient in Pair 1, but the donor in Pair 1 then fails to donate to the recipient in Pair 2, the outcome will be unfair….”).

156 See Ashlagi et al., supra note 141, at 984 (“Nonsimultaneous chains can be longer than simultaneous chains, since the larger number of operating rooms and surgical teams required by a long chain do not need to be assembled simultaneously.”).

157 See Gentry et al. 2011, supra note 82, at 146 (defining NEAD chains as “nonsimultaneous extended altruistic donor” chains).

158 See Tenenbaum, supra note 125, at 149-50.

159 See id.; see also Glorie et al., supra note 123, at 815; Rees et al., supra note 30, 1099.

160 See Montgomery, supra note 128, at 455 (noting that because the transplants are not simultaneous there is a high possibility of reneging).

161 See Gentry et al. 2011, supra note 82, at 147 (noting that waiting donors in a NEAD chain are called “bridge donors”); see also Wallis et al., supra note 8, at 2094 (explaining that the bridge donor waits for another segment of exchanges).

162 See Ashlagi et al., supra note 141, at 984 (“[Bridge donors can] further extend[] the [NEAD] chain to as yet unidentified patients….”).

163 See id. at 985 (“[T]he NDD initiates a [NEAD] chain consisting of several segments. Each segment is a short simultaneous chain, where the last donor of each segment becomes a bridge donor.”).

164 Tenenbaum, supra note 125, at 149-50 (explaining how a NEAD chain could theoretically continue indefinitely); see Ross et al., supra note 127, at 523 (explaining that bridge donors renege on their promises to donate because of “their own health issues or the difficulty in donating due to other competing obligations that developed when they are finally contacted”).

165 Byron Pitts et al., Donating a Kidney to a Complete Stranger in Order to Save a Loved One, ABC News (Apr. 14, 2015, 4:07 AM), http://abcnews.go.com/Health/donating-kidney-complete-stranger-order-save-loved/story?id=30288400 [https://perma.cc/W7BS-95LV] (“[The longest multi-national kidney transplant chain in the United States consisted of] 34 kidneys … swapped between 26 different hospitals over the course of three months.”).

166 See Melcher, M.L. et al., Letter to the Editor, We Need to Take the Next Step, 16 Am. J. Transplantation 3581, 3581 (2016)CrossRefGoogle ScholarPubMed [hereinafter Melcher et al. Letter to the Editor 2016] (“Nondirected [living donors] are so important because they can start NEAD chains that lead to more transplants for blood type O and highly sensitized patients.”).

167 See, e.g., Wallis et al., supra note 8, at 2094 (noting that nonsimultaneous altruistic donor chains maximize quality and quantity).

168 Rees et al., supra note 30, at 1098; see also Wallis et al., supra note 8, at 2097 (“[While a NEAD chain] has the potential for ‘bridge’ donor reneging, … this controversial risk of inequity has been justified by a belief that nonsimultaneous chains would provide better utility.”).

169 Wall et al., supra note 22, at 2820 (noting how donor withdrawal has been minimized because of decreased waiting times.).

170 See Woodle, E.S. et al., Ethical Considerations for Participation of Nondirected Living Donors in Kidney Exchange Programs, 10 Am. J. Transplantation 1460, 1465 (2010)CrossRefGoogle ScholarPubMed (“[S]ubstantial waiting periods that [bridge donors] will face may increase the likelihood of backing out….”).

171 See Wallis et al., supra note 8, at 2094 (noting how many of the exchange approaches were combinded in a 13-way exchange).

172 Tenenbaum, supra note 125, at 151 (noting that this approach curbs the number of people that renege).

173 See Gentry et al. 2011, supra note 82, at 147 (“If during a long waiting period some of these bridge donors withdraw or become medically ineligible to donate, the bridge donor's potential contribution will be lost.”).

174 See Paired Donation Networks, Kidney Link, http://kidneylink.org/PairedDonationPrograms.aspx [https://perma.cc/WT9C-ZSED] (listing several organizations and their contact information); see generally Alliance for Paired Kidney Donation, https://paireddonation.org/ [https://perma.cc/YC8T-PP5R] (containing information about their KPD programs); Nat'l Kidney Registry, supra note 62 (containing information about their, KPD, DPD, and NEAD chain programs); Ross et al., supra note 127, at 520 (“In 2013, there were seven active multicenter kidney paired exchange registries in the United States plus several single-center registries.”).

175 See Gentry et al. 2011, supra note 82, at 149 (“[C]orrect optimization algorithms [are] mathematically intricate….”).

176 See Gentry et al. 2011, supra note 82, at 149 (“The best algorithms, known as optimization algorithms, guarantee that no better set of matches could have been found.”); see also Wallis et al., supra note 8, at 2095 (noting how optimization algorithms search for quality matches).

177 See Gentry et al. 2011, supra note 82, at 149 (“Depending on the priorities of the program, a better set of matches might be one in which more recipients underwent transplant, or, alternatively, one in which the same number of recipients were matched, but with more highly sensitized recipients.”); Ross et al., supra note 127, at 523 (“Optimizing chain lengths … is a balance between the length of a chain with capturing hard-to-match pairs, patient sense of urgency, and many logistical issues, particularly as chains are formed that involve hospitals in different parts of the country.”).

178 See Wall et al., supra note 22, at 2818 (“[Kidney exchanges] have facilitated [transplants] for end stage renal disease patients with willing but incompatible living donors.”).

179 See Allen et al., supra note 63, at 531 (“[D]irected donation by spouses and close family members accounts for 87% of living kidney transplants since 1988.”).

180 153 Cong. Rec. 2,195 (2007) (statement of Rep. Dingell); see 153 Cong. Rec. 2,193 (2007) (statement of Rep. Norwood) (“[I]n many cases, those who want to give a kidney to a loved one feel they cannot help because they are not biologically compatible with the patient in need.”); Allen et al., supra note 63, at 531 (“Over 5500 living kidney donor transplants take place each year in the United States, and directed donation by spouses and close family members accounts for 87% of living kidney transplants since 1988.”).

181 See Melcher, M.L. et al., Utilization of Deceased Donor Kidneys to Initiate Living Donor Chains, 16 Am. J. Transplantation 1367, 1367 (2016)CrossRefGoogle ScholarPubMed [hereinafter Melcher et al. Article 2016] (“Donor and recipient chains, assembled by computer algorithms, lead to a remarkable number of kidney transplants and improve opportunities for difficult-to-match candidates and ethnic minorities.”).

182 See Wall et al., supra note 22, at 2818.

183 See Veale et al., supra note 123, at 2118 (“[The NKR,] … the leading multicenter KPD organization, … has facilitated over 2000 transplants.”).

184 See Zenios, Stefanos A. et al., Primum Non Nocere: Avoiding Harm to Vulnerable Wait List Candidates in an Indirect Kidney Exchange, 72 Transplantation 648, 653 (2001)CrossRefGoogle Scholar (explaining that the waiting list time can decrease from between 6.2-15.6%).

185 See, e.g., Steinberg, David, Editorial, Exchanging Kidneys: How Much Unfairness Is Justified by an Extra Kidney and Who Decides?, 44 Am. J. Kidney Diseases 1115, 1115 (2004)CrossRefGoogle ScholarPubMed (emphasizing that the live kidneys that are retrived are from people that probably would not have donated if their family member did not need a kidney).

186 See Adams et al., supra note 87, at 584-85, 587 (emphasizing that “the NDD volunteers to donate an organ for a recipient that he or she does not know or select.”).

187 See Rees et al., supra note 30, at 1099 (“[Some physicians] recommend[] that [NDD] organs should be allocated to the patients on the [DDWL] who have the highest ranking, according to the UNOS point system.”); see also Ross, Lainie Friedman, The Ethical Limits in Expanding Living Donor Transplantation, 16 Kennedy Inst. Ethics J. 151, 166 (2006)CrossRefGoogle ScholarPubMed (“The moral question is whether it is ethically permissible to use [an NDD] as the catalyst for a [kidney chain] … or whether the [NDD] organ should be run immediately against the wait list….”).

188 See Ross et al., supra note 187, at 166 (“From a utilitarian perspective, it makes sense to consider using the [NDD] as a catalyst for a [kidney chain] because it can maximize the number of transplants performed.”).

189 See Gentry, Montgomery & Segev 2011, supra note 82, at 147 (“NEAD chains also shift the benefit of [NDDs] away from recipients on the [DDWL] in favor of recipients with living donors.”).

190 See Wall et al., supra note 22, at 2820 (explaining the utility gained by multiple transplants).

191 Id.

192 See Montgomery, supra note 128, at 454 (“[Allowing NDDs to donate to kidney chains] helps donors to more fully realize their altruism by enabling more than one transplant.”); Rees et al., supra note 30, at 1100 (“If an important benefit for an altruistic donor is psychological, then arguably there is more psychological benefit to be derived from helping a chain of many patients than from helping only one patient.”).

193 See Montgomery, supra note 128, at 454.

194 See, e.g., Steinberg, supra note 185, at 1115 (emphasizing that donors probably would not donate if their family member did not need a kidney).

195 See Rees et al., supra note 30 at 1099-1100 (explaining how the live donations help multiple people by removing individuals from the deceased donor waiting list).

196 See Zenios et al., supra note 184, at 653 (“Those individuals with the highest [sensitivity] will have the longest waiting times even when placed at the top of the UNOS wait list.”).

197 See, e.g., Steinberg, supra note 185, at 1115-16 (explaining how individuals with O type blood may be disadvantaged).

198 See Hartogh, Govert Den, Trading with the Waiting-List: The Justice of Living Donor List Exchange, 24 Bioethics 190, 196 (2010)CrossRefGoogle Scholar (“[LPD was introduced] in order to increase the pool of available organs.”).

199 See Steinberg, supra note 185, at 1116 (“[The intended recipient] does not receive a deceased donor kidney until after their incompatible donor has given a live kidney to a compatible stranger on the deceased donor transplant waiting list.”); see also Ross, supra note 187, at 159 (“[T]he living donor donates to the wait list first, and then his or her intended recipient gets first choice for the next available ABO-identical deceased organ donor.”).

200 See Swati Arora & Kalathil K. Suresh Kumar, Paired Exchange: A New Innovation in Live Donor Kidney Transplantation, J. Nephrology & Therapeutics, June 2014, at 2, 3 (illustrating the benefits of LPD exchanges); Gentry, Sommer E. et al., A Comparison of Populations Served by Kidney Paired Donation and List Paired Donation, 5 Am. J. of Transplantation 1914, 1914 (2005)CrossRefGoogle ScholarPubMed [hereinafter Gentry et al. 2005] (“[List paired exchange] allows the recipient of an incompatible pair to receive priority on the [DDWL] for providing the waitlist with the kidney from his intended live donor.”); Montgomery, supra note 128, at 452 (“[T]he donor's intended recipient receives special status on the [DDWL] expediting their transplant with a deceased donor kidney.”); Roth et al., supra note 31, at 459 (“[In a list paired exchange], the patient in the couple receives high priority on the [DDWL], in return for the donation of his donor's kidney to someone on the queue.”).

201 See Ross, Lainie Friedman & Woodle, E. Steve, Ethical Issues in Increasing Living Kidney Donations by Expanding Kidney Paired Exchange Programs, 69 Transplantation 1539, 1541 (2000)CrossRefGoogle Scholar (noting that a list paired exchange may minimize waiting time for a recipient); Wallis et al., supra note 8, at 2094 (noting that the recipient in a list paired exchange may have a “much shorter waiting time…”).

202 Steinberg, supra note 185, at 1115 n.b.

203 See Gentry et al. 2011, supra note 82, at 147 (“In practice, only unsensitized candidates have been accepted [for LPD], with the justification that a sensitized candidate might wait for an extended period after the paired donor's gift before a compatible deceased donor organ becomes available.”).

204 See Steinberg, supra note 185, at 1115 n.b (explaining the likelihood to receive a kidney is very low for patients with panel reactive antibody levels greater thatn 20%).

205 See Gentry et al. 2011, supra note 82, at 147.

206 See id. (“List paired donation rearranges the usual allocation order for deceased donor organs and thus in the United States requires a local allocation variance from UNOS.”).

207 See Conditions of Participation for Hospitals, 42 C.F.R. § 482.45(b)(1) (2016) (“A hospital in which organ transplants are performed must be a member of the [OPTN] … and abide by its rules.”); Organ Procurement and Transplantation Network, 42 C.F.R. § 121.3(b)(1)(i)-(ii) (2016) (“The OPTN shall admit and retain as members the following: (i) All organ procurement organizations; (ii) Transplant hospitals participating in Medicare or Medicaid….”); Glazier & Sasjack, supra note 29, at 89 (“[T]he OPTN ultimately has authority to enforce its policies by denying membership … to transplant centers that do not comply.”); Baginski, Wojciech, Hastening Death: Dying, Dignity and the Organ Shortage Gap, 35 Am. J.L. & Med. 562, 578 (2009)CrossRefGoogle ScholarPubMed (“The OPTN can impose sanctions on its members for not complying with its enacted policies.”).

208 See Reviews, Evaluation, and Enforcement, 42 C.F.R. § 121.10(c)(1) (2015) (“[N]oncompliance with [UNOS] rules [may result in] removal of designation as a transplant program…, termination of a transplant hospital's participation in Medicare or Medicaid,…[and] termination of an OPO's reimbursement under Medicare and Medicaid….”); see also Glazier & Sasjack, supra note 29, at 89 n.141 (“[M]embership with the OPTN is a Medicare condition of participation for hospitals that perform organ transplants[.]”).

209 See Designated Transplant Program Requirements, 42 C.F.R. § 121.9(a)(1), (3) (2015) (“To receive organs for transplantation, a transplant program … that is a member of the OPTN … shall: (1) Be a transplant program approved by the Secretary [of HHS] for reimbursement under Medicare; or … (3) Be a transplant program in a Department of Veterans Affairs, Department of Defense, or other Federal hospital.”).

210 See id. §§ 121.8(a)(5), (b) (“[The OPTN] shall develop…policies for the equitable allocation of cadaveric organs among potential recipients” and “[a]llocation policies shall be designed to achieve equitable allocation of organs among patients….”).

211 See id. § 121.8(g).

212 See Ross, supra note 187, at 161 (“Region 1 received a variance before they began performing list-paired exchanges.”); Veatch, R.M., Editorial, Organ Exchanges: Fairness to the O-Blood Group, 6 Am. J. Transplantation 1, 1 (2006)CrossRefGoogle ScholarPubMed [hereinafter Veatch 2006] (“[S]everal transplant programs have obtained variances to permit potential living donors who are incompatible with their intended recipients to swap their organ for one in the pool of cadaver organs.”).

213 See Zenios et al., supra note 184, at 648.

214 See Gentry et al. 2005, supra note 200, at 1914 (“[A] major concern[ ] that] ha[s] been raised about the equity of LPD [is that] a deceased donor kidney has a considerably shorter half-life when compared to a live donor kidney.”); see also Montgomery, supra note 128, at 452-53 (“An exchange of a live donor kidney for a deceased donor kidney with a significantly shorter predicted half-life may be hard to justify.”).

215 See Delmonico et al., supra note 124, at 1632 (“[List exchanges require] appropriate disclosure of the difference in outcome that can be achieved by live versus deceased donor transplantation”); Steinberg, supra note 185, at 1118 (“The[] inequities [of having a donor give a live kidney while the paired recipient receives a deceased donor kidney], although significant, should be known in advance to the live donor, who can consider [the inequity] acceptable or refuse to donate.”).

216 See Delmonico et al., supra note 124, at 1632 (“The comparative rate of mortality that is associated with dialysis versus transplant is substantial at every age group….”).

217 See Gentry et al. 2011, supra note 82, at 147 (“Unrestricted [LPD] would disproportionately harm type O recipients on the waiting list….”); see also Wallis et al., supra note 8, at 2094 (“[M]any fear list exchanges promote an unacceptable disadvantage to blood type O candidates on the wait-list….”).

218 See Morley, supra note 28, at 227 (“[B]lood type A (the patient has only A antigens), blood type B (the patient has only B antigens), blood type AB (the patient has both A and B antigens), and blood type O (the patient has no antigens.”); Roth et al., supra note 31, at 460.

219 See Ayres et al., supra note 28, at 817 (“Antigens that distinguish blood types A, B, and O are also present on the surface of kidney tissue.”); see also Morley, supra note 28, at 227 (stating that the composition of A and B antigens determines a person's blood type).

220 Morley, supra note 28, at 227-28.

221 See id. at 228; see also Ayres et al., supra note 28, at 817 (“Persons who are type O are said to be ‘universal’ donors, but can receive kidneys (or blood) only from others of the same blood type.”).

222 Morley, supra note 28, at 228.

223 See Ayres et al., supra note 28, at 817 (“[A] small fraction of persons possess both the A and B antigens—blood type AB—and are universal recipients.”).

224 See Advisory Comm. on Organ Transplantation, U.S. Dep't of Health & Human Servs., Conference Call: March 7, 2013, https://www.organdonor.gov/legislation/acotmarch2013notes.html [https://perma.cc/EV5V-FWC7] (“[Some] blood type B candidates … can accept kidneys from subtypes of blood type A donors….”).

225 E.g., Blood Facts and Statistics, Am. Red Cross, http://www.redcrossblood.org/learn-about-blood/blood-facts-and-statistics [https://perma.cc/DB4K-RKZE] (“About 45 percent of people in the U.S. have type O (positive or negative) blood. This percentage is higher among Hispanics—57 percent, and among African Americans—51 percent.”).

226 See Ross & Woodle, supra note 201, at 1539 (“[B]lood group O donors are universal donors and can give to any ABO recipient”).

227 See Gentry et al. 2011, supra note 82, at 145 (“[R]elatively few type O donors will be found incompatible with their intended recipients … so type O donors will be under-represented in incompatible pairs.”).

228 See Hartogh, supra note 198, at 191 (“If a candidate-donor has blood group O, he will be a suitable donor to his partner, whatever the blood group of the partner.”).

229 See Ross & Woodle, supra note 201, at 1539 (“…O donors may donate directly [to their intended recipients] unless there is a positive crossmatch.”); see also Segev et al., supra note 129, at 505 (“[I]ncompatible pairs only contain O donors when there is a positive crossmatch.”).

230 See Delmonico et al., supra note 124, at 1632 (“The biological reality is that an O blood type live donor is rarely available unless the recipient is crossmatch incompatible with the donor.”).

231 Roth et al., supra note 31, at 461 (“[T]ype O patients can only receive type O kidneys.”); Davis & Wolitz, supra note 6.

232 See Montgomery, supra note 128, at 452 (“When compared to the general donor/recipient population, incompatible pools contain a dramatic … skewing towards a greater percentage of hard-to-match O recipients … and fewer valuable O donors….”).

233 See McMahon, supra note 122, at 3 (“[M]ore than two-thirds of incompatible donor-recipient pairs involve a recipient of blood group O.”).

234 See Roth et al., supra note 31, at 461-62 (“[A] type O donor can directly donate to his intended recipient unless there is a positive crossmatch.”).

235 See Gentry et al. 2005, supra note 200, at 1916 (“[P]opulations of incompatible kidney pairs who do not match after KPD (i.e. the ‘KPD waiting list’) are heavily weighted to type O recipients (76%) and underrepresented by their type A counterparts (16%)….”).

236 See id. at 1917.

237 Gentry et al. 2011, supra note 82, at 145.

238 See id.

239 See Glander, Petra et al., The ‘Blood Group O Problem’ in Kidney Transplantation—Time to Change?, 25 Nephrology Dialysis Transplantation 1998, 2000 (2010)CrossRefGoogle Scholar (finding patients with type O blood wait about 85 months for a donor kidney compared to patients with other blood types who wait about 59 months).

240 See Gentry et al. 2011, supra note 82, at 145; see also Gentry, Sommer E. et al., Expanding Kidney Paired Donation Through Participation by Compatible Pairs, 7 Am. J. Transplantation 2361, 2361 (2007)CrossRefGoogle ScholarPubMed [hereinafter Gentry et al. 2007] (“…O recipients in the KPD pool who must rely on scarce O donors will have difficulty finding a match.”); see also Montgomery, supra note 128, at 455 (“[Thirty percent] of a KPD pool will be made up of O recipients with A donors and these patients will have prolonged waiting times….”).

241 See Hartogh, supra note 198, at 196 (“…O-patients who have to wait longer have an increased risk of dying on the waiting list or of reaching the stage at which they are no longer eligible for transplantation….”).

242 See Steinberg, supra note 185, at 1116 (“[P]atients with blood type O, who already have relatively long waiting times [because they are] less likely to match with their live donor [will disproportionately participate in LPD].”).

243 See Ross, supra note 187, at 159.

244 See id. at 161.

245 See id.

246 See Hartogh, supra note 198, at 196 (“[List paired donation] is not a form of illegitimate favoritism.”).

247 See id. (“[List paired donation] simply gives priority to [any] recipients on whose behalf a kidney is being offered to the organ pool.”).

248 See id. (“[List paired donation was] not introduced for partial reasons, but in order to increase the pool of available organs.”).

249 See id. at 197 (explaining LPD was created to solve the concerns that arise when the recipient has type O blood and the donor does not).

250 See Steinberg, supra note 185, at 1116 (“If we consider all people waiting for a deceased kidney as a group, [LPD] is not unfair.”).

251 See Gentry et al. 2005, supra note 200, at 1920.

252 See Ross, supra note 187, at 159.

253 See Hartogh, supra note 198, at 191 (“On the O-part of the list, however, one person will move from a lower to a very high place on the list, with the result that all [blood type O] patients between these two places will move down a place.”); see also Segev et al., supra note 129, at 505 (“[M]ost incompatible pairs participating in LPD consist of type O recipients with non-O donors, and as such a deceased donor kidney from the O list is exchanged for a live donor kidney given to the A or B list.”).

254 See Hartogh, supra note 198, at 191 (“[In general, LPD] will tend to have negative results for O-patients and positive results for others.”); see also Ross, supra note 187, at 159 (“[L]ist paired exchanges] would result in … wait-list candidates of blood type O having their wait prolonged because the living donor's intended recipient gets priority for the next deceased donor organ of blood type O.”); see also Veatch 2006, supra note 212, at 1 (stating patients with type O blood who do not have a living donor face increased wait times up to 9.8% for transplants).

255 See Steinberg, supra note 185, at 1118 (“The most important ethical issue in [LPD] is the likely harm to blood-group-O patients.”).

256 Hartogh, supra note 198, at 191.

257 Id.

258 See Delmonico et al., supra note 124, at 1632 (“[M]ost candidates … who were bypassed … waited only several weeks to months longer than they would have without the exchange process….”).

259 See McMahon, supra note 122, at 3 (“Arguably, it would be unethical to further delay transplantation for … those waiting to receive blood type O organs off of the traditional wait list….”).

260 See Hartogh, supra note 198, at 191 (“[T]he more significant the whole [LPD] program will be in terms of its yields, the more significant will be the total disadvantage to each particular O-patient on the waiting list.”); Steinberg, supra note 185, at 1115–16 (“[With LPD,] those with blood type O … will be bumped, perhaps repeatedly…. This will increase the wait for blood-type-O patients already on the [DDWL].”).

261 Steinberg, supra note 185, at 1118 (“[In a LPD system, m]aximal utility … would be obtained, but at the cost of maximal unfairness.”).

262 Veatch 2006, supra note 212, at 1 (“[T]he average person benefits and therefore [LPD] would satisfy utility maximizers….”); see also Hartogh, supra note 198, at 197 (“In a situation of extreme scarcity it is a hard decision to forego any available source of organs.”).

263 See Adams et al., supra note 87, at 587 (“[T]he opportunity to provide for two transplant recipients instead of one is the impetus to proceed with [LPD].”); Steinberg, supra note 185, at 1115 (“Because a live kidney is retrieved from someone who otherwise probably would not have donated, [LPD] increases the total number of kidneys available for transplantation.”).

264 See Steinberg, supra note 185, at 1115 (“Because kidney transplantation obviates the need for dialysis and, in occasional cases, can be life saving, the protocol has utilitarian value.”).

265 Veatch, Robert M., Egalitarian and Maximin Theories of Justice: Directed Donations of Organs for Transplant, 23 J. Med. & Phil. 456, 460 (1998)CrossRefGoogle Scholar [hereinafter Veatch 1998].

266 See Hartogh, supra note 198, at 194.

267 Steinberg, supra note 185, at 1117.

268 See Ross, Lainie Friendman & Zenios, Stefanos, Practical and Ethical Challenges to Paired Exchange Programs, 4 Am. J. Transplantation 1553, 1553 (2004)CrossRefGoogle ScholarPubMed (“[The] the most serious challenge [of LPD] is the inequities incurred by candidates with blood type O who are worst-off (i.e., have the longest waiting times….)”; Veatch 2006, supra note 212, at 1 (“[LPD] further disadvantag[es] an already disadvantaged group.”).

269 See John Rawls, Justice as Fairness: A Restatement 42-43 (Erin Kelly, ed., 2001) (“[I]nequalities … are to be to the greatest benefit of the least-advantaged members of society….”); Noush, Sumaya, A Storied Past Demands Greater Access to Health Care Now and Into the Future, 24 Annals Health L.: Advance Directive 53, 67 (2014)Google Scholar (“…Rawls holds that [it is important to] distribu[e] limited resources in a way that minimizes … potential harms and maximizes the prospects of individuals who are the worst off.”); Veatch 1998, supra note 265, at 456 (“…Rawlsian principles would tend to create practices that would improve the lot of the least well off and thereby make people more equal.”).

270 See Hartogh, supra note 198, at 194 (“[With LPD, O-patients are] relatively disadvantaged for reasons which have nothing to do with their own ‘deserts.’”); Ross & Zenios, supra note 268, at 1553 (“Justice as fairness only permits policy changes that benefit those who are worst off (i.e., O waitlist candidates who already have the longest waiting time).”).

271 See Ross & Zenios, supra note 268, at 1554 (“[L]ist paired exchange … harms the worst-off group and is therefore unjust.”); Zenios et al., supra note 184, at 648-49 (“[List paired donation] would not be justifiable as it harms an already vulnerable population.”).

272 See Thomson, Judith Jarvis, Turning the Trolley, 36 Phil. & Pub. Aff. 359, 361, 373 (2008)Google Scholar [hereinafter Thomson 2008].

273 Id. at 361.

274 Id.

275 See id. at 362.

276 See id. at 373.

277 Id. at 360, 362.

278 Foot, Philippa, The Problem of Abortion and the Doctrine of the Double Effect, 5 Oxford Rev. 5, 11 (1967).Google Scholar

279 Id.

280 See Thomson, supra note 272, at 360.

281 See Thomson, Judith Jarvis, The Trolley Problem, 94 Yale L.J. 1395, 1404 (1985)CrossRefGoogle Scholar [hereinafter Thomson 1985] (“[I]f one would infringe a right in or by acting, then it is not sufficient justification for acting that one would thereby maximize utility.”); see also id. at 1408 (“Rights trump utilities.”).

282 Id. at 1411.

283 Id.

284 See id.

285 Id.

286 See id.

287 See National Organ Transplant Act of 1986, 42 U.S.C. § 273(b)(3)(E) (2012).

288 See Steinberg, supra note 185, at 1117; Wall et al., supra note 22, at 2820 (“Waiting time … is the primary principle for the allocation of kidneys from the [DDWL].”).

289 See Steinberg, supra note 185, at 1117 (“[I]nequity and unfairness refer to a deviation from rules intended to be uniformly applied.”); see also Hartogh, supra note 198, at 196 (“[List paired donation] allows exceptions to be made on general rules of allocation….”); Roth et al., supra note 31, at 461 (“[List paired exchange] can harm type O patients who have no living donors [because] they will be losing their priority to type O patients whose incompatible donors donate to the [DDWL]….”).

290 See Living Donors, supra note 5.

291 See Steinberg, supra note 185, at 1116 (“[List paired donation was] designed ‘to increase organs available for transplantation generally.’”); see also Hartogh, supra note 198, at 196 (noting that LPD provides a “special advantage” for those recipients who have incompatible live donors).

292 See generally Ross & Zenios, supra note 268, at 1553 (“Although the number and quality of kidneys available for individuals on the waitlist could be increased by [LPD], and overall waiting time decreased, [LPD] is unjust.”); Steinberg, supra note 185, at 1117 (“Giving a kidney to [a recipient] who has not duly waited his or her turn in line is unfair because it trumps the rights of those who have followed what they have understood to be the rules.”); Zenios et al., supra note 184, at 653 (“Regardless of how many additional kidneys can be procured, it would be ethically problematic if the overall waiting time were reduced at the expense of standard blood type O [candidates on the DDWL].”).

293 Steinberg, supra note 185, at 1116.

294 Id. at 1117; see also Veatch 2006, supra note 212, at 1 (“[S]ome theorists would resolve conflicts between fairness and utility by balancing the competing claims—letting modest unfairness persist in order to gain greater overall benefit.”).

295 See Steinberg, supra note 185, at 1119 (noting that if time delays for those with blood type O are limited, LPD should be considered morally permissible; “utility is respected because more kidneys are retrieved, but equity is also respected because unfairness is limited.”).

296 Thomson 1985, supra note 281, at 1411. No changes r.4.2

297 See Organ Procurement and Transplantation Network § 8 (indicating that kidneys from donors with blood type O are allocated to candidates with blood type O unless there is a zero antigen mismatch); Smith et al., supra note 32, at 3193 (“A zero antigen mismatch is defined as ABO blood type being compatible between a candidate and a donor, and the absence of any donor antigens (among the six HLA … antigens)….”); see also Ayres et al., supra note 28, at 821 (indicating that UNOS's rules only allow blood type O kidneys to be transplanted into patients with blood type O).

298 See Davis & Wolitz, supra note 6.

299 Compare Ayres et al., supra note 28, at 821, 862-63 (noting that because blacks “are almost twice as likely as whites to have blood type B,” have fewer donors, and are disproportionately represented on the DDWL, those with B blood are “disadvantaged by the O rule”), with Odds for Receiving a Kidney Transplant Now Equal for Black, White and Hispanic Candidates, UNOS, https://www.unos.org/odds-equal-of-kidney-transplant-for-minorities/ [https://perma.cc/4CJW-TZK8] (July 12, 2017) (“Recent improvements in national kidney transplant policy have evened the rates at which African-American, Hispanic and Caucasian transplant candidates receive kidneys from deceased donors….”).

300 Martin & Danovitch, supra note 12, at 538 (“In 2015, approximately 40% of kidney transplants worldwide were made possible by living donors … [i]n the European Union, the United States, and Australia, living donors enabled 20 to 30% of total kidney transplants.”); Rosen et al., supra note 59, at 720 (noting that 40% of kidney donations are from live donors).

301 See Ross & Woodle, supra note 201, at 1542 (“Given the real concerns of increased waiting time for O recipients, one could argue that the potential O blood group exchange donors should be used preferentially on the basis of utility and justice.”); see also Veatch 2006, supra note 212, at 2.

302 See Ross & Woodle, supra note 201, at 1542.

303 See id. at 1542; Zenios et al., supra note 184, at 654 (“[A] policy that preferentially selects living O donors, when available, can minimize if not completely neutralize [the] negative impact [of LPD on O recipients on the DDWL].”).

304 See Veatch 2006, supra note 212, at 2; see also Ross & Woodle, supra note 201, at 1542 (“Although the selected [O] donor may be given many opportunities to renege, his or her selection by the transplant team may be interpreted quite coercively.”).

305 See Veatch 2006, supra note 212, at 2 (“[M]any of these O-organs now ‘squandered’ on non-O recipients could find their way to O-recipients who would otherwise be forced to obtain organs from the pool created by deceased donors.”).

306 Id. at 2.

307 See Gentry et al. 2011, supra note 82, at 144; Gentry et al. 2007, supra note 240, at 2362 (“[M]any compatible donor/recipient pairs could obtain a meaningful predicted graft survival benefit in recompense for the additional complexity of paired donation.”); Veatch 2006, supra note 212, at 2; see also Keith & Vranic, supra note 4, at 691 (“Recipients with high levels of sensitization to their donor are at higher risk of rejection, require more immunosuppression, and have less optimal allograft outcomes.”).

308 Gentry et al. 2011, supra note 82, at 145–46; see also Montgomery, supra note 128, at 454.

309 See Durand, Céline, Duplantie, Andrée & Fortin, Marie-Chantal, Transplant Professionals' Proposals for the Implementation of an Altruistic Unbalanced Paired Kidney Exchange Program, 98 Transplantation 754, 755 (2014)CrossRefGoogle ScholarPubMed; Wall et al., supra note 22, at 2818.

310 Wall et al., supra note 22, at 2818.

311 See Veatch 2006, supra note 212, at 2; see also Ross et al., supra note 127, at 521 (“The main ethical problem with the participation of compatible pairs in chains and exchanges is how to invite the compatible pair to participate in a way that does not make the pair feel undue pressure”).

312 See Veatch 2006, supra note 212, at 2.

313 See Gentry et al. 2011, supra note 82, at 147; see also Hartogh, supra note 198, at 197.

314 See Gentry et al. 2011, supra note 82, at 147 (“[T]ype O recipients are the only group for which the drawbacks of [LPD] are outweighed by a greater probability of transplant.”); see also Hartogh, supra note 198, at 197.

315 See Chkhotua, A., Paired Kidney Donation: Outcomes, Limitations, and Future Perspectives, 44 Transplantation Proc. 1790, 1791 (2012).CrossRefGoogle ScholarPubMed

316 See id.

317 See Hartogh, supra note 198, at 197.

318 See Wall et al., supra note 22, at 2821.

319 See Melcher et al. Article 2016, supra note 181, at 1367 (“Currently, the number of KPD chains is limited by the number of chain-initiating kidneys (CIKs) from [NDDs].”); Wall et al., supra note 22, at 2822 (noting that one limitation on the number of kidney chains is the lack of NDDs).

320 See Veale et al., supra note 123, at 2117 (“[Voucher programs can motivate] donors who fear that with advancing age they will become unable to donate… [and] people who are anticipating life events such as relocation, marriage, or childbirth that could affect their donation candidacy….”).

321 See Living Donors, supra note 5 (citing two, rather than three, types of ADP cases: “(1) Short term cases, where the intended recipient is on dialysis or in imminent need of a kidney transplant, and…(3) Voucher cases….” The first two types of ADP discussed in this article would arguably fit within “short term cases,” the first type of ADP listed by the NKR).

322 Wall et al., supra note 22, at 2821.

323 See id.

324 See Wallis et al., supra note 8, at 2094; see also Gentry et al. 2011, supra note 82, at 147 (stating that waiting donors in a NEAD chain are referred to as “bridge donors”).

325 Veale et al., supra note 123, at 2117.

326 See Wall et al., supra note 22, at 2821.

327 See Flechner, S.M. et al., The Incorporation of an Advanced Donation Program Into Kidney Paired Exchange: Initial Experience of the National Kidney Registry, 15 Am. J. Transplantation 2712, 2712 (2015).CrossRefGoogle ScholarPubMed

328 See Wall et al., supra note 22, at 12821.

329 Id.

330 See id.

331 See id.

332 Id.

333 See Veale et al., supra note 123, at 2116 (“[V]oucher recipients are not in need of a kidney transplant and may never need a kidney transplant.”); see also Info About the Voucher Program, Nat'l Kidney Registry, http://www.kidneyregistry.org/info/voucher-program [https://perma.cc/V6GT-X8YH] (“Some Voucher donors have donated 20+ years before their intended recipient is expected to need a transplant….”).

334 See Veale et al., supra note 107, at 6 (“[D]onors in the voucher program function as [NDDs] by initiating chains without adding a paired recipient to the current chain.”).

335 See id. at 2119; Kristen Fischer, Donate a Kidney Now, Get a Voucher for One Later, Healthline (July 15, 2016), https://www.healthline.com/health-news/donate-kidney-now-get-one-later [https://perma.cc/CXW3-TWD8].

336 See Veale et al., supra note 107, at 2116 (“When a voucher is redeemed, a future chain of transplantation will end by providing the voucher recipient with a compatible kidney.”).

337 Fischer, supra note 335.

338 See Veale et al., supra note 107, at 2116; see also Veale, supra note 1

339 See Wall, Veale & Melcher, supra note 16, at 12 (“If it were not for the voucher program, the grandfather would likely have become ineligible to be a living kidney donor with advancing age.”).

340 See Veale et al., supra note 123, at 2116.

341 See id. (“In December 2014, [Broadman] underwent a living donor nephrectomy at UCLA, initiating a transplant chain with three recipients, who discontinued dialysis and were removed from the [DDWL].”).

342 Sally Satel, Vouchers and Incentives Can Increase Kidney Donations and Save Lives, STAT News (Sept. 13, 2016), https://www.statnews.com/2016/09/13/kidney-donations-transplant-vouchers-incentives/ [https://perma.cc/9V8G-59DB] (“The concept [of vouchers] has since been adopted at [several] medical centers and has been formalized under the umbrella of the private [NKR's] advanced donation program.”); Wall et al., supra note 22, at 2821 (“[The NKR] is currently the only kidney exchange consortium offering [ADP].”).

343 Veale et al., supra note 123, at 2118; see Flechner et al., supra note 327, at 2713. (“The [NKR] is a voluntary network of 65 transplant centers in 28 states.”).

344 Because the voucher program is so new, there appears to be some confusion concerning whether the ADP donor can have a maximum of one or five intended recipients. Compare Kidney Voucher, UCLA Health, https://www.uclahealth.org/transplants/kidney-exchange/giftcertificateprogram [https://perma.cc/WZ2N-ADJU] (“A renal allograft can only be provided to the pre-determined intended recipient identified on the consent form.”), and Voucher Program, supra note 333 (“An ADP donor may identify one intended recipient.”), with Nat'l Kidney Registry, Advanced Donation Program: Informed Consent, https://www.kidneyregistry.org/docs/ADP_Consents.pdf (last visited Jan. 26, 2018) [hereinafter Informed Consent] (“When an ADP Donor has multiple Intended Recipients, the first appropriate candidate for transplant will get the ADP kidney.”), and Fischer, supra note 335 (noting that Jeffrey Veale—a transplant surgeon at UCLA, who worked with Broadman to start the voucher program—stated that “a donor can add up to five people onto a voucher.”); see also Ross et al., supra note 127, at 522 (noting that voucher programs “allow individuals to donate a kidney in exchange for a voucher for one of up to five specified individuals who might require a kidney transplant in the future”).

345 Voucher Program, supra note 333; see also Fischer, supra note 335 (“Potential recipients must have kidney disease….”).

346 See Veale et al., supra note 123, at 2116 (“[The voucher] has no monetary value and [cannot be] transferred to another patient.”); Voucher Program, supra note 333 (“The Voucher expires when the intended recipient expires and it cannot be transferred.”); Martin & Danovitch, supra note 12, at 541 (“Additional beneficiaries cannot be added later, and vouchers cannot be withdrawn, are non-transferable, and expire on the death of the intended recipient.”).

347 Informed Consent, supra note 344; see also Fischer, supra note 335 (“[T]he voucher can be used only by the first person [on the voucher] who needs it.”); Martin & Danovitch, supra note 12, at 541 (“There is no prioritization of beneficiaries when more than one is designated [on the voucher], with the first to require transplantation benefiting from the voucher”).

348 Fischer, supra note 335.

349 See Voucher Program, supra note 333 (“The intended recipient is required to provide government photo identification and a blood sample so that the HLA and blood type can be confirmed before a Voucher [ ] can be redeemed.”).

350 See National Organ Transplant Act of 1986, 42 U.S.C. § 274e(a) (2012) (“It shall be unlawful for any person to knowingly acquire, receive, or otherwise transfer any human organ for valuable consideration for use in human transplantation if the transfer affects interstate commerce.”); Veale et al., supra note 123, at 2118 (noting that donors in the voucher program do not receive any monetary or other compensation for their donation and the “voucher has no cash value and cannot be sold or bartered to another person”); see also Fischer, supra note 335 (“Vouchers cannot be sold to another person and cannot be withdrawn.”).

351 See, Veale et al., supra note 123, at 2119.

352 See Liu, W., Krawiec, K.D. & Melcher, M.L., Is Informed Consent Enough?, 16 Am. J. Transplantation 1038, 1038 (2016)CrossRefGoogle Scholar; Wall et al., supra note 22, at 2821.

353 See Wall et al., supra note 22, at 2821.

354 See Ashlagi et al., supra note 141, at 984 (“[W]hen a chain begins with a NDD, the cost of a break in the chain is [reduced because] no patient-donor pair needs to give a kidney before they receive one.”); Wall et al., supra note 22, at 2821 (“Advanced donation occurs when an individual donates to a kidney exchange program prior to his or her paired recipient's transplant.”).

355 See Wall et al., supra note 22, at 2821.

356 See, e.g., Healy, Kieran & Krawiec, Kimberly D., Custom, Contract, and Kidney Exchange, 62 Duke L.J. 645, 658 (2012)Google ScholarPubMed (“[In a traditional kidney chain,] no individual in the chain is irreparably harmed [if the donor reneges because] no pair has lost a kidney prior to receiving one, and each thus always retains the ‘bargaining chip’ of the donor's kidney, enabling them to participate in future swaps and chains.”).

357 Info for Centers, Nat'l Kidney Registry, https://kidneyregistry.org/transplant_center.php [https://perma.cc/N3JN-X96Z].

358 See Wall et al., supra note 22, at 2821.

359 See Flechner et al., supra note 327, at 2713 (“Once the ADP donor donated … the paired recipient was placed into the NKR computer matching algorithm to end the next available chain, according to blood group and NKR Medical Board priorities for ending chains.”); Wall et al., supra note 22, at 2821.

360 Flechner et al., supra note 327, at 2713 (“The role of the ADP donor to begin or sustain a chain of KPD transplants is optimized to facilitate the maximal number of transplants….”).

361 Id. at 2712.

362 Veale et al., supra note 123, at 2116-17 (noting that Broadman initiated a chain of three transplants, the second voucher donor initiated a chain of eight transplants, and the third donor initiated a chain of 14 transplants).

363 See Wall et al., supra note 22, at 2821 (“In ADP, there is uncertainty about when the paired recipient will get a kidney transplant.”).

364 Info for Centers, supra note 357; see also Veale et al., supra note 123, at 2118 (“A candidate redeeming a voucher is the third of six categories in the current priority….”).

365 See Liu et al., supra note 352, at 1038 (“Both how the patient is prioritized and the waiting time for ADP patients are unclear…. ‘Prioritized opportunity’ is not defined….”).

366 See Rees et al., supra note 30, at 1100 (“In addition to increasing the quantity of living-donor transplantations, NEAD chains may improve the quality of the matches.”).

367 Info for Centers, supra note 357 (“[M]atch offers shall be selected to facilitate the most possible transplants except when difficult to match pairs can be matched.”); see also Flechner et al., supra note 327, at 2713 (“The role of the ADP donor … is optimized to facilitate the maximal number of transplants….”). Flechner states in his article that “most often” the ADP recipient receives a kidney from the end of “a chain that may be quite deep and may extend over several months.” This statement indicates that most ADP recipients receive kidneys at the end of NEAD chains. Id. at 2715.

368 See Fumo, D.E. et al., Historical Matching Strategies in Kidney Paired Donation: The 7-Year Evolution of a Web-Based Virtual Matching System, 15 Am. J. Transplantation 2646, 2647 (2015).CrossRefGoogle ScholarPubMed

369 See Montgomery, supra note 128, at 455 (“…NEAD will stall after several iterations due to the appearance of a donor with a difficult-to-match blood type.”).

370 See Info for Centers, supra note 357.

371 See Gentry et al. 2011, supra note 82, at 145 (“[R]elatively few type O donors will be found incompatible with their intended recipients.”).

372 See Melcher et al. Article 2016, supra note 181, at 1368 (“[B]lood type O patients … generally can be transplanted only utilizing blood type O donors, who are most in demand.”).

373 See Melcher et al. Letter to the Editor 2016, supra note 166, at 3581.

374 See id. (“Nondirected [live donors] are so important because they can start NEAD chains that lead to more transplants for blood type O and highly sensitized patients.”); Wall et al., supra note 22, at 2823 (“Blood type O kidneys will be in highest demand for chain initiation….”).

375 See Wall et al., supra note 22, at 2823.

376 See id. at 2820.

377 Id.

378 See id.

379 See Flechner et al., supra note 327, at 2715 (“As one would predict, blood group O recipients and highly sensitized patients should expect the longest wait times.”); Veale et al., supra note 123, at 2118 (“[H]ighly sensitized and ‘O’ blood group candidates will be a concern for voucher programs.”).

380 See Keith & Vranic, supra note 4, at 684 (“[F]or patients seeking transplant who are highly sensitized, wait times have traditionally been long and options limited.”); see also id. at 687 (“[H]ighly sensitized candidates are less likely to find donors and accumulate on the [DDWL]….”); see also Melcher et al. Letter to the Editor 2016, supra note 166, at 3581 (“[There is a] high number of sensitized patients in the KPD pool.”).

381 See Keith & Vranic, supra note 4, at 689 (noting that participating in KPD exchanges facilitated by the NKR will be “very difficult” for the “very highly sensitized” because of the “large pool size needed to find an acceptable match”).

382 See Veale et al., supra note 123, at 2117 (“[A] voucher can stimulate multiple donations for a patient who may need one or more transplants in a lifetime, increasing the likelihood that some of these vouchers will never be redeemed.”).

383 See id. at 2116.

384 See id.

385 See id.

386 See id.; Ross et al., supra note 127, at 522 (revealing that Garet Hil, the founder of the NKR, was the father in this case who donated a kidney so he could provide a voucher to his daughter in case she needs a second kidney transplant. Hil could not donate directly to his daughter because of a positive crossmatch.).

387 See Veale et al., supra note 123, at 2117.

388 See id.

389 Info for Centers, supra note 357.

390 See Lampros Kousoulas et al., Risk-Adjusted Analysis of Relevant Outcome Drivers for Patients After More Than Two Kidney Transplants, J. Transplantation, Feb. 1, 2015, at 1.

391 See Keith & Vranic, supra note 4, at 684 (“[Sensitization] occurs primarily via three types of exposure (listed here by increasing sensitizing potential): blood transfusions, pregnancy, and solid organ transplant. Rare cases of sensitization can occur without these.”); Sheldon & Poulton, supra note 132, at 167 (“Following a poorly matched kidney transplant, a patient can become highly sensitized, developing antibodies reactive with more than 50% of the donor population.”); Sack, supra note 85 (“Some [recipients], because of previous transplants, blood transfusions or pregnancies, may have developed antibodies that make them highly likely to reject a new kidney.”).

392 See Kousoulas et al., supra note 390, at 1.

393 See Informed Consent, supra note 344.

394 Id.

395 See Flechner et al., supra note 327, at 2716 (“[B]lood group O recipients with high cPRAs[] remain [ ] difficult to match….”).

396 Informed Consent, supra note 344.

397 Id.

398 Id.

399 See Wall et al., supra note 22, at 2821 (“In ADP, there is uncertainty about when the paired recipient will get a kidney transplant.”).

400 See, e.g., Multicare Med. Ctr. v. Dep't of Soc. & Health Servs., 790 P.2d 124, 131 (Wash. 1990) (“[U]nder a unilateral contract, … the offeree must accept [the offer] by performance….”) (citations omitted); see also Strata Prod. Co. v. Mercury Expl. Co., 916 P.2d 822, 827 (N.M. 1996) (“[A] traditional unilateral contract [is one] in which the offeror makes a promise in exchange, not for a reciprocal promise by the offeree, but for some performance.”) (citations omitted).

401 See Healy & Krawiec, supra note 356, at 663, 667 (2012) (“A mere promise alone to make a gift of an organ is not intended to be legally binding…. [I]n practice doctors will not force [donors] to go through with a donation if they really do not want to….”); see also Strata, 916 P.2d at 827 (“[In a unilateral contract,] the offeree accepts the offer by undertaking the requested performance”).

402 See, e.g., Pine River State Bank v. Mettille, 333 N.W.2d 622, 626-27 (Minn. 1983) (noting that the offeree's performance furnishes the consideration necessary for the offer to be enforceable).

403 Liu et al., supra note 352, at 1038 (“Although it is possible that the promise of priority is too vague to rise to the level of contract, if it is a contract, it is unclear what the contract is for.”).

404 See Informed Consent, supra note 344.

405 See Michael Hunter Schwartz & Denise Riebe, Contracts: A Context and Practice Casebook 134 (2009); see also Ross et al., supra note 127, at 527 (“The NKR website explains that ADP donors and their voucher holders should assume that there is a chance the promise cannot be fulfilled, that the agency responsible for providing the kidney may not even exist when the kidney is needed, and that new technologies may make alternative treatments of the kidney disease possible, thus negating the value of the contract.”).

406 See Third Story Music, Inc. v. Waits, 48 Cal. Rptr. 2d 747, 751 (Cal. Ct. App., 2d Dist. 1995) (citing Arthur Linton Corbin, Corbin on Contracts: A Comprehensive Treatise on the Working Rules of Contract Law § 5.28, 149-150 (vol. 3 1960) (“The tendency of the law is to avoid the finding that no contract arose due to an illusory promise when it appears that the parties intended a contract….”)).

407 See Flood v. ClearOne Comms., Inc., 618 F.3d 1110, 1120-21 (10th Cir. 2010) (noting that a court can read into the parties' agreement that already contains some standard that limits the exercise of discretion, and find a duty to exercise that standard only in good faith).

408 See Dobbins, Teri J., Losing Faith: Extracting the Implied Covenant of Good Faith from (Some) Contracts, 84 Or. L. Rev. 227, 252 (2005)Google Scholar (“[Many courts hold that the duty of good faith] encompasses ‘any promises which a reasonable person in the position of the promisee would be justified in understanding were included.’”); Flood, 618 F.3d at 1121-22 (“[By applying the covenant of good faith and fair dealing, the court gives effect to] ‘the reasonable expectations created by the autonomous expressions of the contracting parties….’”).

409 See generally Flood, 618 F.3d at 1121-22.

410 See Flechner et al., supra note 327, at 2716.

411 See Veale et al., supra note 123, at 2119; see also Melcher et al. Article 2016, supra note 181, at 1368 (“[M]ost chains end with the transplantation of a waitlisted candidate who may not have a compatible potential [living donor].”).

412 See Flechner et al., supra note 327, at 2713.

413 See id. at 2713-14; see also Kute, V.B. et al., A Potential Solution to Make the Best Use of a Living Donor-Deceased Donor List Exchange, 16 Am. J. Transplantation 3580, 3580 (2016)CrossRefGoogle ScholarPubMed (“The median wait time in the [NKR] (the largest paired exchange program in the United States) … is … 174 days for pairs that are very hard to match.”).

414 See Wall et al., supra note 22, at 2818 (“KPD programs now encourage compatible pairs to enter the match allowing the recipient to receive a kidney from a better-matched or younger donor.”).

415 Info for Centers, supra note 357; Ross et al., supra note 127, at 523 (“…NKR seeks to maximize the number of transplants in a chain unless a match run allows for a difficult pair to be incorporated into a chain.”); see also Veale et al., supra note 123, at 2116 (“[T]he Registry is committed to taking the steps necessary to provide [voucher recipients with] a transplant….”).

416 See Melcher et al. Letter to the Editor 2016, supra note 166, at 3581 (suggesting that matching algorithms take into account that the majority of patients in most KPD pools are highly sensitized patients and patients with blood type O).

417 See Flechner et al., supra note 327, at 2716 (“Hard-to-match recipients, especially blood group O recipients with high cPRAs, remain [ ] difficult to match….”).

418 Voucher Program, supra note 333.

419 See Voucher Program May Reduce Organ Transplant Waitlist, Save Lives, Fox News (July 14, 2016), http://www.foxnews.com/health/2016/07/14/voucher-program-may-reduce-organ-transplant-waitlist-save-lives.html [https://perma.cc/9279-Z2PD].

420 Flechner et al., supra note 327, at 2716 (“[G]reat care is needed to provide informed consent for the uncertainty of the [ADP] process….”); Martin & Danovitch, supra note 12, at 542 (“It will be some years before sufficient data are available to provide estimates … on the probability of an intended beneficiary benefiting from [ADP]….”).

421 Wall et al., supra note 22, at 2821.

422 See Liu et al., supra note 352, at 1038 (“[In ADP,] the health and/or sensitization of the [ADP recipient] may change, making [him or her] unsuitable for or difficult to transplant.”); Veale et al., supra note 123, at 2118 (“[M]any vouchers will never be redeemed (because relatively few healthy people develop kidney failure)….”).

423 Wall et al., supra note 22, at 2821; Martin & Danovitch, supra note 12, at 542 (noting that vouchers “may complicate some of the longstanding ethical foundations of related living donation, because there is far greater uncertainty concerning the benefits which may accrue … to the donor's intended beneficiary”).

424 See Compatible Pairs, Nat'l Kidney Registry, http://www.kidneyregistry.org/compatible_pairs.php [https://perma.cc/MU77-Y2CF].

425 See Veale et al., supra note 123, at 2119 (“[T]he [NKR] has contributed hundreds of ‘chain-ending’ living donor kidneys to recipients on the [DDWL].”).

426 See Melcher et al. Article 2016, supra note 181, at 1369 (noting that a “simulated allocation model [can be used] to estimate the benefit of ending chains with donors of specific blood types.”).

427 See Flechner et al., supra note 327, at 2715 (“[Advanced donation programs] should come under close scrutiny and oversight in order to protect the integrity of the KPD network, and the safety of the donors and recipients involved in the ultimate decision to proceed.”); Liu et al., supra note 352, at 1038 (“In light of such a complex and uncertain process, we question whether [ADP] informed consent is sufficient to protect the participants and the integrity of the registry.”).

428 See Flechner et al., supra note 327, at 2715 (“The two [ADP] recipients who remain[ed] untransplanted at [the time the article was published] highlight the importance of careful selection of candidates for [ADP].”).

429 See Gentry et al. 2011, supra note 82, at 147 (“In practice, only unsensitized candidates have been accepted [for LPD], with the justification that a sensitized candidate might wait for an extended period after the paired donor's gift before a compatible deceased donor organ becomes available.”).

430 See Flechner et al., supra note 327, at 2716 (“Hard-to-match recipients, especially blood group O recipients with high cPRAs, … should be carefully considered in the ADP selection process.”).

431 See Melcher et al. Letter to the Editor 2016, supra note 166, at 3581 (“[H]ighly sensitized patients and ‘O’ patients with ‘A’ donors … may be better off accepting a [deceased donor kidney] today than waiting for a KPD offer in the future…. [P]atients and donors should be part of the decision-making process as to whether to participate.”); Martin & Danovitch, supra note 12, at 542 (noting that “rigorous consent processes should help to ensure that donors are fully informed of the uncertainties concerning potential benefits to the voucher recipient(s).”); Ross et al., supra note 127, at 533 (“[T]o be successful, public trust must be preserved by ensuring that all stakeholders – living donors, their intended recipients, transplant programs, and society – are fully informed about the relative risks and benefits of ADP participation.”).

432 Veale et al., supra note 123, at 2118-19.

433 See Melcher et al. Letter to the Editor 2016, supra note 166, at 3581 (“[KPD pools will] be concentrated with blood type ‘O’ and highly sensitized potential recipients….”); Wall et al., supra note 22, at 2823 (noting that kidney chains generally end with non-O kidneys that are “return[ed] to the [DDWL]…”).

434 See supra text accompanying notes 271-279; see also Ross et al., supra note 127, at 526 (“To give voucher candidates priority on the deceased donor waitlist would be unfair to those donors who have been waiting and lack a living kidney donor.”).

435 See Wall et al., supra note 22, at 2822 (“[Advanced donation programs] may enable some donor-recipient pairs to gain advantage[s] for hard to match recipients.”).

436 See Gentry et al. 2011, supra note 82, at 144 (“Kidney paired donation (KPD) can circumvent the incompatibility [of donor/recipient pairs] by matching them to another candidate and living donor for an exchange of transplants such that both transplants are compatible.”).

437 Wall et al., supra note 22, at 2822.

438 See id.

439 See id. at 2821 (“‘[S]hort term unmatched’ donation [occurs when] the donor donates a kidney into the [ADP] before their recipient, who needs a kidney transplant, even has a match.”).

440 See id.

441 See Voucher Program, supra note 333 (“The ADP program is unrelated to the U.S. deceased donor system and participation in the ADP program does not confer any wait time points for the [ADP recipient] in the deceased donor system.”).

442 See Wall et al., supra note 22, at 2822 (“[If donor/recipient pairs with O recipients and non-O donors participated in ADP to gain an advantage, the] practice could generate the need for more blood type O chain ending kidneys….”).

443 See Veale et al., supra note 123, at 2118 (“Any organization responsible for a voucher program would be concerned if requests exceed the availability of chain-end donors, resulting in an inability of potential recipients to redeem their vouchers.”).

444 See Wall et al., supra note 22, at 2821 (indicating that if the NKR were to shut down before the ADP recipient receives a kidney, the ADP recipient may or may not be prioritized on the DDWL).

445 See Veale et al., supra note 123, at 2117-18 (mentioning providing voucher recipients with deceased donors).

446 See, e.g., Hartogh, supra note 198, at 194.

447 See supra text accompanying notes 271-279.

448 See Wall et al., supra note 22, at 2823 (“Removing people from the [DDWL] decreases competition [for deceased donor kidneys] who remain on it.”).

449 See id. at 19 (noting that additional transplants for blood type O recipients on the DDWL removes those recipients from the waiting list and decreases competition for type O kidneys among those left on the list).

450 See supra text accompanying notes 291-293.

451 See supra text accompanying notes 312-314; see also Veale et al., supra note 123, at 2119 (mentioning that a variance from UNOS would be necessary before deceased donor kidneys could be provided to voucher recipients and that “[o]btaining a variance from UNOS is likely to take several years….”).

452 See Melcher et al. Article 2016, supra note 181, at 1367 (proposing that deceased donor kidneys be used to initiate kidney chains).

453 See Wall et al., supra note 22, at 2823.

454 See Melcher et al. Article 2016, supra note 181, at 1368 (“[B]lood type O patients with long waiting times … are most vulnerable to being disadvantaged [by deceased-donor-initiated kidney chains]….”).

455 See Wall et al., supra note 22, at 2823.

456 See Melcher et al. Article 2016, supra note 181, at 1368 (“[I]nitiating a chain with [a deceased donor] kidney results in large benefit associated with more transplantations that remove more candidates from the [DDWL]….”); see also Wall et al., supra note 22, at 2823.

457 See Gentry, et al. 2011, supra note 82, at 144.

458 Ross et al., supra note 127, at 523.

459 See Melcher et al. Article 2016, supra note 181, at 1368.

460 Ross et al., supra note 127, at 530-31.

461 See supra Section VII.

462 Alvin Powell, George Church's Scientific Drive, The Harv. Gazette (May 11, 2016), https://news.harvard.edu/gazette/story/2016/05/if-youre-not-failing-youre-probably-not-trying-as-hard-asyou-could-be/ [https://perma.cc/QC6B-GD97].

463 See, e.g., Gina Kolata, Gene Editing Spurs Hope for Transplanting Pig Organs Into Humans, N.Y. Times (Aug. 10, 2017), https://www.nytimes.com/2017/08/10/health/gene-editing-pigs-organ-transplants.html (explaining that, due to recent advances in cloning and gene editing, pig organ transplants may become a viable option for human transplant recipients, however “it may be years before enough is known about the safety of pig organ transplants to allow them to be used widely.”).