1. What are the various categories of living-donor transplants?
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Related donors: Donor and recipient are biologically related.
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Unrelated donors: Donor is not biologically related, but an emotional relationship exists between the donor and recipient (e.g., coworker, classmate, friend).
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Directed anonymous donors: Donor has no relationship to the recipient; the donor learned of the recipient’s situation and decided to donate altruistically.
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Undirected anonymous donors: Donor decides to donate his or her kidney to the waiting list.
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Paired exchange donors: A pair of donor–recipient candidates (from the related or unrelated categories) enters into a scheme in which the donor is exchanged with another donor–recipient candidate pair so as to achieve donor–recipient biologic compatibility of the ABO blood group system and/or negative cross-match reactivity.
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Multiple paired exchange donors: A paired exchange donation that involves more than two donor–recipient candidate pairs.
4. Discuss transplant tourism and the declaration of istanbul.
Transplant Tourism involves organ trafficking and/or transplant commercialism if the resources used for patients from outside a particular country harms the ability of that country to provide transplant services to the native population. Organ trafficking involves living and deceased donors that are coerced, pressured, or in some fashion influenced to donate. The Declaration of Istanbul published in 2008 emphasized that transplant tourism should be prohibited due to ethical considerations and to protect potential donors. There are exceptions; for example, if a donor and recipient are genetically related, they should be allowed to undergo the transplant in a country of their choice. Transplant tourism is legal in China and in Iran. China has a history of procuring organs from executed prisoners, which has been seen as a violation of the Declaration of Istanbul. In Iran, kidney sales are regulated.
5. What are some contraindications for living kidney donation?
The contraindications listed with an asterisk can have further work up, including a kidney biopsy, to determine the candidacy of a potential donor. Other possible contraindications are acceptable depending on the transplant center. For instance, certain centers will accept a Caucasian donor with hypertension if they are over 60 years of age with well-controlled blood pressure on one medication.
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Chronic kidney disease (glomerular filtration rate <80 mL/min per 1.73 m 2 )
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Proteinuria*
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Hematuria*
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Active infection
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Chronic, active viral infections (e.g., HIV, hepatitis B/C)
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Active malignancy
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Family history of renal cell carcinoma
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Hypertension*
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Diabetes
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Urologic abnormalities, including nephrolithiasis*
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Active substance abuse
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Obesity (body mass index >35 kg/m 2 )*
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Deceased donor kidney with a Kidney Donor Profile Index (KDPI) of 0% to 20% is expected to function about 11.5 years, compared to over 12 years for a living donor kidney. Deceased donor kidneys with a KDPI from 21% to 85% are expected to function about 9 years and those kidneys with a KDPI exceeding 85% are expected to function for at least 5.5 years.
6. How is a living kidney donor evaluated to be compatible for a specific recipient? If not compatible, what options are available?
The evaluation of a potential living kidney generally begins with an assessment of the donor and recipient blood groups and a cross-match.
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The donor and recipient generally must be ABO compatible. This can occur under one of the following circumstances: the donor and recipient are ABO identical, the donor has blood type O (universal donor), or the recipient is blood type AB (universal recipient). Given the distribution of blood group antigens in the United States, the waiting time on the deceased donor list is prolonged for patients with blood group O and B. A recipient with blood type B and a low anti-A Ag IgG titer can potentially receive a transplant from a donor with blood type A2B or A2 (see Question 8).
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When a potential donor is identified, a cross-match is performed prior to transplantation to evaluate for any evidence of preformed antibodies against the specific donor (human leukocyte antigens [HLA]) that could result in hyperacute and/or acute humoral rejection. A final cross-match using fresh serum is performed in all cases immediately preceding transplantation to ensure compatibility between the donor and recipient. The methods available for cross-match testing include: enzyme-linked immunosorbent assay, flow cytometry, complement-dependent cytotoxicity, and single antigen bead assay. Transplantation has been done with low-level pre-existing donor specific antibody (DSA); however, graft function tends to worsen quicker than in those without pre-existing DSA.
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If the donor is incompatible with the recipient, then Kidney Paired Donor Exchange is the most common solution today; we will discuss this further in the next question. ABO-incompatible or cross-match positive transplantations following desensitization strategies have been performed successfully at some institutions.
7. What is kidney paired donor exchange?
Barriers against living kidney donation include ABO blood group incompatibility and existence of preexisting HLA antibodies between potential donor-recipient pairs. In a Kidney Paired Donor Exchange (KPDE) program, a medically approved incompatible pair is able to receive and exchange with other incompatible pair(s). This results in compatible organs for all recipients. The first KPDE was established in the United States in 2000. There were a total of 552 kidneys transplanted in 2014 with the KPDE program, amounting to about 10% of all living donor transplants that year.
The five different types of exchange include:
- 1.
Two-way is between two incompatible pairs with the procurement operations occurring simultaneously so that neither donor could back out.
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k -Way ( k is the number of pairs) is exchanges between more than two pairs using the same concept of the two-way exchange. Reciprocally matching donors are not required. For example, Pairs A, B, and C, Pair A donor is compatible with Pair B recipient, but Pair B donor is not a match for the Pair A recipient. However, Pair C donor is a match for Pair A recipient and Pair C recipient is a match for Pair B donor. Now all three recipients receive a transplant from a compatible donor. Due to logistical reasons of the donors required to be in the operating room at the same time, the number in this exchange is usually limited to 3 to 4 pairs.
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Unspecified donor chain starts with an unspecified donor (altruistic donor), who, instead of, as previously, donating to the deceased donor list, would now donate to an incompatible pair. The donor in this incompatible pair would donate to another incompatible pair and this pattern would continue, forming a chain. The last donor in the chain would donate to the deceased donor list, ending the chain. This modality of donor exchange is called the domino-paired donation (DPD). Since it is possible to arrange these chains so that no donor-recipient pair had to donate a kidney before receiving a kidney, the requirement for all donors to be in the operating room simultaneously was relaxed. This allowed for the development of the non-simultaneous extended altruistic donor chains. The last donor in a DPD would become a “bridge” donor, which meant instead of donating to the deceased donor list, the donor would donate to another incompatible pair at a later time, thus extending the chain.
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List exchange is when a donor in an incompatible pair donates to the deceased donor list and their recipient is now given priority for a deceased donor organ transplant.
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Altruistically unbalanced exchange is between a compatible pair and another incompatible pair. It allows an incompatible pair to find a donor and affords the opportunity for the compatible pair to receive a kidney of higher quality.
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