Liver exchange in the U.S.?

 From  Liver Transplantation 24 677–686 2018 

Liver paired exchange: Can the liver emulate the kidney?
Ashish Mishra  Alexis Lo  Grace S. Lee  Benjamin Samstein  Peter S. Yoo Matthew H. Levine  David S. Goldberg  Abraham Shaked  Kim M. Olthoff Peter L. Abt

Abstract: Kidney paired exchange (KPE) constitutes 12% of all living donor kidney transplantations (LDKTs) in the United States. The success of KPE programs has prompted many in the liver transplant community to consider the possibility of liver paired exchange (LPE). Though the idea seems promising, the application has been limited to a handful of centers in Asia. In this article, we consider the indications, logistical issues, and ethics for establishing a LPE program in the United States with reference to the principles and advances developed from experience with KPE. 

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"The potential number of donor and recipient pairs that might be suitable for LPE in the United States is unknown and is dependent on numerous factors. However, the Asan Medical Center experience from South Korea provides some perspective; among 2182 LDLT patients, 26 involved LPE.3 In the United States, most donors selected for LPE will likely be those where the donor is appropriate to donate with regard to the usual anatomical, medical, and psychosocial dimensions, but for 1 reason or another not appropriate for his or her intended recipient. Centers that evaluate living liver donors follow a stepwise approach to determining eligibility for donation. Some donors are rejected early in the evaluation process for obesity or other comorbidities, age, or being psychosocially unfit to proceed with donation.16, 17 Those who pass the initial screening process are assessed further for blood type, liver volumes, and other anatomical considerations, as well as general medical and psychosocial concerns. The donors who are rejected at this stage in the evaluation are the ones who could be considered for LPE. It is estimated that 3.5%‐17.0% of donors are rejected for ABOi, 4.1%‐14.0% for inadequate hepatic mass to support the recipient, and 1.5%‐6.0% due to vascular or biliary anatomic variations.17-20 There is considerable variation of these estimates based on the order of tests and the screening processes used to evaluate potential donors based on transplant center‐specific donor criteria. These barriers to donation represent opportunities for a variety of exchanges between donor and recipient pairs, such that the total number of lives saved through LDLT could be increased."
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Examples of Potential LPE

In the following section, we provide some examples of potential LPE. If the history of KPE serves as a guide for the trajectory of LPE, the number of pairs involved, the indications for participation, and the complexity of exchanges are likely to increase (Fig. 2).

1. Two‐way swap: ABOi pair and a pair where the estimated weight of the donor lobe is inadequate for the intended recipient (Fig. 2A).
2. Three‐way swap: ABO compatible pair where the remnant volume is too small for the donor; ABOi donor to small child where the left lateral segment (LLS) is also too large for the child; and an ABOi pair (Fig. 2B).
3. Nondirected donor starts a chain (Fig. 2C).
4. Patient with familial amyloid polyneuropathy (FAP) receives a deceased donor organ or LDLT and starts a chain with a domino liver (Fig. 2D).