LAUSR

In this issue of Liver Transplantation, Ekser et al. report the outcomes of combined liver-kidney transplantation (CLKT) recipients who had delayed implantation, a mean of 50 hours, of the kidney. This approach to dual organ transplantation is very thoughtful because it takes into consideration the changing physiology of the liver transplant recipient as hepatic function is restored. It also accounts for the unique and disparate needs of both organs when they are initially implanted. The approach advocated for by Ekser et al. improves the utility of both of the transplanted organs because allograft loss and patient death are minimized. Although this hypothesis-generating work is exciting, it is important to place it in the proper context, both in terms of its ability to be generalized into practice, as well as its potential implications on organ allocation. From a study design perspective, this study, similar to all retrospective single-center studies, is victim to unintended bias and confounding effects. The authors forthrightly acknowledge this in their discussion. Although this does not minimize the value of their observations, the reader should be informed about where bias exists. The study occurred over 12 years and although the authors address the possible influence of staff changes and surgical technique differences, the changes in recipient and donor selection criteria that may have occurred over that time are not captured in standard Scientific Registry of Transplant Recipients data reports. Additionally, the authors do not report on the outcomes of recipients who were intended to have a CLKT but were ultimately too ill to receive the kidney. This is of particular relevance in the delayed transplant cohort because the intervening time between the liver and kidney transplant allows the recipient to declare themselves in respect to outcome. If individuals were doing poorly was the kidney allograft still implanted? If not, might this account for the high patient and allograft survivals in this group of recipients? A provocative finding of this study is that in the delayed transplantation group, despite a mean cold ischemia time of 50 hours, pulsatile perfusion eliminated delayed graft function (DGF) by both the standard definition, dialysis required in the first 7 days after transplantation, as well as the less restrictive urine output definition. This finding, should it be validated, could change current practices. Hypothermic pulsatile perfusion (PP) use to reduce DGF in standard criteria donor kidneys, extended criteria donor kidneys, and kidneys from donation after circulatory death demonstrates that although PP significantly reduces the rate of DGF, it still occurs in 20% or more of allografts. However, these studies all examined significantly shorter cold ischemia times. In the sentinel article by Moers et al., the median cold ischemia time was 15 hours. In this randomized trial, the rate of DGF in the hypothermic machine perfusion cohort was 21%. There had been no studies examining the outcomes of transplanting kidneys with utilization of PP at a mean of 50 hours of cold ischemia time until now. This observation leads to 1 of 3 conclusions. Hypothermic PP for a longer duration has a protective or regenerative effect on the hypothermic ex vivo kidney. The physiologic milieu of a recently transplanted liver has a protective effect on the transplanted kidney, or the liver recipient had enough residual renal function or had begun to recover native renal function and did not need a kidney transplant. It is beyond the scope of this commentary to explore the first 2 scenarios. Certainly, were the first to be true, it would have a significant and positive impact on deceased donor kidney transplantation. However, in this case, the third scenario is most likely. In a retrospective single-center study, it has Abbreviations: CLKT, combined liver-kidney transplantation; DGF, delayed graft function; KDPI, kidney donor profile index; KDRI, kidney donor risk index; LDRI, liver donor risk index; PP, pulsatile perfusion.