Should Retrieved Kidneys Ever Be Discarded?

The worldwide shortage of deceased (cadaveric) donors focuses attention on donation rates, in particular on those countries which appear to be “doing well,” and on a wide range of proposals aimed at increasing the donor rate. These range from the legal framework and the donor coordinator system to the value of donor (or nondonor) registries. It is less well recognized that a high donor rate does not always equate to a similarly high transplant rate, such that not all organs that are donated and retrieved are necessarily transplanted. For many years the Council of Europe Transplant newsletter has published annual data on organ donation and transplant activity, initially from a limited number of European countries, more recently from a total of 55 countries across Europe, North and South America, and Australasia. These are the most reliable data currently available that allow international comparisons to be made. The most recent newsletter (1) contains data for 2004 that demonstrate the continuing development of transplantation in countries in Eastern Europe and South America, but it is the data from western European countries and the United States that are of particular interest. For example, the proportion of all donors that are multiorgan donors ranges from 53% to 96%. For deceased donor kidney transplantation (on the simplistic assumption that every donor has two transplantable kidneys), the percentage of available kidneys that are actually transplanted after donation appears to range from 65% in the United States and 69% in Spain to 96% in the Czech Republic and 94% in Norway and Austria. There is no clear trend that associates donor rates with kidney usage. This wide variation between different countries raises a number of questions. Are kidneys being removed in some countries that are not suitable for transplantation? Are kidneys being discarded after removal that could and should be used? Are kidneys being transplanted inappropriately? It is not possible from the registry data to answer these questions but an important analysis of some of the factors involved in discarding retrieved kidneys is presented in the paper by Cecka et al. (2). They compare practice in the United States with the Eurotransplant countries (Netherlands, Belgium, Luxembourg, Germany, Austria, and Slovenia) and show, using a slightly different data set and definitions from those quoted above, that 14% of retrieved kidneys are discarded in the United States compared with 5% in Eurotransplant. This difference is particularly marked as donor age increases, with 55% of kidneys from donors over 65 discarded in the United States compared with 12% in Eurotransplant. These differences would appear to result—in whole or part—from two systematic differences: The decision to discard kidneys in the United States is frequently based on biopsy findings, and 85% of kidneys from donors aged over 65 years were biopsied. Biopsy of kidneys in Eurotransplant was rare. The evidence base that is quoted in Cecka's paper for decision making after biopsy is remarkably thin—the cutoff threshold of less than 20% sclerosed glomeruli appears to be based largely on a report of eight biopsied kidneys (3), and there is clear evidence that wedge biopsy, which samples mainly the subcapsular glomeruli, is not representative of the entire cortex (4). Clearly more information on the interpretation and significance of donor biopsy is needed. In response to the inferior transplant outcome associated with the use of kidneys from older donors, Eurotransplant introduced the Eurotransplant Seniors Programme (ESP) in 1999 (5), which is an allocation scheme for kidneys from donors over the age of 65 years that gives priority to local recipients over the age of 65 years according to their waiting time only. HLA matching is ignored and every effort is made to minimize cold ischemic time. Experience to date of the scheme suggests that short- to medium-term outcomes in the ESP where biopsy data is not available are comparable to U.S. results for older kidney donor transplants (6). The recent (2002) modification to the U.S. allocation algorithm for “expanded criteria donor” kidneys has not reduced the discard rate. The unanswered question is whether the kidneys that are being discarded in the United States (over 1,500 per year), and probably elsewhere, would produce acceptable graft function and survival rates if transplanted. From the patient perspective a crucial observation is that in general transplantation with a “marginal” kidney is associated with a significant survival benefit when compared with dialysis (7), although this analysis used a somewhat different definition of a “marginal” kidney that did not include biopsy findings and used a lower age limit of 55 years to define “older” donors. A specific analysis based on donor age bands up to and over 65 years of age would be interesting. It may be important to accept that an inferior transplant outcome, when compared to the use of “ideal” donor kidneys, may look bad for the unit but may be highly acceptable to selected potential recipients—any analysis of unit results must be sufficiently sensitive to acknowledge this. If more kidneys from older donors are to be transplanted it is important to have an allocation process that selects suitable recipients. The ESP uses an age cutoff of 65 years. An alternative approach used in the U.K. allocation algorithm since 1998 (8), which will be extended in the new scheme expected to be introduced on 3 April 2006, is to incorporate age difference between donor and recipient into a point-scoring scheme (in a way that minimizes the age difference) as one of a number of factors. Thus kidneys from older donors are more likely to be offered to older recipients, but not exclusively so. As more information becomes available on the assessment of donated kidneys (9), it must be hoped that this valuable resource will not be discarded without clear evidence that these kidneys should not be transplanted.