While pressures to increase organ donation have begun to yield significant advances in recent years, US transplant centers continue to discard deceased donor kidneys that have been procured for transplantation at what appears to be an alarming rate. Between October 1999 and June 2005, more than 9000 donated kidneys were determined to be unsuitable for transplantation, including 41% (5139 of 12 536) of the expanded criteria donor (ECD) kidneys procured, according to an analysis from the Scientific Registry of Transplant Recipients in this issue (1). Morioka et al. have identified ‘biopsy results’ as a major reason for discard for ECD kidneys and use of pulsatile perfusion for kidney preservation as a mitigating factor.
The study again raises questions about the importance of the biopsy in evaluating ECD kidneys for transplantation. The authors found no correlation between the biopsy results and subsequent allograft survival when kidneys with similar degrees of glomerular sclerosis were transplanted. The authors are careful to caution that there may be important selection biases at work that cannot be detected in Registry analyses and that the degree of glomerulosclerosis is the only biopsy result that can be evaluated from the forms that are submitted. Unreported biopsy findings of arteriosclerosis or fibrosis certainly might also be considered in the decision not to use a kidney. But although biopsy results may be listed as the reason these kidneys are discarded at high rates, the real reason for not using more of these kidneys is far more complex.
The study notes that discard rates varied from 14% to 60% depending upon where the kidneys were procured, suggesting that local practices in different donor service areas play a much more important role in whether these kidneys are transplanted or not than whether a biopsy was performed or whether the kidney was placed on a pump. This probably results from several types of practices: over procurement of organs that local surgeons ultimately will find unsuitable for transplantation, larger waiting lists or patient mixes that allow more ECD kidneys to be placed locally or prior identification of a limited number of appropriate recipients willing to accept an ECD kidney.
The United Network for Organ Sharing instituted the current ECD allocation policy (3.5.8) in October 2002 that specifically allocates ECD kidneys to candidates willing to accept them with the goal of limiting the number of offers required to place the kidney and reducing cold ischemia times by streamlining placement. It was hoped that this policy would reduce waiting times for older patients, diabetics and those with limited vascular access in exchange for their willingness to accept a kidney with an increased risk of failure (2) and would encourage recovery and transplantation of these kidneys. Although the number of ECD kidneys procured and transplanted increased following the implementation of this policy, the proportion discarded did not change (3). Similarly, the goals of reduced waiting times and more rapid placement appear only to have been achieved at centers with fewer than 20% of their renal candidates listed for an ECD kidney (4).
The University of California at San Francisco (5) reported that by selecting ECD candidates according to specific recommendations (2), they reduced their biopsy rate of ECD kidneys by 85%. The incidence of delayed graft function fell from 43% to 15% and the cold ischemia times from 16 to 7 h on an average compared with historical controls. The authors concluded that the ECD designation, when appropriate recipients were selected, might obviate the need for biopsy. Many biopsies are performed to evaluate the suitability of an ECD kidney for a candidate who does not really fit the suggested eligibility requirements for ECD candidates. The result is a likely delay in placement, repeated declines of offers and an increase in cold ischemia time making a suboptimal kidney even less desirable and more prone to discard.
Similarly, the Eurotransplant Seniors Program, which preferentially offers kidneys from donors over age 65 to patients over age 65 who have consented to accept them resulted in a low discard rate of about 5% for these older donor kidneys (6). At the time of the study, pretransplant biopsies were rarely if ever performed on these kidneys.
Ideally, biopsies should be used to evaluate donors and not for recipient selection. In reality, this is a difficult distinction. There is a spectrum of risk among ECD donors and some may be appropriate for younger patients. Morioka et al. noted that ECD discard rates increased with age and comorbidities predisposing to increased risk of graft failure. Thus, a continuous donor-risk index rather than an ECD category may permit better selection of appropriate patients for riskier organs and facilitate their placement.
Ultimately, improved utilization will come from a better allocation system—one that matches donors and recipients for risk and opens geographic boundaries so that aggressive organ procurement agencies serving conservative transplant centers may share kidneys beyond their service areas in a timely manner. Where there are high rates of ECD discards it would certainly be worthwhile to scrutinize the practices that may limit utilization of this important resource.