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How Small Is Too Small and How Young Is Too Young When Allocating Pediatric Deceased Donor Kidneys to Optimize Kidney Transplant Rates?

Adams, Megan A. MD1; Bock, Margret E. MD2; Goebel, Jens MD2

doi: 10.1097/TP.0000000000002705
Commentaries
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1 Division of Transplant Surgery, Children’s Hospital Colorado, University of Colorado, Aurora, CO.

2 Division of Pediatric Nephrology, Children’s Hospital Colorado, University of Colorado, Aurora, CO.

Received 19 February 2019.

Accepted 23 February 2019.

M.A. and M.B. contributed equally to this commentary by reviewing and editing it (M.A. from a transplant surgical and M.B. from a pediatric medical perspective).

J.G. drafted and then finalized the commentary after receiving M.A.’s and M.B.’s input.

The authors declare no conflicts of interest.

Correspondence: Jens Goebel, MD, Division of Pediatric Nephrology, Children’s Hospital Colorado, 13123 East 16th Avenue, 328, Aurora, CO 80045. (jens.goebel@childrenscolorado.org).

In this issue of the journal, Suneja et al1 present a very informative analysis of the usage of small (donor age <8 y and weight <30 kg) pediatric deceased donor kidneys and associated outcomes in the United States. Not surprisingly given the relative scarcity of pediatric donors (and recipients), some of their findings and conclusions are not entirely firm from a statistical perspective. That being said, several important threads emerge from this article:

  1. Small pediatric deceased donor kidneys are underutilized.
  2. Many small pediatric deceased donor kidneys do not need to be transplanted en bloc but can be used as single grafts.
  3. Small pediatric deceased donor kidneys should ideally be allocated to centers where there is expertise with the use of such organs.
  4. Small pediatric deceased donor kidneys can be used successfully for many, but probably not for very young and very small, pediatric recipients.

Suneja et al, looking at donor utilization and transplant rates in the United States over the 10-year period between 2005 and 2014, show that the use of kidney donors weighing <25 kg was disappointingly and unnecessarily low in that time period. While potential kidney donors weighing between 25 and 29.9 kg were used >90% of the time and thus at rates comparable to adult donors, usage rates for smaller donors were substantially lower, for example, just over 50% for donors weighing 10–14.9 kg. When used, however, kidneys from these donors weighing 10–14.9 kg worked very well, even if they were transplanted as single kidneys and not en bloc. These quite favorable outcomes of transplants performed using single kidneys from small pediatric deceased donors validates the recently approved policy by United Network for Organ Sharing mandating the use of split, rather than en bloc, kidneys from deceased donors weighing at least 18 kg.2

Suneja et al appropriately point out that the very good outcomes they observed using small pediatric deceased donor—as long as donor weight was at least 10 kg—kidneys, even when used as single kidneys and not en bloc, may be related to the selective procurement and use of these organs for transplantation at centers where there is surgical and programmatic expertise in and comfort with such transplants. While verification and quantification of such a phenomenon exceed the scope of the work done by the authors, their findings suggest that consistently procuring single kidneys from donors weighing at least 10 kg and using them at centers with experience in transplanting such small kidneys would result not only in more overall transplants but also in more successful transplants. Regulatory oversight (eg, by United Network for Organ Sharing in the United States) should accordingly be updated to facilitate this and thus increase the number of successful kidney transplants.

Historically, and as mentioned by Suneja et al, transplanting small pediatric deceased donor kidneys into pediatric recipients has been frowned upon to some extent, mostly because of concerns related to vascular thrombosis and stenosis and urologic complications.3 The authors’ findings re-emphasize and extend prior data,4–6 suggesting that this philosophy should be reevaluated for many (at least school age and size based on current data) pediatric candidates. Of note, Suneja et al’s data understandably lack the statistical power to conclusively mandate such a reevaluation, even though they used a large national database for their study. As is the case with many things in pediatric transplantation, acquiring the numbers needed to prove or disprove certain matters using conventional scientific and statistical standards will likely take a very long time, or, realistically, may never be achievable.

Finally, we believe that 2 additional and partially related questions would be interesting to explore: first, do these good outcomes described by Suneja et al exist equally with both small pediatric brain dead donors and with small pediatric donation after circulatory death (DCD) donors? In the United States, organs from DCD donors with high kidney donor profile indices at either end of the extremes of donor age are often discarded. Even though the numbers would likely be quite small as alluded to above, it would be interesting to specifically know the outcomes of small pediatric donor kidneys procured by DCD. Second, is there a graft size-to-recipient weight ratio that could be deduced and applied to optimally match small pediatric donor kidneys and pediatric recipients? In other words, what actually is a reasonably safe small recipient size when using these kidneys?

Perhaps a push to routinely procure small pediatric donor kidneys and allocate them to centers comfortable with and experienced in their use, paired with diligent monitoring and regular review of such an approach and its associated outcomes, should therefore be one of our goals going forward. This would further enhance our efforts to maximize successful kidney transplants for the ever-growing number of patients with end-stage renal disease, including children, who we are so passionate to serve.

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REFERENCES

1. Suneja M, Kuppachi S, Katz D, et al. Small split pediatric kidneys to expand the donor pool: an analysis of Scientific Registry of Transplant Recipients (SRTR) data.TransplantationIn press
2. Organ Procurement and Transplantation NetworkImproving en bloc kidney allocation 2.2017US Department of Health and Human Services websiteAvailable at https://optn.transplant.hrsa.gov/governance/public-comment/improving-en-bloc-kidney-allocation-2. Accessed February 7, 2019
3. Singh A, Stablein D, Tejani A. Risk factors for vascular thrombosis in pediatric renal transplantation: a special report of the North American pediatric renal transplant cooperative study.Transplantation1997631263–1267
4. Sui M, Zhao W, Chen Y, et al. Optimizing the utilization of kidneys from small pediatric deceased donors under 15kg by choosing pediatric recipients.Pediatr Transplant20162039–43
5. Wang HY, Li J, Liu LS, et al. En bloc kidney transplantation from infant donors younger than 10 months into pediatric recipients.Pediatr Transplant201721e12845
6. Winnicki E, Dharmar M, Tancredi D, et al. Comparable survival of en bloc versus standard donor kidney transplants in children.J Pediatr2016173169–174
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