*Purpose: Kidneys from very young pediatric donors continue to be underutilized due to concerns for technical complications and hyperfiltration injury. The decision to transplant these kidneys individually or as a pair remains controversial. In order to investigate this in more detail, we compared outcomes in adult pediatric kidney transplant (PKT) recipients receiving en bloc and solitary kidneys.

*Methods: Between 2007 and 2018, 51 adult PKT recipients from donors weighing <20 kg were identified at Mayo Clinic Arizona. 36 adult recipients received en bloc PKT; 15 received a solitary PKT. Results were analyzed using chi-square, unequal variance t-tests and Kaplan-Meier survival analysis.

*Results: In comparing en bloc and solitary PKT groups, no differences were observed in recipient age (p=0.1512) or BMI (p=0.2161). Recipient weight was lower in the solitary PKT group (58.9±7.8vs. 69.7±12.7, p=0.0037). No differences were observed in donor age (p=0.3780), weight (p=0.1931), BMI (p=0.6116) or KDPI score (p=0.3814). No differences were observed in measured donor kidney length (right, p=0.4829; left, p=0.918). eGFR was lower in the solitary PKT group at 4 months (p=0.0016), 1 year (p=0.0318) and 2 years (p=0.0066) (Figure 1). No differences in proteinuria were observed between groups at 1 month, 4 months, 1 year and 2 years (p=0.9324). No significant chronic tubulointerstitial damage was appreciated at 4 months and 1 year by protocol biopsy. No differences were observed in patient (100.0% vs. 100.0%, p>0.9999) or allograft survival (94.4% vs. 93.3%, p>0.9999) at 1 year when comparing en bloc and solitary PKT.

*Conclusions: Good outcomes can be achieved using solitary PKT with appropriate donor-recipient pairing although the differences observed between donor renal mass and recipient body mass are not inconsequential. A lower, albeit satisfactory eGFR, was observed in solitary PKT recipients at 1 and 2 years post-transplant. Lack of proteinuria and biopsy changes supporting hyperfiltration injury suggest that this finding is due to ongoing renal mass-recipient volume mismatch. When deciding on how to best use PKT, the balance of maximizing organ utilization and recipient outcomes should be carefully weighed.

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