*Purpose: The predictive ability of implantation biopsies of kidney allografts on either future recipient or living donor kidney function has not been fully elucidated. Herein, we report a single center preliminary experience with zero hour biopsies (ZHB) in living donor kidney transplants.

*Methods: All adult living kidney donors (LKD) and their intended recipients between March 2017 and November 2018 were analyzed. LKD underwent thorough medical evaluation including a 24 hour creatinine clearance (24CrCl) &gt80 ml/min/m². Allografts had pre-implantation multifocal needle core ZHB; tissue was fixed and embedded in routine manner. Histology findings were reported as either high risk (HR) or low risk (LR) based on presence of chronic changes such as moderate arteriosclerosis (AS) and/or &gt10% glomerulosclerosis (GS) in either biopsy. Kidney function was examined serially in both donor and recipients via serum creatinine (Cr) and estimated glomerular filtration rate (eGFR).

*Results: We identified 36 LKD allografts in which ZHB were performed: 19 were low risk (LR) and 17 were HR. Both groups had similar mean age (LR: 45±11 vs. HR: 50±9; p=0.20), females (LR: 78% vs. HR: 76%; p=ns), Caucasians (LR: 89% vs HR: 94%; p=ns). There was no significant difference between pre-donation creatinine (LR: 0.8±0.1 vs. HR: 0.9±0.1; p=0.39), eGFR (LR: 100±14 vs. HR: 92±14; p=0.13) and 24CrCl (LR: 133±44 vs. 116±23; p=0.14). HR ZHB had higher mean % GS in upper pole sample (LR: 2±3% vs. HR: 7±5%; p&lt0.001). Regarding vascular changes, HR cohort had 9 (53%) with moderate AS and 3 (18%) cases showing severe AS. This contrasts with LR ZHB noting mild AS in 47% of cases. To date, recipient and graft survival are 100% with no delayed graft function. Recipients of both ZHB cohorts had similar eGFR at six months follow up (LR: 61±14 vs. HR: 57±17; p=0.47). In addition, follow-up LKD eGFR was similar at one month (LR: 65±11 vs. HR: 58±15; p=0.16) and six months post-donation (LR: 66±15 vs. HR: 61±17; p=0.36). Most importantly, at six months of follow up, there was no difference in the number of donors with eGFR &lt60(LR: 26% vs. HR: 41%).

*Conclusions: Our preliminary data suggest that nearly 50% of LKD present unexpected chronic kidney pathology, unforeseen by standard LKD selection practices. Fortunately, the early analysis suggests these findings do not correlate clinically with donor or recipient kidney function during the first six months. However, HR ZHB donors could benefit from extended monitoring (beyond two years) as they may face increased risk of future kidney function deterioration.

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