*Purpose: An appropriate assessment of donor organ quality is crucial to optimize the kidney allocation and improve the long-term outcomes. Kidney Donor Risk Index (KDRI), a non-invasive evaluation of donor kidneys quality was implemented in some transplant centres, but its relationship with early post-transplant chronic histologic changes remains unknown. The aim of this study was to analyse the correlation between KDRI, histopathological parameters in the early post-transplant renal biopsy and graft function.

*Methods: Among 732 patients, transplanted between 2015 and 2021, we identified 353 first cadaveric kidney graft recipients who underwent early protocol core needle biopsy (on average 12±5.5 days after transplantation). Histological evaluation was based on the Banff classification. Kidney graft function was analysed as MDRD eGFR evaluated at 3, 6 and 12 months after transplantation. KDRI was calculated retrospectively according to formula proposed by Rao and patients were divided into quartiles of KDRI values.

*Results: The median KDRI in our cohort was 1.23 (IQR, 0.96-1.46). In the recipients of kidneys with the highest KDRI quartile there was greater proportion of glomerular sclerosis (9.8±13.1% vs. 1.4±3.2%, p<0.001) and higher Banff scores for interstitial fibrosis (ci; 0.75±0.77 vs. 0.19±0.43, p<0.001), vascular intimal thickening (cv; 0.45±0.82 vs. 0.20±0.59, p<0.05), arteriolar hyalinosis (ah; 0.84±0.93 vs. 0.30±0.59, p<0.001) and tubular atrophy (ct; 0.99±0.66 vs. 0.67±0.56, p<0.005) as compared to the lowest KDRI quartile kidneys. Recipients of kidneys with high KDRI were older (59±12 vs. 46±12 years, Q IV vs. I respectively, p<0.001). The mean eGFR at 12 months after transplantation was significantly lower in the highest KDRI quartile compared to the lowest one (43.8±15.4 vs. 65.5±17.8 µmol/l respectively, p<0.001). A significant positive correlation was found between KDRI and eGFR at 12 and 18 months post-transplant (r=0.31, p<0.001 and r=0.39, p<0.001, respectively). Moreover, we noted a significant positive correlation between KDRI values and both chronic histological changes (ci+ct+cv+ah) as well as % of sclerosed glomeruli in reviewed biopsies (r=0.33, p<0.001 and r=0.35, p<0.001, respectively).

*Conclusions: The KDRI value correlates with the degree of early histopathological changes of the transplanted kidney and post-transplant graft function. Routine calculation of KDRI may help predict kidney graft function and improve donor-recipient matching in Poland.

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