The role of hypothermic machine perfusion in selecting renal grafts with advanced histological score

Background: Few studies explored the role of hypothermic machine perfusion (HMP) in the sub-group of non-standard renal grafts with a biopsy-proven advanced histological impairment. This study aimed to investigate the role of HMP in grafts with a Karpinski Score >3 in terms of the need for dialysis, creatinine reduction ratio at day-7 (CRR7), and 3-year graft survival. Methods: Twenty-three perfused grafts with Karpinski Score >3 evaluated between November 2017 and December 2018 were retrospectively analyzed and compared with a control group of 32 non-perfused grafts transplanted between January 2014 and October 2017. Results: After transplantation, perfused grafts had fewer cases requiring dialysis (8.7% vs. 34.4%; p = 0.051), a better reduction in serum creatinine (median at 7 days: 2.2 vs. 4.3 mg/dl; p = 0.045), and shorter length of hospital stay (median 11 vs. 15 days; p = 0.01). Three-year death-censored graft survival was better in the perfused cases (91.3% vs. 77.0%; p = 0.16). In perfused grafts, initial renal resistance (RR) had the best predictive value for renal function recovery after the first week, as defined by CRR7 ≤ 70% (AUC = 0.83; p = 0.02). A cut-off value of 0.5 mm Hg/ml/min showed a sensitivity of 82.4%, a specificity of 83.3%, and diagnostic odds ratio = 23.4. After dividing the entire population into a Low-RR (n = 8) and a High-RR Group (n = 15), more cases with CRR7 ≤ 70% were reported in the latter group (86.7 vs. 13.3%; p = 0.03). Conclusion: HMP yielded promising results in kidneys with Karpinski Score >3. Initial RR should be of interest in selecting non-standard organs for single kidney transplantation even in impaired histology.