*Purpose: Kidneys are pumped for therapeutic (to mitigate deleterious effects of ischemia), practical (to facilitate transplant scheduling), and prognostic (to assess organ quality) purposes. Yet the association between pumping’s primary prognostic measure – renal resistance (RR) – and graft survival is not well characterized. To aid transplant decision-making, the “BARETO” (Biopsy, Anatomy, and Resistance Effects on Transplant Outcomes) study aims to quantify relationships between these prognostic measures and outcomes to improve kidney offer decision-making.

*Methods: A cohort of 16,484 solitary deceased donor kidney transplants from 2008-2012 with non-missing RR as reported to the OPTN registry was used for unadjusted (Kaplan-Meier; single-variable Cox) and adjusted all-cause graft survival analysis out to 10 years. Causal inference with RR as the exposure variable was performed 3 ways using Cox regression: propensity-weighted, multivariable regression, and doubly robust regression (DRR) to adjust for 10 donor and recipient confounders including donor KDPI and recipient EPTS.

*Results: 1/3 of kidneys were pumped. Most (90%) RR values ranged between 0.1 and 0.4 mmHg/mL/min. Survival analysis revealed an unequivocally significant (p<0.0001) association between RR and all-cause graft survival probability (Fig 1). RR was highly correlated with KDPI and donor sex. The graft failure hazard ratio for RR 0.3-0.4 vs. <0.2 (HR 1.39, 95% CI: 1.28, 1.50) was only partially attenuated after DRR risk-adjustment (HR 1.24, 95% CI: 1.14, 1.34) (Fig 2). Results suggest graft failure risk does not continue to rise for RR values above 0.3-0.4, although selection bias may influence the results.

*Conclusions: After rigorous statistical adjustment, RR was found to be independently associated with graft survival. However, the detrimental effect of higher RR appears to plateau, calling into question the use of arbitrary thresholds such as 0.4 for declining a kidney. Incorporating RR as a component of multifactorial prediction models (e.g., KDRI) has the potential to improve organ offer decision-making by tempering the impact of prognostic measures on the kidney discard rate.

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