*Purpose: The objective of this study is to compare graft outcomes for patients with pre-transplant elevated plasma oxalate (Pox) compared to a matched cohort.

*Methods: Kidney transplant recipients between 2003 to 2021 with elevated plasma oxalate levels (Pox) at the time of kidney transplant evaluation were included. Primary hyperoxaluria cases were excluded. A matched control cohort in a 2:1 ratio of controls to cases using patient/donor age, living/deceased donor type, PRA, KDPI, and HLA mismatch as matching variables. Patient characteristics and transplant outcomes were gathered for both cohorts.

*Results: A total of 107 patients with elevated POx (cases) were identified and 214 controls. The most common enteric cause was Roux-en-Y gastric bypass (RYGB, 37.4%) and 33.6% of patients did not have an identified cause. Compared to controls, cases had higher prevalence of pre-transplant nephrolithiasis (52.3% vs 26.9%, p=0.0001) and lower rates of hypertension (83.2% vs 89.4%, p=0.01). Median pre-transplant POx was 11.9 (min 1.9, max 68mcmol/l). Only 11% had Pox >30mcmol/l pre-transplant. POx cases were more likely to have calcium oxalate crystals reported on allograft biopsy compared to controls (6.7% vs 1.1%, p=0.009). At 1 year, mean eGFR was 50.0(SD=21.4) in cases compared to 52.4(SD=15.6) in controls. Across stages of eGFR, POx cases had higher rates of eGFR between 15-29 (15% vs 3.4%), and lower rates of eGFR between 45-59 (22.5% vs 33.7%), p=0.007 (Table 1). This pattern persisted for eGFR at last followup but was not statistically significant (p=0.09).

*Conclusions: Despite low mean POx levels prior to kidney transplant, cases with an elevated POx had lower rates of eGFR between 45-59ml/min and higher rates of eGFR between 15-29ml/min at 1 year post transplant compared to a matched cohort. Studies with longer follow-up are needed to characterize if pre-transplant oxalosis adversely impacts short and long term graft function.

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