Howard, Matthew R.

ABSTRACTPurposeThis study aimed to assess whether kidney stone burden and risk factors at the time of kidney donor evaluation were associated with a symptomatic stone event post‐donor evaluation.MethodsWe identified adults evaluated at Mayo Clinic (two sites) (2000–2011) for living kidney donation and had either a personal history or radiological evidence of kidney stone disease. We analyzed demographics, stone risk factors, stone number/size, and the committee's donation decision and reasons. A follow‐up survey (2022–2023) assessed post‐evaluation symptomatic kidney stones and related morbidity.ResultsAmong 412 potential donors with kidney stone disease, 258 donated, 75 did not donate due to kidney stones, and 79 did not donate for other reasons. Multivariable analysis showed that candidates not donating due to stones had higher body mass index (BMI), prior symptomatic kidney stones, multiple stones on imaging, bilateral kidney stones, and diameter of largest stone ≥3 mm. Of 147 who completed the survey, 26 (18%) had a symptomatic kidney stone post‐donor evaluation. Younger age (p = 0.031) and multiple stones on imaging (p = 0.02) were significant predictors of post‐evaluation symptomatic stones regardless of donation status (p = 0.41).ConclusionsStone burden on imaging and prior symptomatic stone events were associated with not donating. Younger age and stone burden on imaging were the primary risk factors for a symptomatic kidney stone event after donor evaluation.

ABSTRACT Background Serum cystatin C–based estimated glomerular filtration rate (eGFRcys) generally associates with clinical outcomes better than serum creatinine–based eGFR (eGFRcr) despite similar precision in estimating measured GFR (mGFR). We sought to determine whether the risk of adverse outcomes with eGFRcr or eGFRcys was via GFR alone or also via non-GFR determinants among kidney transplant recipients. Methods Consecutive adult kidney transplant recipients underwent a standardized GFR assessment during a routine follow-up clinic visit between 2011 and 2013. Patients were followed for graft failure or the composite outcome of cardiovascular (CV) events or mortality through 2020. The risk of these events by baseline mGFR, eGFRcr and eGFRcys was assessed unadjusted, adjusted for mGFR and adjusted for CV risk factors. Results There were 1135 recipients with a mean baseline mGFR of 55.6, eGFRcr of 54.8 and eGFRcys of 46.8 ml/min/1.73 m2 and a median follow-up of 6 years. Each 10 ml/min/1.73 m2 decrease in mGFR, eGFRcr or eGFRcys associated with graft failure [hazard ratio (HR) 1.79, 1.68 and 2.07, respectively; P < .001 for all) and CV events or mortality outcome (HR 1.28, 1.19 and 1.43, respectively; P < .001 for all). After adjusting for mGFR, eGFRcys associated with graft failure (HR 1.57, P < .001) and CV events or mortality (HR 1.49, P < .001), but eGFRcr did not associate with either. After further adjusting for CV risk factors, risk of these outcomes with lower eGFRcys was attenuated. Conclusion eGFRcr better represents the true relationship between GFR and outcomes after kidney transplantation because it has less non-GFR residual association. Cystatin C is better interpreted as a nonspecific prognostic biomarker than is eGFR in the kidney transplant setting.