Eligibility of Living Kidney Donors with Kidney Stone Disease

Introduction: Guidelines recommend that patients with a self-reported history of kidney stones or stones on imaging during living kidney donor (LKD) evaluation undergo 24-hour urine stone risk testing. We examined eligibility decisions for LKD candidates at two high-volume academic transplant centers based on 24-hour urine testing and imaging findings. Methods: We identified potential LKDs with a self-reported history of kidney stones or stones identified on imaging, who underwent 24-hour urine collection. Patients who could not donate due to other medical conditions were excluded. Differences in characteristics of patients approved vs. rejected for donation were determined using t tests and chi-square tests, or non-parametric tests when appropriate. Results: In total, 105 candidates met study criteria, of whom 22 (21%) were rejected for donation. Candidates rejected for donation had higher urinary calcium excretion (p<0.001), supersaturation of calcium oxalate (p<0.001), and supersaturation of calcium phosphate (p=0.02). Thirty-four candidates repeated 24-hour urine analyses following dietary or medical interventions for stone prevention. Candidates approved for donation had an increase in urinary volume (p=0.045), reduction in urinary calcium excretion (p=0.02), reduction in urinary oxalate excretion (p=0.04), and reduction in supersaturations of calcium oxalate (p<0.001), calcium phosphate (p=0.004), and uric acid (p=0.004). Those rejected for donation had no statistically significant changes in urinary parameters. While those rejected for donation had more stones on imaging compared to those approved, this did not reach statistical significance (p=0.06). Conclusion: Overall, urinary risk factors for nephrolithiasis and improvement in them following dietary or medical management were associated with approval for donation.