Background: Because of the increasing waiting time for kidney transplantation, transplant centers may feel pressured to liberalize living kidney donor selection criteria, as long as donor safety can be guaranteed. In this study, we report the most common reasons for declining potential living kidney donors. Furthermore, we compared characteristics of declined donors to accepted donors and investigated whether these changed over time.

Methods: We performed a singe-center cohort study in 1412 potential living kidney donors who were evaluated for donation between 1982 and 2018. Of these potential donors, 173 (12%) were declined. Reasons to decline donation were retrieved from the decision letter in the electronic patient record. We collected and compared demographic characteristics (age, sex, estimated  glomerular filtration rate (eGFR), weight, length, blood pressure) of declined and accepted donors. Trends over time in our center were assessed using univariable linear reression analysis in both declined and accepted donors.

Results: Most common reasons to decline a donor were renal artery calcification (and accompanying stenosis) (N=41, 24%), low eGFR (N=40, 23%), obesity (N=19, 11%) and and suspicion of a malignancy (N=13, 8%). Mean±SD age was 60±11 years in the declined donors vs. 52±10 years in the accepted donors (P<0.001). Sex did not differ significantly between the groups (58% female in the declined vs. 54% in the accepted group, P=0.39). Estimated GFR was significantly lower in the declined group than the accepted group (81±14 mL/min/1.73m² vs. 91±13 mL/min/1.73m² respectively, P<0.001). Systolic blood pressure was significantly higher in the declined group, compared to the accepted group (131±14 mmHg vs. 128±14 mmHg respectively, P=0.02). In the declined group, 27% individuals used antihypertensive medication vs. 14% in the accepted group (P<0.001). Over time, eGFR became lower in the declined donors and BMI increased (St.β=-0.18, P=0.02 and St.β=0.16, P=0.04 respectively), while these variables did not change in the accepted donors.

Conclusions: We show that in our center, renal artery calcification and low pre-donation eGFR are the most common reasons to decline potential living kidney donors. Declined donors were older, had higher blood pressure and lower eGFR, compared to accepted donors, and these differences increased over time. These findings inform the evaluation of living donor selection criteria. Better understanding of the long-term course and impact of renal artery calcification is needed to conclude on the validity of this reason.