Intermediate Renal Outcomes, Kidney Failure, and Mortality in Obese Kidney Donors

A Single-Center Retrospective Study to Identify Causes of Sex Differences in the Living Kidney Donor Evaluation Process

Key Points

Background

Multiple studies have shown that female volunteers are living donors (LDs) for kidney transplantation at higher rates than male volunteers. However, the underlying reasons for this observation are not well understood. We examined the LD evaluation process to determine the point at which sex imbalance arises. On the basis of a previous study, we hypothesized that both sexes are equally likely to become approved as LDs, but female volunteers are more likely to follow through with donation.

Methods

This is a single-institution retrospective chart review of self-referrals for LD evaluation between January 2009 and December 2022. Self-referrals were identified using the Organ Transplant Tracking Record database and cross-referenced with billing data. Exclusion at each stage of evaluation was recorded and compared between sexes using log binomial regression; unadjusted and adjusted (for donor age, race, ethnicity, relationship to recipient, and recipient sex) risk ratios with 95% confidence interval were determined.

Results

One thousand eight hundred sixty-one self-referrals were reviewed, including 1214 female (65.2%) and 647 male (34.8%) volunteers, resulting in 146 approvals and 125 donations (76/125, 60.8% female, 49/125, 39.2% male). Adjusted risk ratios indicated no significant differences between sexes in completing medical and/or psychosocial workup, having medical and/or psychosocial contraindications, being approved for donation, and proceeding with donation. The top medical contraindications for both sexes were obesity, hypertension, and nephrolithiasis.

Conclusions

Female overrepresentation among LDs is likely due to the 1.9 times higher rate of self-referral for evaluation. After this point, both sexes were equally likely to complete workup, be approved, and follow through with donation. Increased efforts to engage male volunteers at the initial self-referral stage has the potential to expand access to LD kidney transplantation.

Podcast

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Change in Body Mass Index and Attributable Risk of New-Onset Hypertension Among Obese Living Kidney Donors

OBJECTIVE

To examine whether body mass index (BMI) changes modify the association between kidney donation and incident hypertension.

BACKGROUND

Obesity increases hypertension risk in both general and living kidney donor (LKD) populations. Donation-attributable risk in the context of obesity, and whether weight change modifies that risk, is unknown.

METHODS

Nested case-control study among 1558 adult LKDs (1976-2020) with obesity (median follow-up: 3.6 years; interquartile range: 2.0-9.4) and 3783 adults with obesity in the Coronary Artery Risk Development in Young Adults (CARDIA) and Atherosclerosis Risk in Communities (ARIC) studies (9.2 y; interquartile range: 5.3-15.8). Hypertension incidence was compared by donor status using conditional logistic regression, with BMI change investigated for effect modification.

RESULTS

Overall, LKDs and nondonors had similar hypertension incidence [incidence rate ratio (IRR): 1.16, 95% confidence interval (95% CI): 0.94-1.43, P =0.16], even after adjusting for BMI change (IRR: 1.25, 95% CI: 0.99-1.58, P =0.05). Although LKDs and nondonors who lost >5% BMI had comparable hypertension incidence (IRR: 0.78, 95% CI: 0.46-1.34, P =0.36), there was a significant interaction between donor and >5% BMI gain (multiplicative interaction IRR: 1.62, 95% CI: 1.15-2.29, P =0.006; relative excess risk due to interaction: 0.90, 95% CI: 0.24-1.56, P =0.007), such that LKDs who gained weight had higher hypertension incidence than similar nondonors (IRR: 1.83, 95% CI: 1.32-2.53, P <0.001).

CONCLUSIONS

Overall, LKDs and nondonors with obesity had similar hypertension incidence. Weight stability and loss were associated with similar hypertension incidence by donor status. However, LKDs who gained >5% saw increased hypertension incidence versus similar nondonors, providing support for counseling potential LKDs with obesity on weight management postdonation.

Long-Term Kidney and Maternal Outcomes After Pregnancy in Living Kidney Donors

For counseling it is important to know if pregnancy after Living Kidney Donation (LKD) affects long-term outcomes of the mono-kidney and the mother. Therefore, we performed a retrospective multicenter study in women ≤45 years who donated their kidney between 1981 and 2017. Data was collected via questionnaires and medical records. eGFR of women with post-LKD pregnancies were compared to women with pre-LKD pregnancies or nulliparous. eGFR before and after pregnancy were compared in women with post-LKD pregnancies. Pregnancy outcomes post-LKD were compared with pre-LKD pregnancy outcomes. 234 women (499 pregnancies) were included, of which 20 with pre- and post-LKD pregnancies (68) and 26 with only post-LKD pregnancies (59). Multilevel analysis demonstrated that eGFR was not different between women with and without post-LKD pregnancies (p = 0.23). Furthermore, eGFR was not different before and after post-LKD pregnancy (p = 0.13). More hypertensive disorders of pregnancy (HDP) occurred in post-LKD pregnancies (p = 0.002). Adverse fetal outcomes did not differ. We conclude that, despite a higher incidence of HDP, eGFR was not affected by post-LKD pregnancy. In line with previous studies, we found an increased risk for HDP after LKD without affecting fetal outcome. Therefore, a pregnancy wish alone should not be a reason to exclude women for LKD.

Diabetes-free survival among living kidney donors and non-donors with obesity: A longitudinal cohort study

BACKGROUND

Approval of living kidney donors (LKD) with end-stage kidney disease (ESKD) risk factors, such as obesity, has increased. While lifetime ESKD development data are lacking, the study of intermediate outcomes such as diabetes is critical for LKD safety. Donation-attributable diabetes risk among persons with obesity remains unknown. The purpose of this study was to evaluate 10-year diabetes-free survival among LKDs and non-donors with obesity.

METHODS

This longitudinal cohort study identified adult, LKDs (1976-2020) from 42 US transplant centers and non-donors from the Coronary Artery Risk Development in Young Adults (1985-1986) and the Atherosclerosis Risk in Communities (1987-1989) studies with body mass index ≥30 kg/m2. LKDs were matched to non-donors on baseline characteristics (age, sex, race, body mass index, systolic and diastolic blood pressure) plus diabetes-specific risk factors (family history of diabetes, impaired fasting glucose, smoking history). Accelerated failure time models were utilized to evaluate 10-year diabetes-free survival.

FINDINGS

Among 3464 participants, 1119 (32%) were LKDs and 2345 (68%) were non-donors. After matching on baseline characteristics plus diabetes-specific risk factors, 4% (7/165) LKDs and 9% (15/165) non-donors developed diabetes (median follow-up time 8.5 (IQR: 5.6-10.0) and 9.1 (IQR: 5.9-10.0) years, respectively). While not significant, LKDs were estimated to live diabetes-free 2 times longer than non-donors (estimate 1.91; 95% CI: 0.79-4.64, p = 0.15).

CONCLUSIONS

LKDs with obesity trended toward living longer diabetes-free than non-donors with obesity, suggesting within the decade following donation there was no increased diabetes risk among LKDs. Further work is needed to evaluate donation-attributable diabetes risk long-term.