Safety of Nephrectomy in Older Living Kidney Donors

Due to a shortage of organs for transplantation, it has become more common for transplanted kidneys to come from donors aged ≥70 years. However, the safety of nephrectomy in these older donors has not been well studied. Often, studies of extended criteria donors focus on living kidney donors (LKDs) 55 to 65 years of age because fewer living donors aged 70 years or older exist. One study that focused on LKDs ≥70 years found that postdonor nephrectomy survival was better for this group than heavily matched controls, but it did not demonstrate the safety of nephrectomy.

To address this knowledge gap, Takahisa Hiramitsu, MD, PhD, et al examined outcomes of living kidney donors aged ≥70 years after donor nephrectomy. Their findings were published in KI Reports.

Dr. Hiramitsu and colleagues enrolled 1226 LKDs and stratified them into age groups of 30 to 49 years (n=244), 50 to 69 years (n=803), and 70 to 89 years (n=179). For each group, respectively, 34.0% (83), 35.5% (285), and 44.7% (80) of participants were male. Researchers completed postoperative assessments at 1, 3, 6, and 12 months after transplantation, and annually thereafter. Follow-up was more frequent (every 1 to 3 months) if comorbidities were present.

The research team used the Kruskal-Wallis test for continuous variables and the chi-square test for categorical variables and confirmed normal distribution of estimated glomerular filtration rate (eGFR) data using histograms. They conducted a linear mixed model analysis to determine whether the LKD age groups affected eGFRs over time. Estimated marginal means and their standard errors and 95% CI were calculated and compared among the LKD groups at each time point. Researchers used the Benjamini-Hochberg method (a false discovery rate method) to adjust for multiple comparisons.

The reference standard for time was postoperative day (POD) 6, and the estimated mean and 95% CI of the difference (amount of change) relative to the eGFR on POD 6 were calculated and compared among age groups. Further analysis was performed using the same linear mixed model. For multivariate analysis, the research team developed a model with all variables (time, sex, and LKD age groups) using the forced entry method. They performed a survival analysis to determine whether LKD age groups influenced overall donor survival and determined the cumulative survival rate using the Kaplan-Meier method. P<.05 was considered significant in all analyses.

The research team compared surgical outcomes, postoperative eGFRs, end-stage renal disease (ESRD) incidences, and mortality rates among the different participant groups. Follow-up occurred from January 2008 through August 2022, with a median observation period of 73 months (interquartile range, 41-19 months).

Surgical outcomes, including graft quality and adverse events, were comparable among the three age groups. Among all three groups, eGFR changes were similar. The eGFRs of LKDs aged 30 to 49 and 70 to 89 years were the highest and lowest, respectively, among the three LKD age groups. The eGFR improved slightly for all groups after POD 6, but improvements were significantly lower in the group aged 70 to 89 years as indicated by the unadjusted (P=.009; estimate: −0.928; 95% CI, −1.624 to −0.231) and adjusted (P=.002; estimate: −1.074; 95% CI, −1.763 to −0.385) analyses. This group also had the highest mortality rate, although the authors noted that this may be considered acceptable given their advanced age. A total of 19 LKDs died of different causes. There was no ESRD observed in any group.

Limitations of the study include its retrospective nature, lack of comparison with a healthy population, and low incidence of events. These limitations warrant studies of a larger population with longer observation periods, according to the researchers.

The study authors concluded that donor nephrectomy is safe for LKDs aged ≥70 years. “Despite the low eGFR changes and improvement after donor nephrectomy, LKDs aged 70 years or older can maintain their kidney function without ESRD,” they wrote. “Regarding life expectancy, [living kidney donor transplants] involving LKDs aged 70 years or older are associated with favorable outcomes. The results of this study may aid in the discovery of optimal indications for preoperative eGFRs of LKDs and increase the number of eligible LKDs.”

Source: KI Reports