Comparative Analysis Between Pediatric and Adult Kidney Transplant Recipients: a Multicentric Retrospective Study

Achieving long-term graft survival with minimal patient morbidity are key goals in kidney transplantation (KT). However, clinical and biological factors differ significantly between pediatric and adult populations. Pediatric patients experience immune system maturation, affecting alloimmune responses and immunosuppression efficacy, and higher immune reactivity whereas adults are more prone to immune dysregulation and comorbidities. Despite these differences, pediatric treatment protocols are largely adapted from adult guidelines, with limited direct comparative studies. Therefore, we conducted a multicenter retrospective study comparing the outcomes of pediatric and adult kidney transplant recipients (KTR).

Subjects who received KT between Jan 1, 2017 and Dec 31, 2018, at four different Italian transplant centers, with an overall follow-up of 5 years, were included in the study. Patients were stratified into pediatric (≤18 years) and adult (>18 years) groups. We compared graft survival, rejection rates, peritransplant complications (surgical, delayed graft function - DGF), and native disease recurrence. Statistical analysis included Kaplan-Meier, log-rank test, and Chi-square test.

We enrolled 445 KTR (104 pediatric, 341 adult). Compared to adults, pediatric patients had a shorter dialysis duration prior to transplant, a different distribution of dialysis modalities, exclusively received standard criteria donor kidneys, and had a higher prevalence of genetic kidney disease. Data show a significantly higher use of thymoglobulin induction in adults. As for maintenance therapy, all pediatric patients received steroids, and they were more frequently treated with azathioprine (12.5% vs 0.3%, p < 0.001) and cyclosporine (6.7% vs 0.6%, p < 0.001), whereas mTOR inhibitors were used exclusively in adults (25.2% vs 0%, p < 0.001). Mycophenolate mofetil was slightly more common in pediatric patients (86.5% vs 76.2%, p = 0.025). Graft loss at 5 years occurred in 14.0% of adults and 8.2% of pediatric patients, with no significant difference (p = 0.129) (Fig.1A).  The overall 5-year cumulative incidence of rejection was comparable between adults and pediatric patients (30.3% vs 37.8%, p = 0.166). However, pediatric patients had a significantly higher cumulative incidence of acute ABMR (25.4% vs 10.6%, p = 0.047) and acute TCMR (62.7% vs 39.4%, p = 0.012) (Fig.1B). Surgical and urological complications were comparable between groups, except for lymphocele, which was less frequent in pediatrics  (8.5% vs. 1.9% vs. 8.5%; P = 0.025) (Fig.1C). Within the first month after transplantation, infection rates were comparable (11.1% vs. 16.5%, p=ns). Pediatric recipients showed a significantly higher rate of recurrence at 1 year compared with adults (22.7% vs. 5.5%; P = 0.023), whereas no significant differences were detected at 2 and at 5 years after KT (Fig.1D).  

To the best of our knowledge, this is the first direct comparative study between pediatric and adult KT recipients, offering insights into the applicability of adult-based strategies in pediatric populations. Despite distinct immunological and clinical differences, graft survival, rejection rates, and disease recurrence were comparable between groups. Based on our results, future clinical trials should include pediatric cohorts to ensure equitable treatment across all age groups.