Protocol biopsies in pediatric renal transplant recipients on cyclosporine versus tacrolimus-based immunosuppression

Subclinical Rejection and Immunosuppression in Pediatric Kidney Transplant Recipients : Single Centre Study

Background: By the time of histological confirmation of rejection is achieved, renal scarring may for treatment as a realistic option . This study aims to study the subclinical pathological graft data and to evaluate the histopathological impact of different immunosuppression protocols in pediatric renal transplant recipients. Methods: This is a case series that included twenty living donor renal transplant recipients. All included cases received the classic triple immunotherapy for at least one month post-transplantation [Steroids, calconurine inhibitors (CNI), and mycofenlolic mofetile (MMF)]. Based on their immunological risk stratification; included cases were divided into 2 groups: group (A) continued on CNI based triple therapy protocol; group (B) shifted to evirolimus /low dose CNI protocol. Surveillance biopsies were done for all cases at one and four month post-transplantation. Results: One and four month biopsies revealed subclinical rejection (including borderline changes) in 4 (20%) cases and 6 (30%) cases respectively. The number of patients received tacrolimus/MMF therapy significantly increased (p=0.02) while that of patients on everloimus/low dose CNI significantly decreased (p=0.014) due to drug modifications based on four month surveillance biopsy data. Conclusion: Subclinical rejection is not uncommon in pediatric renal graft recipients which makes surveillance biopsy might be of help. Early usage of evirolimus/low CNI protocol is associated with higher rejection rate than triple therapy.

Non-invasive differentiation of non-rejection kidney injury from acute rejection in pediatric renal transplant recipients

Acute kidney injury (AKI) is a major concern in pediatric kidney transplant recipients, where non-alloimmune causes must be distinguished from rejection. We sought to identify a urinary metabolite signature associated with non-rejection kidney injury (NRKI) in pediatric kidney transplant recipients. Urine samples (n = 396) from 60 pediatric transplant participants were obtained at time of kidney biopsy and quantitatively assayed for 133 metabolites by mass spectrometry. Metabolite profiles were analyzed via projection on latent structures discriminant analysis. Mixed-effects regression identified laboratory and clinical predictors of NRKI and distinguished NRKI from T cell-mediated rejection (CMR), antibody-mediated rejection (AMR), and mixed CMR/AMR. Urine samples (n = 199) without rejection were split into NRKI (n = 26; ΔSCr ≥25%), pre-NRKI (n = 35; ΔSCr ≥10% and <25%), and no NRKI (n = 138; ΔSCr <10%) groups. The NRKI discriminant score (dscore) distinguished between NRKI and no NRKI (AUC = 0.86; 95% CI = 0.79-0.94), confirmed by leave-one-out cross-validation (AUC = 0.79; 95% CI = 0.68-0.89). The NRKI dscore also distinguished between NRKI and pre-NRKI (AUC = 0.82; 95% CI = 0.71-0.93). In a linear mixed-effects regression model to account for repeated measures, the NRKI dscore was independent of concurrent rejection, but there was a non-statistical trend for higher dscores with rejection severity. A second exploratory classifier developed to distinguish NRKI from clinical rejection had similar test characteristics (AUC = 0.81, 95% CI = 0.70-0.92, confirmed by LOOCV). This study demonstrates the potential of a urine metabolite classifier to detect NRKI in pediatric kidney transplant patients and non-invasively discriminate NRKI from rejection.

Can pre-implantation biopsies predict renal allograft function in pediatric renal transplant recipients?

Objectives:

To determine the utility of pre-implantation renal biopsy (PIB) to predict renal allograft outcomes.

Methods:

This is a retrospective review of all patients that underwent PIB from January 2003 to December 2011 at the Great Ormond Street Hospital for Children in London, United Kingdom. Thirty-two male patients (56%) aged 1.5-16 years (median: 10.2) at the time of transplantation were included in the study and followed-up for 33 (6-78) months. The results were compared with 33 controls.

Results:

The PIB showed normal histopathological findings in 13 patients (41%), mild chronic vascular changes in 8 (25%), focal tubular atrophy in one, moderate to severe chronic vascular change in 3, mild to moderate acute tubular damage in 6, and tissue was inadequate in one subject. Delayed graft function (DGF) was observed in 3 patients; 2 with vascular changes in PIB, and one with normal histopathological findings. Two subjects with PIB changes lost their grafts. The estimated glomerular filtration rate at 3-, and 6-months post-transplantation was lower in children with abnormal PIB changes compared with those with normal PIB. There was one case of DGF in the control group, and 4 children lost their grafts including the one with DGF.

Conclusion:

Pre-implantation renal biopsy can provide important baseline information of the graft with implications on subsequent medical treatment for pediatric renal transplant recipients.