Abstract
Introduction: Interstitial fibrosis (IF) is frequently present in renal biopsy specimens obtained from transplant recipients who receive tacrolimus (TAC) and prednisone as maintenance immunosuppression, especially in those in whom the associated trough TAC levels are elevated. In contrast, little information exists on the kidney histology of patients on a steroid free (SF) immunosuppression regimen. The role that the exposure to TAC [trough levels or area under the curve (AUC)] has on biopsy findings remains poorly defined.
Aims: To report the 6 month renal transplant surveillance biopsy results of patients receiving SF immunosuppression. The relationship between TAC usage and the biopsy findings was also investigated.
Methods: Medical records from 14 pediatric renal transplant recipients who received a maintenance immunosuppression regimen consisting of TAC & mycophenolate mofetil were reviewed for age at time of transplant, gender, ethnicity, donor type, cold ischemia time, TAC dose and trough level and estimated GFR at time of biopsy. TAC AUC was assessed in 7 patients. Data is presented as mean (±SD). Results: Of the 14 patients (mean age: 11.8±5.23 yrs), 10/14 (71%) were caucasian, 9/14 (64%) were male, and 10/14 (71%) received a living related donor transplant, with a cold ischemia time of 7.66±8 hrs. Surveillance biopsies were performed at a mean time of 200.92±33.3 days post transplantation. Serum creatinine at the time of biopsy was 0.94±0.46 mg/dl with a Schwartz estimated GFR of 86.88±34.29 ml/min/1.73 m2. TAC dose at time of biopsy was 0.17±0.25 mg/kg/day and the associated trough level was 6.36±1.52 ng/ml. In the 7 patients who had done TAC pharmacokinetics, the mean C0 was 6.75±1.28 ng/ml and AUC 110.8±32.37 [h × (ng/ml)]. Based on the Banff ‘97 working classification of renal allograft pathology, interstitial fibrosis (IF) involved a mean 17.3±7.66% of the biopsy specimen and was present in 10/14 (71%) biopsies. There was no correlation found between trough TAC level and % IF. A mean of 18.75±3.77 % IF was found in those who had TAC pharmacokinetics performed.
Conclusion: IF is frequently found in “well-functioning” renal transplants as early as 6 months post transplant in association with a SF, TAC based immunosuppression regimen in children. The potential correlation between transplant histology, trough TAC levels and TAC pharmacokinetics requires further study in a larger number of patients.
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Auron, A., Taboada, E., Reed, L. et al. 41 Renal Transplant Surveillance Biopsy Results in Children Receiving Steroid Free Immunosuppression. Pediatr Res 60, 497 (2006). https://doi.org/10.1203/00006450-200610000-00063
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DOI: https://doi.org/10.1203/00006450-200610000-00063