Most renal transplant surveillance biopsies [SBx] are taken within the first 12 months of transplantation and there is growing evidence that the detection of subclinical rejection in SBx is a powerful tool in predicting subsequent clinical outcomes. The clinical use of late surveillance biopsies, defined as biopsies taken in the absence of allograft dysfunction after the first year post transplant is not well described particularly in patients receiving minimal immunosuppression.

The aim of the study was to establish subclinical pathology on SBx carried out at 3 years post-transplant and to determine if they could be used to predict clinical outcomes.

We carried out 3 year SBx on 100 patients [64m, 36f, mean age 46.37 ± 12.4 yrs, 56 live donors, mean HLA mm 3.43 ± 1.53] transplanted at our centre between 2005 and 2009. The mean time to SBx was 3.21 ± 0 .37 years post-transplant; mean follow up post biopsy was 1.89 ± 1.20 years. All patients received monoclonal antibody induction, a week of steroids post-transplant and a tacrolimus based immunosuppressive regime. Mean plasma creatinine at SBx was 125.53 ± 35.54 Μmol/l. All patients had stable allograft function and no proteinuria. The biopsy findings were not used to change immunosuppressive therapy.

The major histological findings are shown in table 1. Of the patients with rejection, 9/16 [56.3%] had cellular rejection [TCMR], 3/16 [18.8%] antibody mediated rejection [AMR] and 4/16 [25.0%] had transplant glomerulopathy [TG]. 9/16 [42.9%] patients had donor specific antibodies at the time of biopsy. Patients with DSA had significant evidence of microcirculatory inflammation; 5/9 [55.6%] had glomerulitis, 4/9 [44.4%] had peritubular capillaritis and 4/9 [44.4%] had double contours.

This study shows that subclinical alloimmune injury is seen in a significant number of SBx at 3 years post transplant without renal dysfunction or proteinuria. These SBx may predict graft dysfunction and failure, signalling the need for augmented immunosuppression before it is too late.

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