Abstract :
[en] The diagnosis procedure for kidney transplant recipients (KTR) with suspected acute rejection (AR) relies on needle biopsy. Noninvasive tests to predict nonrejection would be preferable. AR is associated with a recruitment of activated leukocytes into the transplant, which are characterized by a high metabolic activity and an increased uptake of glucose analog, Fluoro-deoxyglucose
( FDG). Thus, FDG-Positron emission tomography coupled with computed tomography (PET/CT) may help noninvasively distinguish nonrejection from AR. From January 2013 to February 2015, we prospectively performed 32 FDGPET/ CT in 31 adult KTR with suspected renal AR who underwent a biopsy. Biopsies were categorized as “normal”, “borderline”, “AR” or “others” according to Banff classification. PET/CT imaging was performed within 201 ± 18 minutes after i.v.
administration of 3.2 ± 0.2 MBq/kg of FDG, before any modification of immunosuppression. The mean standard uptake values (SUV) of both upper and lower renal poles were measured, with no threshold activity. Biopsies were diagnosed as “normal”, “borderline”, “AR” or “others” in 8, 10, 8 and 6 (including 3 polyoma-BK nephropathies) cases. Mean SUV respectively reached 1.5 ± 0.2, 1.6 ± 0.3, 2.9 ± 0.8, 2.2 ± 1.2 in each category. Mean SUV of biopsy-proven AR was significantly higher than “normal” cases (p<0.01). No difference was found between “normal” vs. “borderline”, or between “AR” vs. “others” histopathology. Still, a positive correlation between mean SUV and acute composite (g+i+t+v+ptc) Banff score was found, with a coefficient of 0.70 (p<0.001). Sensitivity and specificity of FDG-PET/CT in detecting pathological biospies were respectively
92.3% and 36.8%, with a mean SUV threshold at 1.4. FDG-PET/CT imaging may help discriminate nonrejection, thereby avoiding unnecessary transplant biopsy in KTR with suspected AR.
