Renal allograft acute rejection must be promptly diagnosed since its reversibility is related to the readiness in which treatment is initiated. The aim of this study was: 1) to establish a quantitative method to evaluate kidney rejection and acute tubular necrosis (ATN); 2) to assess the potential role of 99mTc-mononuclear leukocytes scintigraphy in the diagnosis of renal rejection and differential diagnosis of ATN. One hundred and sixty studies were performed in 80 renal transplant patients at the first and fifth day after transplantation. Autologous cells were used for labeling. Images were obtained at 30 minutes, 3 hours and 24 hours after intravenous administration of 444 MBq (12 mCi) of labeled cells. There was abnormal labeled cells uptake in 27 of 31 cases of rejection and in 6 of 8 cases of ATN. The results of each patient were compared with clinical findings. Doppler scanning detected 18 of 31 cases of rejection. Rejection diagnosis sensitivity and specificity rates using scintigraphy were 87.1% and 100%, respectively, and 58.1% and 100%, respectively using ultrasound. Renal biopsy was performed in eight patients which demonstrated seven cases of rejection and one case of ATN. These results suggest that 99mTc-mononuclear leukocytes imaging may be useful in the early diagnosis of rejection and in the differential diagnosis of ATN.

Keywords: 99mTc-mononuclear leukocytes, Renal allograft, Rejection, Diagnosis