[Evaluation of renal allograft dysfunction employing dynamic SPECT with 99mTc-MAG3 and graph plot analysis].

To estimate renal blood flow and tubular function in transplanted kidneys, we applied the 4 compartments model and the graphic analysis method to 99mTc-MAG3 dynamic SPECT and calculated some parameters, i.e. K1 (renal influx rate constant), K3 (tubular transporting rate constant), Vd12 (intrarenal distribution volume), and others. Twenty-three renal transplant recipients were examined and divided into following 3 groups according to their serum creatinine levels (SCr); Group I: less than 1.3 mg/dl (1.1 +/- 0.3, n = 7), Group II: 1.4-2.5 mg/dl (1.8 +/- 0.3, n = 11), and Group III more than 2.6 mg/dl (3.9 +/- 0.9, n = 5). The K3 value became lower in the order of Group I > II > III, and well correlated with blood urea nitrogen (BUN, r = -0.95, p < 0.001) and creatinine clearance (Ccr, r = 0.78, p < 0.001). The K1 value reduced markedly in Group III despite of no difference between Group I and II. Although the K1 value also correlated with SCr, BUN and Ccr, correlation coefficients were smaller than those with the K3. Effective renal plasma flow derived from K1 and K3 showed a good correlation with the tubular extraction rate by Bubeck's method. From these results and clinical conditions including histopathological findings it is suggested that K1, K3 and Vd12 are useful parameters of renal central arterial blood flow, renal peripheral arteriolar blood flow and renal 99mTc-MAG3 uptake function, respectively.