Value of quantitative contrast-enhanced ultrasound based on S-G filter theory in the diagnosis of chronic rejection of transplant kidney

Objective To explore the characteristics and differences of micro-perfusion between patients after transplant kidney with stable renal function, acute rejection and chronic rejection by contrast-enhanced ultrasound (CEUS) quantifying. Methods Thirty-three patients with stable renal function, 27 patients with acute rejection and 14 patients with chronic rejection were enrolled. The perfusion parameters of region of interest in renal cortex and medulla were obtained by CEUS offline data quantitative analysis software. The perfusion parameters in stable renal function group were compared with those in acute rejection and chronic rejection groups; furthermore, the value of color Doppler and CEUS in the diagnosis of chronic rejection was explored and compared. Results As for resistance index RI on color Doppler, it made no statistical difference among three groups (P>0.05). The perfusion parameters derived from CEUS quantitative analysis and Color Doppler parameter resistance index (RI) were not statistically different among renal function stabilization, acute rejection and chronic rejection groups (P>0.05); as compared with stable renal function group, there were marked reductions in peak intensity of cortex (PIc), peak intensity of medulla (PIm), ascending slope of cortex (a3c), ascending slope of medulla (a3m) and area under the curve of cortex (AUCc) in chronic rejection group. And mean transit time of cortex (MTTc) and mean transit time of medulla (MTTm) became significantly prolonged (P<0.05). Except for a3m, PIc and PIm were not significantly different between stable renal function and acute rejection groups (P<0.05). As compared with acute rejection group, MTTc and MTTm were significantly prolonged in chronic rejection group while AUCm and PIm declined markedly (P<0.05). When PIm<26.7dB, the diagnostic efficiency of chronic rejection was the highest and the sensitivity and specificity were 85.7% and 72.7% respectively. Conclusions As compared with color Doppler, CEUS quantitative parameters based on S-G filter theory can evaluate the micro-perfusion of transplant kidney more precisely and may provide diagnostic clue for chronic rejection. Key words: Kidney transplantation; Ultrasound contrast; Rejection