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Improved resistance index in renal allograft with reversed diastolic flow

Objective To study the accuracy of improved resistance index (RI) in judging the prognosis in renal allograft with reversed diastolic flow. Methods According to the transplant nephrectomy, patients with reversed diastolic flow in renal allograft were classified into two groups:surgical group (n = 5) and nonsurgical group (n = 19). The differences in improved RI between two groups were compared by using Student's t test. Improved RI was defined as a ratio of peak systolic velocity plus peak diastolic velocity divided by peak systolic velocity. Receiver operating characteristic (ROC) curve was constructed for improved RI to evaluate diagnostic accuracy in judging the prognosis in renal allograft with reversed diastolic flow. Results Improved RI in surgical group ( 1.57 ± 0. 26)was higher than in nonsurgical group (1.22 ± 0. 08) (P＜＜0. 05). Areas under ROC curve for improved RI was 0. 979. An improved RI threshold of 1.31 had 100 % sensitivity, 90 % specificity, 71%positive predictive value, and 100 % negative predictive value for renal allograft with reversed diastolic flow loss as the maximum Youden index was 90 %. Applying this cutoff value to predict the function of renal allograft with reversed diastolic flow recovery, the accuracy was 92 % (maximum) or 83 %(minimum). Conclusion Improved RI can not only serve as a useful noninvasive index to predict renal allograft with reversed diastolic flow loss, but also to predict the function of renal allograft with reversed diastolic flow recovery. 
 
Key words: 
Ultrasonography;  Reversed diastolic flow;  Renal allograft;  Resistance index; Receiver operating characteristic curve