Aim: To assess the utility of CPR in the follow-up of pyeloplasty and compared it with the commonly used APD of the pelvis and renal scintigraphy.
Methods: A prospective cohort study was done from July 2016 to October 2017. During this period 73 pyeloplasties were done, and 62 cases meeting the inclusion criteria were enrolled. All the children underwent ultrasound and Technetium-99 m Ethylene dicysteine isotope renogram (EC) scan before and after pyeloplasty. APD and CPR values were measured on USG and compared with isotope renogram outcomes in these children in the preoperative versus postoperative period. Two defined objective variables ΔAPD, percent ΔAPD, and ΔCPR, percent ΔCPR were compared with categorical variables that would predict the surgical outcome as - failed, successful or equivocal. Multinomial logistic regression and receiver operating curve (ROC) analysis were used to identify predictive accuracy.
Results: The mean (range) APD value recorded in the preoperative period was 3.67 cm (1.40–8.00 cm), which decreased to 1.67 cm (0.40–6.50) postoperatively, which was 54.2% lower (P=<0.001). The mean (range) CPR value decreased from 5.96 (1.20–20.00) in the preoperative period to 2.57 (0.43–10.90) postoperatively, which was 56.8% lower (P=<0.001). On multinomial logistic regression analysis, ΔCPR was found to be a significant predictor of outcome with an overall accuracy of 95.1%, change in CPR was a better predictor of success after pyeloplasty as compared to the change in APD, which had an overall accuracy of 85.2% (p = 0.01). Further, on ROC curve analysis, we observed that ΔCPR and %ΔCPR can strongly predict successful pyeloplasty with a sensitivity of each 96% and 98% respectively, and AUC of 0.897 and 0.799 respectively.
Conclusion: ΔCPR can identify successful pyeloplasty with a strong prediction than ΔAPD and thus renal scans can be avoided if there is a visible improvement in CPR on follow-up. Using this parameter, we can avoid unnecessary repeated nuclear scans based on persistent high APD values and optimize resource utilization. We recommend the use of CPR in routine practice in the preoperative and postoperative follow-up of PUJ obstruction following pyeloplasty.