Calyx to parenchyma ratio (CPR): a new tool in the armamentarium as predictor of success after pyeloplasty

Antero-posterior transpelvic diameter (AP-TPD) and renal scintigraphy varies significantly in a hydronephrotic kidney following pyeloplasty and is not a reliable parameter due to various factor. This juxtaposes the need for an alternative parameter. We hypothesise that the Calyx to Parenchymal Ration (CPR) which measures the depth of the calyx and parenchymal thickness in a hydronephrotic kidney may act as that alternative parameter. We aim to assess the CPR and compared it with the commonly used parameter AP-TPD of pelvis and renal scintigraphy before and after pyeloplasty. It was a prospective cohort study done in the department of Pediatric Surgery, JIPMER, Pondicherry, from July 2016 to October 2017. Sixty-one cases of pyeloplasties were included in the study group meeting all the inclusion criteria. All children underwent ultrasound and renal scintigraphy and then underwent pyeloplasty. AP-TPD and CPR values were compared with nuclear scan outcomes in these children in the pre-operative versus post-operative period. Mean AP-TPD in the pre-operative was 3.67 cm which decreased to 1.67cm post-operatively. The mean CPR value decreased from 5.96 in the pre-operative to 2.57 post-operatively which was 56.8% lower. Change in CPR was found to be a better predictor of success after pyeloplasty with an overall accuracy of 95.1% as compared to change in AP-TPD which had an overall accuracy of 85.2%. CPR is a better predictor of successful surgical outcome and can be used routinely in postoperative follow-up after pyeloplasty.