Comparison of Reliability of Kidney Ultrasound Findings After Pyeloplasty Versus Kidney Isotope Scans for Success in Patients with Ureteropelvic Junction Obstruction

Background: New parameters called the pelvis-cortex (P/C) ratio, and percentage of pelvic improvement (PI) in the anteroposterior diameter (APD) are used for patients with ureteropelvic junction obstruction who have undergone pyeloplasty. Early improvement in these ultrasonic parameters can prevent isotope scanning for a successful repair. Methods: The data of pediatric patients (age range: 0 - 14 years) who underwent open pyeloplasty in Mofid Children Hospital pediatric surgery ward from 2017 to 2021 with follow-up longer than 12 months were analyzed retrospectively. This study encompassed only those children whose ultrasound and Technetium-99m diethylene triamine pentaacetic acid (DTPA) renal information were available before and after surgery. Results: A total of 67 patients meeting inclusion criteria were registered. The mean age at operation was 30 ± 37.44 months. The mean pelvic APD before surgery was 33.93 mm. The mean kidney cortex diameter before surgery was 5.26 ± 2.07 mm. The mean P/C ratio before surgery was 7.56 ± 4.38. The mean preoperative split renal function was documented at 42.23%. The mean follow-up duration was 32 months. The mean APD 3 months after surgery was 18.1 mm. The mean kidney cortex diameter 3 months after surgery was 6.72 mm. The mean P/C ratio 3 months after surgery was 3.09. The PI in APD 3 months after surgery was 43.29%. The mean APD 6 months after surgery was 15.43 mm. The mean kidney cortex diameter 6 months after surgery was 7.24 mm. The mean P/C ratio 6 months after surgery was 2.8. The mean PI in APD 6 months after surgery was 50.83%. The mean postoperative tracer clearance half-time in diuretic renography was 20.77 minutes. In receiver operating characteristic curve analysis, it was observed that PI in APD > 12% in 3 months after surgery versus DTPA 6 months after surgery could predict successful pyeloplasty with sensitivity, specificity, and area under the curve (AUC) equal to 98.44%, 66.67%, and 0.87, respectively. The PI in APD > 26% 6 months after surgery versus DTPA 6 months after surgery could strongly predict successful pyeloplasty with sensitivity and specificity of 100% and AUC of 1. Conclusions: This study identified that PI in APD > 26% at 6 months after surgery can strongly predict successful pyeloplasty and is a strong predictor of surgical outcome. Unnecessary repeated nuclear scans 6 months after surgery can be avoided using the aforementioned parameter.