Background <p>Pelviureteric junction obstruction (PUJO) is the most common cause of pediatric hydronephrosis; however, distinguishing obstructive and non-obstructive dilatation remains challenging. Existing diagnostic modalities are limited by the lack of validation against objective measures of renal injury. Preoperative imaging is critical for guiding surgical decision-making; however, its correlation with histopathologic renal damage has not been fully elucidated.</p> Objectives <p>To evaluate the association between preoperative sonographic and nuclear scintigraphy parameters and intraoperative renal histopathology in children with congenital PUJO and to identify imaging predictors of significant renal parenchymal damage.</p> Methods <p>A prospective observational study was conducted on 60 children (&lt; 16&#xa0;years) with unilateral PUJO who underwent Anderson–Hynes pyeloplasty. Preoperative ultrasound parameters, including Society for Fetal Urology (SFU) grade, anterior–posterior pelvic diameter (APD), cortical thickness, and Doppler resistive index (RI), as well as nuclear scintigraphy parameters, including differential renal function (DRF), drainage half-time (T½), and renogram curve were recorded. Renal lower pole cortical biopsies were graded using Elder’s histopathology scoring system, with significant histologic damage defined as moderate-to-severe injury (score of ≥ 6). Statistical correlations and receiver operating characteristic analyses were performed to assess the predictive value of imaging parameters for histologic injury.</p> Results <p>High-grade hydronephrosis (SFU grade III–IV) was observed in 70.0% of patients, an anteroposterior diameter (APD) ≥ 20&#xa0;mm in 66.7%, and an elevated Doppler resistive index (RI ≥ 0.70) in 45.0%. Nuclear scan parameters demonstrated reduced differential renal function (DRF &lt; 40%) in 48.3% of patients and prolonged drainage half-time (T½ ≥ 20&#xa0;min) in 56.7% of patients. Histopathological examination revealed significant renal damage in 73.3% of kidneys. Significant associations, with histologic injury were observed for APD ≥ 20&#xa0;mm (<i>p</i> = 0.017), SFU grade ≥ III (<i>p</i> = 0.018), RI ≥ 0.70 (<i>p</i> = 0.030), DRF &lt; 40% (<i>p</i> = 0.008), and T½ ≥ 20&#xa0;min (<i>p</i> = 0.021). Receiver operating characteristic analysis demonstrated fair predictive accuracy across parameters, with area under the curve (AUC) values of 0.707 for SFU grade, 0.697 for RI, 0.640 for APD, 0.702 for DRF, and 0.673 for T½. SFU grade ≥ III showed the highest sensitivity (79.5%) but moderate specificity (56.2%), while DRF &lt; 40% demonstrated the highest specificity (81.2%) and positive predictive value (89.7%). Doppler RI ≥ 0.68 and T½ ≥ 20&#xa0;min exhibited balanced diagnostic performance, with sensitivities of 70.5% and 65.9% and specificities of 68.8% each. Negative predictive values were modest across all parameters (41.9–50.0%).</p> Conclusion <p>Ultrasonographic and nuclear imaging parameters correlate significantly with histopathologic injury in pediatric PUJO and serve as practical, noninvasive predictors of renal parenchymal damage. While ultrasonography provides higher sensitivity, nuclear scan indices offer greater specificity and predictive value, supporting a combined imaging approach for optimal evidence-based decision-making to preserve renal function in affected children.</p>