Objective ·To explore the predictive value of diuretic renal scintigraphy parameters such as 20-minute residual rate (R₂₀) for pyeloplasty in children with congenital unilateral ureteropelvic junction obstruction (UPJO). Methods ·The clinical data and diuretic renal scintigraphy results of 110 children with congenital unilateral UPJO who were first treated at the Department of Nuclear Medicine, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine from August 2018 to August 2023 were retrospectively analyzed. The imaging results and the progress of hydronephrosis were followed up after the first diuretic renal scintigraphy. According to the outcome event of pyeloplasty due to the progression of hydronephrosis, the children were divided into operation group and non-operation group. Age, gender, side of hydronephrosis, and baseline diuretic renal scintigraphy parameters including blood perfusion rate (BPR), differential renal function (DRF), time to peak (T_max), time to half (T_1/2) and R₂₀ were compared between the two groups. Logistic regression was used to analyze the effect of various parameters on the progression of hydronephrosis. The receiver operating characteristic (ROC) curve was used to analyze the predictive value of diuretic renal scintigraphy parameters for surgical intervention. Wilcoxon test was used to compare the examination parameters of two diuretic renal dynamic imaging. Results ·During the follow-up, 60 children underwent pyeloplasty after progression, and the other 50 children did not progress. The differences in DRF, T_max, T_1/2 and R₂₀ between the two groups of children at baseline were statistically significant (all P<0.05). Univariate and multivariate Logistic regression analysis showed that only R₂₀ was an independent predictor of pyeloplasty (OR=4.730, 95%CI 1.009-1.178, P=0.030). R₂₀ predicted pyeloplasty with a sensitivity of 88.3%, specificity of 56%, the area under the ROC curve of 0.758 (95% CI 0.667-0.850, P=0.000), and the cut-off value of 90.08%. During the follow-up, 38 children underwent the second diuretic renal scintigraphy, and the DRF was lower than before. The difference between the two DRFs was statistically significant (Z=-2.589, P=0.010), especially in children with R₂₀≥90.08% (Z=-2.166, P=0.030). R₂₀ in the non-operation group decreased significantly compared with the baseline (Z=-2.062, P=0.039). However, R₂₀ in the operation group was higher than baseline, but the difference was not statistically significant (P>0.05). Conclusion ·R₂₀ plays an important role in the prediction of pyeloplasty in children with congenital unilateral UPJO. For children with R₂₀≥90.08%, pyeloplasty should be performed as soon as possible to prevent further deterioration of renal function.