To evaluate the diagnostic performance of Doppler ultrasonography (DUS) for pediatric transplant renal artery stenosis (TRAS) using computed tomographic angiography (CTA) as the reference standard.

This retrospective single-center study included 61 pediatric renal transplant recipients [36 males; mean age, (10.0±3.6) years (SD)] who underwent 74 CTA examinations for suspected TRAS between January 2019 and February 2025. A total of 74 matched pairs of DUS and CTA examinations (49 TRAS, 25 non-TRAS) were analyzed. DUS parameters recorded included peak systolic velocity in the transplant renal artery (TRA-PSV), the renal-to-iliac PSV ratio (RIR), and resistive indices (RI) in segmental and interlobular arteries. Diagnostic performance was assessed against CTA, with ＞50% stenosis defined as the reference standard for TRAS. Receiver operating characteristic (ROC) curve analysis was used to determine optimal thresholds and the area under the ROC curve (AUC).

Among the DUS parameters, TRA-PSV (cut-off≥387 cm/s) demonstrated the lowest diagnostic performance (AUC=0.688; P＜0.01 for comparisons). For direct indicators, RIR (cut-off≥3.5) exhibited a significantly higher specificity than PSV, the difference is statistically significant (72% vs 48%, P＜0.001). For indirect indicators, interlobular artery RI (cut-off≤0.48) showed a significantly higher specificity than segmental artery RI (cut-off≤0.59), at 88% vs 72%, respectively, the difference is statistically significant (P＜0.001). The combination of direct (RIR≥3.5) and indirect (interlobular RI≤0.48) DUS features yielded a sensitivity of 62.3%, specificity of 93.2%, and positive predictive value (PPV) of 91.2% for diagnosing TRAS.

The combined DUS criteria of RIR≥3.5 and interlobular RI≤0.48 offer high specificity for diagnosing pediatric TRAS. Leveraging the diagnostic efficacy of DUS, particularly with these combined criteria, can significantly reduce unnecessary CTA examinations in pediatric patients.