Evaluation of Transplant Renal Artery Stenosis in Pediatric Recipients Using Duplex and High-Frequency Contrast-Enhanced Ultrasound Compared with Computed Tomography Angiography.

OBJECTIVE

To evaluate the diagnostic performance of duplex ultrasound (DUS) and high-frequency contrast-enhanced ultrasound (CEUS) for transplant renal artery stenosis (TRAS) in pediatric recipients.

METHODS

This study included 89 children who underwent 112 computed tomography angiography (CTA) examinations. Seventy matched triplets of DUS/CEUS/CTA constituted the derivation cohort, while 42 paired DUS/CTA formed a separate validation cohort for validating DUS criteria. DUS parameters (peak systolic velocity in transplant renal artery [TRA-PSV], renal-to-iliac PSV ratio [RIR], segmental and interlobular resistive indices [RI]) and high-frequency CEUS stenosis were recorded. Diagnostic performance, with CTA as the reference standard, was measured by the area under the receiver operating characteristic curve (AUC).

RESULTS

In the derivation cohort, the combined DUS thresholds (RIR ≥ 3.5 and interlobular RI ≤ 0.49) yielded a sensitivity of 52.4% and a specificity of 95.1% for diagnosing TRAS. The separate validation cohort showed high specificity (100%) of the combined DUS criteria. Among the 64 interpretable CEUS images, the AUC for TRAS diagnosis was 0.85 (sensitivity = 80%, specificity = 89.5%). In the subgroup with excellent image quality (n = 40), the AUC improved to 0.91 (sensitivity = 88.9%, specificity = 92.3%). For DUS-indeterminate (RIR < 3.5 and/or interlobular RI > 0.49) cases (n = 34), CEUS with excellent image quality (n = 20) achieved 87.5% sensitivity and 91.7% specificity. Application of the proposed DUS/CEUS diagnostic scheme could avoid 61.4% (43/70) of CTAs in the derivation cohort.

CONCLUSIONS

The combined DUS criteria (RIR ≥ 3.5 and interlobular RI ≤ 0.49) and CEUS demonstrated high specificity for diagnosing TRAS, thereby avoiding some unnecessary CTAs in pediatric recipients.