Routine Doppler Ultrasonography Does Not Differentiate Acute Tubular Necrosis and Rejection in Early Pediatric Kidney...

Area of Science:

• Nephrology
• Pediatric Transplantation
• Diagnostic Imaging

Background:

• Distinguishing acute tubular necrosis (ATN) from rejection in pediatric kidney transplant (KT) recipients is challenging, often requiring invasive biopsies.
• Doppler ultrasound-derived resistive index (RI) is a noninvasive tool for assessing graft status, but its diagnostic value in children is not well-established.

Purpose of the Study:

• To evaluate the utility of RI in differentiating ATN from rejection in pediatric KT recipients.
• To assess the diagnostic accuracy of established RI thresholds in this population.

Main Methods:

• Retrospective cohort study of 296 pediatric KT recipients from 2000-2021.
• Patients were categorized into uncomplicated, ATN, or rejection groups based on biopsy results.
• RI was measured at multiple time points post-transplant (24h, 3, 6, 12 months); linear mixed-effects models analyzed temporal trends.

Main Results:

• No significant difference in median RI was observed between ATN and rejection groups for either surveillance or clinically indicated biopsies.
• Established RI thresholds (0.7, 0.8) lacked specificity for differentiating complications.
• RI showed a temporal increase post-transplant and inverse correlation with recipient age but no association with ATN or rejection.

Conclusions:

• RI thresholds and temporal trends are insufficient to differentiate ATN from rejection in pediatric KT.
• The observed temporal RI increase likely represents systemic hemodynamic adaptation, not graft-specific pathology.
• Multimodal approaches integrating RI with clinical and biochemical markers are needed for improved noninvasive graft monitoring.