Comparative Morphological and Hemodynamic Profiles of Renal Allografts and Native Kidneys: A Retrospective Cohort Study Assessing Ultrasound Surveillance Parameters

Abstract

Introduction: Renal transplantation remains the optimal treatment for end-stage renal disease (ESRD), yet long-term allograft survival continues to be suboptimal. Although ultrasound surveillance is fundamental in post-transplant monitoring, uncertainties persist regarding the morphological and hemodynamic comparability of transplanted versus native kidneys, as well as the diagnostic reliability of conventional parameters for detecting vascular complications. Methods: This retrospective cohort study evaluated 34 adult patients (24 renal transplant recipients and 10 native-kidney controls) who underwent renal ultrasonography at Zhongnan Hospital of Wuhan University between January 2025 and May 2025. Ultrasound assessments included morphological measurements (length, width, height, parenchymal and cortical thickness), hemodynamic indices such as the resistive index (RI) and peak systolic velocity (PSV), and contrast-enhanced ultrasound (CEUS) perfusion metrics (arrival time, time-to-peak, and area under the curve [AUC]). Group comparisons were performed using the Mann-Whitney U test. Associations between age and hemodynamic parameters were examined using linear regression. Diagnostic performance for angiography-confirmed vascular complications was evaluated using receiver operating characteristic (ROC) curve analysis. Results: Transplanted kidneys demonstrated morphology comparable to native kidneys across all dimensions (length: 10.82 ± 1.91 vs 10.10 ± 1.06 cm, p = 0.22; cortex thickness: 0.81 ± 0.10 vs 0.86 ± 0.09 cm, p = 0.10). Hemodynamic parameters were similarly preserved, with no significant group differences in RI (0.75 vs 0.73, p = 0.38) or PSV (102.5 vs 101.7 cm/s, p = 0.88). Among transplant recipients, age showed no association with RI ( β = 0.000, p = 0.969) or PSV ( β = −0.1, p = 0.939). ROC analysis demonstrated limited diagnostic utility for detecting vascular complications (AUC:PSV = 0.49; CEUS arrival time = 0.64; CEUS time-to-peak = 0.62; CEUS:AUC = 0.59). Conclusion: Renal allografts exhibit structural and hemodynamic profiles comparable to native kidneys, with stable hemodynamic performance across age groups. However, the poor diagnostic accuracy of conventional Doppler and CEUS parameters for vascular-complication detection indicates the need for more advanced and sensitive monitoring approaches in transplant surveillance.