Kidney transplantation – colour doppler and contrast-enhanced ultrasound in the early postoperative assessment of delayed graft function: retrospective results and pilot prospective findings

INTRODUCTION: Delayed graft function (DGF) remains a relevant early complication after kidney transplantation (KT), and reliable non-invasive imaging markers may improve postoperative graft assessment. MATERIALS AND METHODS: We retrospectively evaluated 381 KT recipients who underwent colour Doppler (CD) ultrasound (US) on postoperative day (POD) 1 and before discharge between January 2013 and February 2022. Resistive index (RI) measurements were analyzed in relation to DGF, defined as the need for at least one dialysis session within the first postoperative week. A prospective pilot subgroup of 25 recipients transplanted between February 2021 and February 2022 also underwent contrast-enhanced US (CEUS) between POD 1 and 3, with analysis of wash-in slope (WIS), time to peak (TTP), peak intensity (PI), and area under the curve (AUC). RESULTS: In the retrospective cohort, 71 (18.6%) developed DGF. Higher RI values on POD 1 and before discharge were significantly associated with DGF. In the CEUS pilot subgroup, 7 patients (28.0%) developed DGF. Among CEUS-derived parameters, AUC was significantly associated with DGF, with lower values in patients who developed DGF and a valuable ROC AUC of 0.794. CONCLUSIONS: These findings support a role for early postoperative CD in graft function assessment and suggest that CEUS-derived AUC may provide valuable complementary information in the early evaluation of grafts for DGF. However, the CEUS results are exploratory and require validation in larger prospective studies.