Objective and hypotheses: To assess the role of quantitative contrast-enhanced ultrasound (CEUS) and two-dimensional shear-wave elastography (2D-SWE) for the differentiation of kidney allografts with significant histopathological injury. Three hypotheses were explored. (1) Quantitative CEUS parameters of kidney allografts are associated with histopathological changes based on the Banff criteria. (2) 2D-SWE values of kidney allografts are associated with histopathological changes based on the Banff criteria. (3) When quantitative CEUS parameters and 2D-SWE values of kidney allografts are normal, we can conclude that no significant histopathological injury occurred in the kidney allograft.
Methods: 64 patients were enrolled in this prospective observational study. Biopsies were performed following CEUS, 2D-SWE, and blood examination.
Results: 28 biopsy specimens had minimal changes (MC group), while 36 had significant injury (SI group). Of these, 12 had rejection (RI group) and 24 non-rejection injury (NRI group). In RI and NRI groups, temporal difference in time to peak (TTP) between medulla and cortex (ΔTTPm-c) was significantly shorter compared to the MC group (5.77, 5.92, and 7.94 s, respectively). Additionally, RI group had significantly shorter medullary TTP compared to the MC group (27.75 vs. 32.26 s, respectively). In a subset of 41 patients with protocol biopsy at 1-year post-transplant, ΔTTPm-c was significantly shorter in the SI compared to the MC group (5.67 vs. 7.67 s, respectively). Area under receiver operating characteristic curves (AUROCs) for ΔTTPm-c was 0.69 in all patients and 0.71 in patients with protocol biopsy.
53 patients were included in the 2D-SWE analysis. Of these, 42 had biopsy proven clinically insignificant fibrotic changes (IF group) and 11 had clinically significant fibrotic changes (SF group). 2D-SWE values did not differ between the two groups. However, patients with higher body mass index (BMI 䁥 25 kg/m2) had significantly lower cortical 2D-SWE values (16,78 kPa vs 19,22 kPa, respectively).
Conclusions: RI and NRI groups had shorter ΔTTPm-c compared to the MC group. AUROCs for both patient groups were good, making ΔTTPm-c a promising CEUS parameter for distinguishing patients with significant histopathological injury. 2D-SWE could not differentiate between patients with clinically significant and clinically insignificant fibrotic changes. 2D-SWE values were significantly lower in patients with BMI 䁥 25 kg/m2.
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