The accuracy of ultrasound viscoelastic imaging in evaluating renal fibrosis and interstitial inflammation of chronic kidney disease.

BACKGROUND

Accurate evaluation of renal fibrosis and interstitial inflammation grades is necessary to improve the prognosis of patients with chronic kidney disease (CKD). However, non-invasive and accurate diagnostic methods are lacking. In this regard, shear wave elastography, which measures tissue viscosity and elasticity, may be a promising alternative. Therefore, this study aimed to evaluate the diagnostic performance of individual viscoelastic parameters, combined viscoelastic parameter models, and combined clinical parameter models in assessing the grades of renal fibrosis and interstitial inflammation.

METHODS

This prospective study recruited 22 and 47 patients with CKD in the reproducibility and validity trials, respectively, between October 2023 and June 2024. The mean elasticity (Emean), maximum elasticity (Emax), minimum elasticity (Emin), and mean viscosity (Vmean) were obtained using two-dimensional shear-wave elastography (2D-SWE). The biopsy specimens were assessed to determine the grades of renal fibrosis and interstitial inflammation. Additionally, clinical data, including protein-to-creatinine ratio, and estimated glomerular filtration rate (eGFR), were obtained from the patients’ medical records. Multiple logistic regression models were constructed, including viscoelastic models and clinical models, and their diagnostic performance was evaluated using receiver operating characteristic curves.

RESULTS

The Emean, Emax, Emin and Vmean demonstrated good to excellent intra-observer consistency (ICCs = 0.839–0.929, p < 0.001). The area under the curve (AUC) of Emax combined with Vmean was not significantly superior to that of Emax alone in distinguishing fibrosis grades (0.740 [95% confidence interval (CI): 0.591–0.857] vs. 0.737 [95% CI: 0.589–0.855], p > 0.05). In contrast, Emax combined with eGFR demonstrated an AUC of 0.902 (95% CI: 0.780–0.969), a sensitivity of 93.3%, and a specificity of 84.4% in distinguishing fibrosis grades. Individual Vmean achieved an AUC of 0.919 (95% CI: 0.801–0.978), a sensitivity of 100%, and a specificity of 86.1% in differentiating between the grades of renal interstitial inflammation.

CONCLUSIONS

A combination of Emax and eGFR was useful for detecting severe renal fibrosis. Additionally, Vmean was identified as a potentially useful parameter for differentiating interstitial inflammation grades, although this finding requires validation in larger cohorts given the limited samples with severe interstitial inflammation. TRIAL REGISTRATION (RETROSPECTIVELY REGISTERED): NCT06961162. Registration date: 2025-04-29.