Diagnostic value of contrast-enhanced ultrasound in the activity of idiopathic retroperitoneal fibrosis: a retrospective study

Objectives To explore the diagnostic value of contrast-enhanced ultrasound (CEUS) in the disease activity of idiopathic retroperitoneal fibrosis (IRPF). Methods This retrospective study included 148 CEUS examinations from 63 patients with IRPF treated in our hospital from April 2016 to September 2021. They were divided into two groups: IRPF active group (69 examinations) and inactive group (79 examinations). Uni- and multivariable analyses were used to identify independent risk factors for IRPF activity. Receiver operating characteristic (ROC) curves were drawn to establish different diagnostic models to evaluate the diagnostic value of IRPF activity. The z test was used to compare the differences of the area under the curves (AUCs). The value of CEUS in evaluating the variation of disease activity over time was also investigated between repeat patient studies. Results Univariate and multivariate logistic regression analyses revealed the thickness [odds ratio (OR) = 14.125, 95% confidence interval (CI) = 3.017–66.123] was the most significant independent risk factor for IRPF activity ( P < 0.01). The best diagnostic model was model 3, which was established by CEUS score combined with thickness. The AUC was 0.944 (95%CI = 0.912–0.977), and the sensitivity and specificity were 89.86% and 86.08%, respectively. The diagnostic performance was not significantly improved after combining clinical symptom (back pain) and laboratory indicators [erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)]. Compared with before treatment, the CEUS score and thickness were significantly decreased after treatment ( x 2 = 14.580, P < 0.001 and z = 4.708, P < 0.001, respectively). Conclusion CEUS has good diagnostic value for IRPF disease activity. Key points • Thickness and contrast-enhanced ultrasound score were significantly higher in the active group than those in inactive group (P < 0.001). • With thickness of 4 mm and contrast-enhanced ultrasound 2 score as optimal cut-off values, the sensitivity and specificity were 89.86%, 81.01% and 52.17%, 100.00%, respectively. • During follow-up, when the disease progressed, the change of CEUS score was earlier than the change of thickness.