Radiofrequency ablation of renal tumours: diagnostic accuracy of contrast-enhanced ultrasound for early detection of residual tumour

Objective To evaluate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in the early detection of residual tumour after radiofrequency ablation (RFA) of renal tumours. Methods Patients referred to our institution for RFA of renal tumours prospectively underwent CEUS and computed tomography (CT) or magnetic resonance imaging (MRI) before, within 1 day and 6 weeks after treatment. Identification of residual tumour was assessed by three blinded radiologists. Reference standard was CT/MRI performed at least 1 year after RFA. Results A total of 66 renal tumours in 43 patients (median age 62 years; range 44–71.5) were studied. Inter-reader agreement ( κ value) was 0.84 for CEUS. Prevalence of residual disease was 19%. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV), respectively, were as follows: 64% [confidence interval (CI) 39–84], 98% [CI 91–100], 82% [CI 52–95] and 92% [CI 83–97] on 24-h CEUS; 79% [CI 52–92], 100% [CI 94–100], 100% [CI 74–100] and 95% [CI 87–100] on 6-week CEUS; 79% [CI 52–92], 95% [CI 86–98], 79% [CI 52–92] and 95% [CI 86–98] on 24-h CT/MRI; and 100% [CI 72–100], 98% [CI 90–100], 91% [CI 62–98] and 100% [CI 93–100] on 6-week CT/MRI. Conclusion CEUS has high specificity for the early diagnosis of residual tumour after renal RFA.