Contrast-enhanced ultrasound (CEUS) as a follow-up method after the focal treatment of renal tumors: systematic review and meta-analysis

Context Contrast-enhanced ultrasound (CEUS) is a cost-effective radiation-free diagnostic method that can be used for renal tumor postoperative visualization after ablative treatment. Objective To assess CEUS diagnostic accuracy comparing with CT and MRI as a follow-up method in short-term and long-term postoperative periods after renal tumor ablation. Materials and methods A systematic review and meta-analysis were performed in Scopus and Medline databases using the query "(kidney OR rena* OR RCC) AND (ablation OR RFA OR MWA OR cryo*) AND CEUS". The endpoint of the study was the evaluation of the overall accuracy of CEUS. Results Twelve trials were included in the review. With CT or MRI as a reference, for a short-term group (< 6 weeks after ablation) pooled sensitivity was 90.2%, I-2 = 0%; pooled specificity was 99.3%, I-2 = 0%; pooled NPV was 98.6%, I-2 = 0%; pooled PPV was 94.6%, I-2 = 0%; the AUC on the SROC curve was 0.971. For the long-term group (> 6 weeks after ablation), pooled sensitivity was 95.3%, I-2 = 0%; pooled specificity was 97.6%, I-2 = 0%; PPV was 74.2%, I-2 = 4%; NPV was 99.4%, I-2 = 5%; AUC = 0.93. Conclusion CEUS has high sensitivity and specificity in ruling out the presence of local recurrence after renal tumor ablation with a higher risk of false-positive results within follow-up > 6 weeks compared with that for CT or MRI. Further studies with a unified protocol and morphological control of local renal tumor recurrence after ablation are needed.