Assessment of treatment efficacy in radiofrequency ablation for renal tumors by contrast-enhanced ultrasonography

Abstract

Objective To discuss the utility of contrast-enhanced ultrasonography （CEUS） in the assessment of treatment efficacy of radiofrequency ablation （RFA） in patients with renal tumors. Methods Forty seven patients （40 renal cell carcinomas and 7 angiomyolipomas of kidney） with 49 renal tumors were treated with RFA. Tumors were ablated by laparoscopy-assisted （n 30） and open surgical （n=17） RFA. The CEUS and contrast-enhanced CT were performed 1 week after treatment to assess the necrotic area. Technical success was defined as elimination of areas that enhanced at imaging within the entire tumor. Results Forty seven （95.9%） of 49 tumors were successfully ablated. The mean length of the major axis at the maximal necrotic area was 4.6 cm. Compared with the lesions before RFA, the necrotic areas were bigger in 45 patients, identical in 3 patients, and smaller in 1 patient. Six lesions showed a residual enhancement at the portion adjacent to the normal renal pa renchyma on follow up CEUS, while 2 were confirmed by CT scans. The sensitivity and specificity of CEUS for detection of residual tumors were 100.0% and 91.8%, respectively. All patients survived in the follow up period ranging from 4 to 21 months. Conclusion CEUS combined with CT could be useful for evaluating treatment efficacy of RFA for renal tumors. Key words: Ultrasonography; Imge enhancement; Kidney neoplasms; Radiofrequency ablation; Treatment outcome