Contrast-enhanced ultrasound-guided percutaneous microwave ablation of renal cell carcinoma that is inconspicuous on conventional ultrasound

Purpose: This study was designed to determine the safety, effectiveness and feasibility of contrast enhanced ultrasound (CEUS)-guided percutaneous microwave ablation (MWA) of renal cell carcinoma (RCC) that is inconspicuous on conventional ultrasound (US). Materials and methods: A total of 32 RCC nodules in 29 patients (23 men and 6 women) were treated with CEUS-guided percutaneous MWA between January 2010 and September 2014. The median maximum diameter of the nodules was 2.4 cm (interquartile range: 1.8-2.9 cm). The US contrast agent was SonoVue, a second-generation contrast agent. CEUS was applied before the needle was inserted into the tumour, and percutaneous MWA was performed under CEUS-guidance. Results: In total 31 tumours were successfully visualised via CEUS using 1-2 (1.0-2.0 mL) contrast agent injections, and percutaneous MWA was performed under CEUS-guidance. The technical success rate of CEUS-guided percutaneous MWA of RCC was 96.9% (31/32). The mean number of sessions of CEUS-guided percutaneous MWA for each tumour was 1.2 +/- 0.4. The mean duration of energy application for each tumour was 7.3 +/- 2.7 min. All patients were followed up for 3-71 months (median 17 months) to observe the therapeutic effects and complications. The therapeutic effects were assessed at follow-up with computed tomography (CT) or magnetic resonance imaging (MRI) and CEUS. There was no local tumour progression and the technique effectiveness rate was 100% (31/31). The complications rate was 6.5% and the major complications rate was 3.2%. We observed one case of pleural effusion and one case of renal subcapsular haemorrhage after the percutaneous MWA procedures. Conclusion: CEUS-guided percutaneous MWA is a safe, efficient and feasible therapy for patients with RCCs inconspicuous on conventional US.