Limitation for performing ultrasound-guided radiofrequency ablation of small renal masses

Purpose: To evaluate which factor is involved in limiting ultrasound (US)-guided radiofrequency (RF) ablation of small renal masses. Materials and methods: Twenty-five patients with 31 renal masses underwent image-guided RF ablation. If a lesion was visible on US, US-guided RF ablation was performed. If a lesion was invisible on US or if the lesion was incompletely ablated or recurred following US-guided RF ablation, CT-guided RF ablation was performed.We analyzed the various factors which were involved in US-guided RF ablation. Results: Of 31 masses, thirteen were US-visible lesions and underwent US-guided RF ablation whereas thirteen were US-invisible lesions and thus underwent CT-guided RF ablation. The remaining five lesions were US-visible but needed additional CT-guided RF ablation, due to incomplete ablation (n = 4) or recurrence (n = 1); these renal masses (3.1±1.0 cm) were significantly larger than those (1.8±0.6 cm) ablated with US alone (p < 0.05). Steam bubbles (4.4cm±0.7 cm) of the masses requiring additional CT-guided RF ablation were significantly larger than those (2.9cm±0.7 cm) of the tumors completely ablated with US alone in size (p < 0.05). Conclusions: US-invisibility, lesion size, and steam bubbles may limit to perform US-guided RF ablation of small renal masses.