Background and Purpose: The percentage of small renal tumors being diagnosed has increased at least fivefold in the last 20 years. The question of bow best to treat these lesions remains unanswered. We studied the effectiveness of 'wet' radiofrequency (RF) ablation of renal tissue. Materials and Methods: New Zealand white rabbits (N = 48) underwent a 1- or 2-minute ablation of renal parenchyma with a modified insulated spinal needle capable of infusing saline, measuring temperature and impedance, and delivering RF energy. Animals were followed and examined up to 54 days after surgery. Results: All animals survived for the planned period. Intravenous urograms showed no fistula or urinoma formation and confirmed continued function of the remaining parenchyma. The 1-minute treatments consistently ablated 20% to 25% (average 7 cm) of the tissue, whereas the 2-minute treatments ablated 34% to 36% (average 10 cm). Acutely, there was coagulative necrosis and infiltration of inflammatory cells. Chronically, there were well-demarcated lesions with complete effacement of the tubular epithelium and destruction of the glomeruli. Conclusion: Wet radiofrequency ablation with a liquid electrode can reproducibly create large lesions safely and quickly. The technique may soon become an alternative, minimally invasive therapy for small renal tumors.
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