Radiofrequency ablation of the kidney: acute and chronic histology in porcine model

Objectives. To our knowledge, the chronic histopathologic effects of radiofrequency ablation (RFA) of renal parenchyma have not been extensively documented. In this study, we report the light and electron microscopic features of renal RFA in acute and chronic porcine models. Methods. Eleven animals underwent renal RFA of the lower pole kidney bilaterally. RFA was performed laparoscopically in 6 acute animals and percutaneously in 5 chronic animals. Acute animals were killed immediately following surgery. One chronic animal each was killed on postoperative day 3, 7, 14, 30, and 90. Histopathologic evaluation of all renal tissue specimens was carried out with light and electron microscopy. Results. Acutely, the renal radiolesion appeared as a yellowish white, well-circumscribed, necrotic area on gross examination, with evidence of extensive coagulative necrosis and marked inflammation on microscopic examination. From day 1 through 90, light and electron microscopy revealed evidence of progressive, irreversible cell death and necrosis with diminishing inflammatory response in the glomeruli, tubules, and renal interstitium. RFA lesions underwent gradual spontaneous resorption of the necrotic area with ultimate autoamputation. Conclusions. RFA results in necrosis of the ablated renal parenchyma.