1. To discuss and illustrate the spectrum of appearance of post ablation changes of renal tumors, and evolution of CT and MRI appearance of successful RF ablation and cryoablation. 2. To discuss and illustrate signs of tumor recurrence after RF ablation and cryoablation.

Radiofrequency ablation and cryoablation are increasingly used as minimally invasive treatments for renal malignancies. Accurate assessment of lesions on imaging studies after these procedures is essential to evaluate the adequacy of treatment and guide further management. Usually, immediately after ablation, the lesions appear larger than the original mass, and on follow-up exam, are seen as focal masses without contrast enhancement which frequently decrease in size. Linear circumferential density in the perirenal fat is commonly seen after RF ablation. Intravenous contrast is essential to evaluate possible residual or recurrent tumor. This presentation will discuss and illustrate the spectrum of appearance of post ablation changes of renal tumors. Evolution of CT and MRI appearance of successful RF and cryoablation changes, and examples of tumor recurrence are discussed and illustrated. Signs of tumor recurrence include development of nodular enhancement and increase in lesion size.