The radiographic evolution of radio frequency ablated renal tumors.
OBJECTIVE
Radio frequency ablation (RFA) of renal tumors is a relatively new technology. Few groups are familiar with the posttreatment appearance of these lesions and how they differ from cryoablated renal masses. We describe the evolution of the appearance of these lesions on followup contrast enhanced (CE) computerized tomography (CT).


METHODS
A total of 64 consecutive renal tumors treated with RFA from April 2000 to September 2003 for which posttreatment CE-CT was done were included in this study. CE-CT was reviewed at 6 weeks, 3 months, 6 months and every 6 months thereafter to determine the characteristic features and evolution of these lesions.


RESULTS
Renal tumors were treated with CT guided percutaneous (34), laparoscopic (28) or open (2) RFA. At a median followup of 13.7 months (range 6 weeks to 29 months) 62 RFA lesions demonstrated an absence of contrast enhancement on CE-CT. Treated endophytic tumors developed a low density, nonenhancing, wedge-shaped defect with fat infiltration seen between the ablated tissue and normal parenchyma. Treated exophytic tumors retained a configuration similar to that of the original with a lack of contrast enhancement and minimal shrinkage. Percutaneous treated lesions developed a peritumor scar or halo that demarcated ablated and nonablated tissue (perirenal fat). Persistent tumor was marked by contrast enhancement within the ablation borders of the original mass in 1 case, whereas tumor recurred after initial successful ablation with an enhancing nodule in 1.


CONCLUSIONS
The radiographic features and evolution of radio frequency ablated renal tumors are unique. Successfully treated tumors demonstrated no contrast enhancement, minimal shrinkage and occasional retraction from normal parenchyma by fat infiltration.
Matsumoto
Edward D
ED
Clinical Center for Minimally Invasive Urologic Cancer Treatment, Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9110, USA.
Watumull
Lori
L
Johnson
D Brooke
DB
Ogan
Kenneth
K
Taylor
Grant D
GD
Josephs
Shellie
S
Cadeddu
Jeffrey A
JA
D018262:Adenocarcinoma, Clear Cell / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery*; D017115:Catheter Ablation; D003452:Cryosurgery; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery*; D011856:Radiographic Image Enhancement; D014057:Tomography, X-Ray Computed