Follow-up of renal masses after cryosurgery using computed tomography; enhancement patterns and cryolesion size

Abstract

To describe the characteristics of cryolesions as seen on computed tomography (CT), for size and enhancement patterns, and to assess correlations between these imaging findings and histopathological diagnosis, as in renal cryosurgery the tumour is ablated in situ and the follow-up is mainly based on imaging. Forty-seven patients with a suspicious renal mass of <or=4 cm had a laparoscopic cryoablation; biopsies were taken during surgery and after cryosurgery the follow-up was by CT at 3, 6, 9, 12, 18, 24, 30 and 36 months. One radiologist reviewed the CT images, measured the diameter of the cryolesions, and described enhancement patterns. In 26 patients there were follow-up CT data for >or=6 months; the mean (range) tumour size was 2.4 (1.3-3.8) cm and the mean follow-up was 17.2 (6-36) months. One cryolesion showed residual tumour on the first scan after treatment. Of the other 25 cryolesions, 20% showed rim enhancement after treatment, including one also showing focal enhancement. This enhancement had disappeared within 6 months. All cryolesions showed non-enhancing infiltration of the perirenal fatty tissue. The mean diameter of the cryolesions decreased by 38% in 12 months. These results were independent of histopathological diagnosis. Using CT, there is rim enhancement in 20% of cryolesions in the first 6 months after renal cryoablation, with a mean reduction in the diameter of the cryolesions of 38% in the first year. These findings are independent of the histopathological diagnosis.