Contrast-Enhanced Ultrasound for the Evaluation of the Cryolesion After Laparoscopic Renal Cryoablation: An Initial Report.

Purpose: Stringent radiological follow-up is essential after renal tumor ablation. Drawbacks of postablation follow-up by contrast-enhanced computed tomography (CECT) are the associated ionizing radiation and nephrotoxic contrast agent. Contrast-enhanced ultrasound (CEUS) has shown potential to demonstrate microvasculature without using either ionizing radiation or toxic contrast agent. We assessed the concordance of enhancement patterns of CEUS and CECT/MRI in cryolesion assessment after laparoscopic renal cryoablation (LCA). Methods: From 01/2006 to 01/2009, a CEUS was performed before and after LCA (3 and 12 months) in addition to regular CECT/MRI. Using an enhancement score (0=no enhancement, 1=rim enhancement, 2=diffuse enhancement, 3=localized enhancement, 4=no enhancement defect), the cryolesion was assessed by both modalities, and concordance of enhancement score was assessed. Results: In total, 45 tumors were included (29 biopsy proven renal cell carcinoma (RCC), mean size 2.66 cm). One cryoablation failed, resulting in a nonenhancing cryolesion apart from the persisting renal tumor. There were no postablation recurrences during the study period. Pre-LCA: Both modalities were available in 26 cases. In 20 out of 26, there was concordance of enhancement score (77%, all cases score 3 or 4). Three months: Both modalities were available in 32 cases. Enhancement score corresponded in 23 out of 32 cases (72%). Seven cases showed enhancement on CECT/MRI ('1' in six cases, '4' in one case) with enhancement score '0'on CEUS. Two cases showed enhancement on CEUS without enhancement on CECT/MRI (specificity 92%, negative predictive value [NPV] 77%). Except one case, all enhancement resolved on subsequent imaging. Twelve months: Both modalities were available in 21 tumors. Enhancement score corresponded in 19 out of 21 cases (91%). Two cases showed enhancement on CEUS without enhancement on CECT/MRI (specificity 90%, NPV 100%). Conclusion: This pilot study shows that CEUS is a safe imaging technique with high concordance of enhancement score between CEUS and CECT/MRI. While cross-sectional imaging seems sensible to demonstrate successful ablation at first follow-up, CEUS might be used to diminish the burden of contrast-enhanced cross-sectional imaging in the long-term follow-up. [ABSTRACT FROM AUTHOR]