Impact of contrast-enhanced intraoperative ultrasound on operation strategy in case of colorectal liver metastasis

Background: Surgical treatment is the only option for long-term survival in patients with colorectal liver metastasis (CRLM). Contrast-enhanced CT and MRI are usually used for preoperative liver imaging. The initial surgical strategy for liver resection is based upon these findings. Further optimization of the surgical strategy by contrast-enhanced intraoperative ultrasound (CE-IOUS) might further improve the surgical outcome. Purpose: To evaluate the current impact of CE-IOUS with SonoVue (R) on the initial surgical strategy for CRLM. Material and Methods: Eighty-six consecutive patients undergoing open liver resection for CRLM were evaluated retrospectively over a 2.5-year period. The patients underwent 97 operations. Preoperative staging was performed with contrast-enhanced CT in all patients and MRI was available in 66 of 86 patients. CE-IOUS was performed in all patients according to a standardized examination technique. Curved array and linear transducers were used. CRLM were identified in venous phase as hypovascular lesions. CE-IOUS findings were compared with preoperative staging. Results: Combined CT/MRI identified preoperatively 328 CRLM (mean 3.4, range 0-14). Seventy-two additional lesions (18%) were identified in 38 patients during the operation. Intraoperatively 41 additional CRLM in 20 patients were identified by inspection, palpation, and CE-IOUS (10%), and another 31 CRLM in 17 patients were identified by CE-IOUS alone (8%). All additional CRLM detected by CE-IOUS were confirmed by histology if resection was performed. CE-IOUS changed planned operation strategy in 29.9% of operations. A larger resection was necessary in 13.4% of the cases, reduced liver resection was found sufficient in 11.3%, and 5.2% were found inoperable. For patients diagnosed preoperatively with solitary lesions CE-IOUS changed operation strategy in 19% and radical tumor resection would have failed in 4.8% without CE-IOUS. Conclusion: CE-IOUS is essential to ensure optimal and complete tumor resection both in patient with solitary CRLM and multiple metastases.