Use of contrast-enhanced intraoperative ultrasonography during liver surgery for colorectal cancer liver metastases - Its impact on operative outcome. Analysis of a prospective cohort study

Background: Preliminary reports led to discordant conclusions concerning the use of contrast-enhanced intraoperative ultrasonography (CE-IOUS) during surgery for colorectal liver metastases (CLM). The aim of this study was to evaluate the impact of CE-IOUS in patients undergoing surgery for CLM using an advanced preoperative imaging work-up, and well-established reference standards. Materials and methods: Forty-seven consecutive patients underwent liver resection using IOUS and CE-IOUS for CLM. All patients underwent preoperative computed tomography (CT) and magnetic resonance imaging (MRI) within 2 weeks prior to surgery. CE-IOUS was performed by injecting intravenously 4.8 ml of sulphur-hexafluoride microbubbles (SonoVue, Bracco, Italy). Reference standards were histology, and 6-month imaging follow-up. Results: IOUS discovered 43 additional lesions in 20 patients. CE-IOUS found 10 additional lesions not seen at IOUS in four patients, and confirmed all the IOUS findings. Fourteen CLM in 10 patients appeared within 6 months after surgery. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were, respectively: 66%, 0%, 98%, 0% and 65% for CT + MRI; 88%, 100%, 100%, 8%, 88% for IOUS and 93%, 100%, 100%, 13%, 93% for IOUS + CE-IOUS. In nine patients CE-IOUS afforded better definition of tumour margins thus helping in resection guidance. Conclusions: CE-IOUS improves IOUS findings both for detection and for resection guidance. The combination of IOUS and CE-IOUS should be considered routinely in patients operated for CLM.