BACKGROUND: Detecting more colorectal liver metastases (CRLMs) during surgery may help optimise strategy and improve outcomes. Our objective was to determine clinical utility (CU) of contrast-enhanced intra-operative ultrasound (CE-IOUS) using sulphur hexafluoride microbubbles during CRLM surgery. METHOD: A prospective phase II trial performed at two comprehensive cancer research centres. Patients operated for CRLMs were eligible and assessable if intra-operative ultrasound (IOUS) and CE-IOUS had been performed and pathological results were available and/or 3-month imaging. CU was defined as the justified change in planned surgical strategy or procedure using CE-IOUS. RESULTS: Out of the 68 patients enrolled, 54 were eligible and assessable. 43 patients underwent pre-operative chemotherapy. The median number of CRLMs was 2 (range, 1-11). Pre-operative staging was performed using MRI. IOUS allowed identification of 45 new CRLMs in 13 (24.7%) patients. Compared to IOUS, CE-IOUS allowed identification of 10 additional CRLMs in 9 (16.7%) patients. Surgery was altered and justified in 4 patients only, leading to a CU rate of 7.70% (95 CI, [3.2, 18.6]). No missing CRLMs were identified by CE-IOUS. CONCLUSIONS: Although the primary endpoint was not met for one protocol violation, secondary endpoints indicate that CE-IOUS has an intermediate added-value for surgeons treating CRLMs. TRIAL REGISTRATION: NCT01880554 (https://clinicaltrials.gov/).Read less <