Background: The present study was designed to evaluate the role of intraoperative ultrasound (IOUS) in intrahepatic staging and the impact on surgical strategy for patients with colorectal liver metastases (CRLM). Methods: The study included 515 patients who had undergone liver resection for CRLM at two tertiary care referral centers. Data from a prospectively collected database were retrospectively analysed. Early intrahepatic recurrence was assessed at 3 and 6 months after resection and was considered as residual disease undetected by IOUS. Performance of imaging modalities was compared by analysis of studies on individual patients. Results: A total of 1,370 liver metastases were detected preoperatively with a median of 3 imaging modalities. MRI and PET were performed in 51 and 42 % of the patients, respectively. Median number of days between last imaging and surgery was 18. Contrast-enhanced IOUS was performed in 136 patients (26.4 %). Intraoperatively, 293 new nodules were found in 132 patients: on histology 280 were CRLM (17.6 %). Surgical strategy was changed in 140 patients (27.2 %). On multivariate analysis synchronous and bilobar metastases ≥3 in number, BMI ≥30, and time between last imaging and surgery longer than 18 days resulted in predictive factors indicating new nodules detected by IOUS. Early intrahepatic recurrences were 3.7 and 7.9 % at 3 and 6 months. Performance of CT, MRI, FDG-PET, and intraoperative staging was compared: sensitivity was 63.6, 68.8, 53.6, and 92 % and specificity was 91, 92.3, 95.8, and 97.8 %, respectively Conclusions: The use of IOUS continues to be mandatory for correct staging of patients with CRLM undergoing liver resection.
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