Routine Preoperative Liver-specific Magnetic Resonance Imaging Does Not Exclude the Necessity of Contrast-enhanced Intraoperative Ultrasound in Hepatic Resection for Colorectal Liver Metastasis

Objectives:To assess the usefulness of contrast-enhanced intraoperative ultrasound (CE-IOUS) during surgery for colorectal liver metastases (CRLM) when gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (EOB-MRI) is performed as a part of preoperative imaging work-up.Background:EOB-MRI is expected to supersede CE-IOUS, which is reportedly indispensable in surgery for CRLM.Methods:One hundred consecutive patients underwent EOB-MRI, contrast-enhanced computed tomography (CE-CT), and contrast-enhanced ultrasound within 1 month before surgery for CRLM. Conventional IOUS and subsequent CE-IOUS using perflubutane were performed after the laparotomy. All the nodules identified in any of the preoperative or intraoperative examinations were resected and were submitted for histological examination, in principle.Results:Preoperative imaging examinations identified 242 nodules; 25 additional nodules were newly identified using IOUS, 22 additional nodules were newly identified during CE-IOUS, and a histological examination further identified 4 nodules. Among the 25 nodules newly identified using IOUS, all 21 histologically proven CRLMs and 3 of the 4 benign nodules were correctly diagnosed using CE-IOUS. Among the 22 nodules newly identified using CE-IOUS, 17 nodules in 16 patients were histologically diagnosed as CRLMs. The planned surgical procedure was modified on the basis of IOUS and CE-IOUS findings in 12 and 14 patients, respectively. The sensitivity, positive-predictive value, and accuracy of CE-IOUS were 99%, 98%, and 97%, respectively. Those values of EOB-MRI (82%, 99%, 83%, respectively) were similar to CE-CT (81%, 99%, 81%, respectively).Conclusions:CE-IOUS is useful in hepatic resection for CRLM, even if EOB-MRI and CE-CT are performed.