Comparison of laparoscopic ultrasound and liver-specific magnetic resonance imaging for staging colorectal liver metastases

Background Intraoperative liver ultrasound appears superior to liver-specific contrast-enhanced magnetic resonance imaging (MRI) to stage colorectal liver metastases (CRLMs). Most of the data come from studies on open surgery. Laparoscopic ultrasound (LUS) is technically demanding and its reliability is poor investigated. Aim of the study was to assess the accuracy of LUS staging for CRLMs compared to MRI. Methods All patients with CRLMs scheduled for laparoscopic liver resection (LLR) between 01/2010 and 06/2019 who underwent preoperative MRI were considered for the study. LUS and MRI performance was compared on a patient by patient basis. Reference standards were final pathology and 6 months follow-up results. Results Amongst 189 LLR for CRLMs, 146 met inclusion criteria. Overall, 391 CRLMs were preoperatively detected by MRI. 24 new nodules in 16 (10.9%) patients were found by LUS and resected. Median diameter of new nodules was 5.5 mm (2-10 mm) and 10 (41.6%) were located in the hepatic dome. Pathology confirmed 17 newly detected malignant nodules (median size 4 mm) in 11 (7.5%) patients. Relationships between intrahepatic vessels and tumours differed between LUS and MRI in 9 patients (6.1%). Intraoperative surgical strategy changed according LUS findings in 19 (13%) patients, requiring conversion to open approach in 3 (15.8%) of them. The sensitivity of LUS was superior to MRI (93.1% vs 85.6% whilst specificity was similar (98.6% MRI vs 96.5% LUS). Conclusions Laparoscopic liver ultrasound improves liver staging for CRLMs compared to liver-specific MRI.