Contrast-Enhanced Low-Mechanical-Index Endoscopic Ultrasound for the Evaluation of Focal Liver Lesions

Contrast-enhanced low-mechanical-index endoscopic ultrasound (CELMI-EUS) extends the diagnostic capabilities of endoscopic ultrasound by enabling real-time assessment of hepatic microvascularization and perfusion using intravenous ultrasound contrast agents. Owing to its close proximity to the liver and high spatial resolution, CELMI-EUS is particularly suited for the detection and characterization of small or otherwise inconspicuous focal liver lesions. This review summarizes the technical principles of CELMI-EUS, contrast agent usage, vascular phase interpretation, and standardized assessment of benign and malignant focal liver lesions, including the potential and provisional application of CEUS Liver Imaging Reporting and Data System (LI-RADS) terminology in patients at risk for hepatocellular carcinoma, while acknowledging that dedicated validation for CELMI-EUS is lacking. Typical enhancement patterns of common benign lesions such as hemangioma, focal nodular hyperplasia, hepatocellular adenoma, biliary hamartomas, and abscesses are discussed, as well as malignant entities including metastases, hepatocellular carcinoma, and cholangiocarcinoma. In addition, the role of CELMI-EUS in lesion detection, interventional guidance, and its limitations and pitfalls are addressed. Integrated into a multimodality imaging approach alongside transcutaneous CEUS and cross-sectional imaging, CELMI-EUS represents a valuable complementary tool that improves diagnostic confidence and supports optimized management of patients with focal liver lesions.