Optimizing Distal Biliary Stricture Diagnosis: Endoscopic Ultrasonography for Undetected Masses on Cross-Sectional Imaging

Background and study aim: Biliary strictures (BS), especially when associated with undetected masses on magnetic resonance imaging (MRI) or computed tomography (CT), present diagnostic challenges. Termed indeterminate biliary strictures (IBS), these cases necessitate accurate differentiation between benign and malignant causes. Endoscopic ultrasonography (EUS) is an advanced imaging modality with diagnostic and interventional capabilities that can help in better identification of IBS. This study aims to evaluate the accuracy of EUS in identifying the underlying causes of indeterminate biliary strictures (IBS). Patients and Methods: The study included 36 patients with distal common bile duct strictures and undetected masses on CT or MRI. EUS was employed to differentiate between benign and malignant strictures, and the final diagnosis was confirmed through histological examination. Results: EUS demonstrated a sensitivity of 90% and specificity of 71.4% in accurately identifying DBS without a tumor. After six months of follow-up, EUS maintained sensitivity and specificity rates of 87% and 100%, respectively. Malignant strictures were associated with significant weight loss and elevated levels of aspartate aminotransferase (AST), alanine transaminase (ALT), direct bilirubin, cancer antigen 19-9 (CA 19-9), and carcinoembryonic antigen (CEA). Conclusion: In summary, EUS emerged as a dependable diagnostic tool for patients with DBS and undetected masses on cross-sectional imaging, revealing small irregular hypoechogenic masses disrupting duodenal and bile duct layers, potentially indicative of malignancy.