Imaging in localized intrahepatic bile duct dilatation: a pictorial review of diagnostic and differential approaches.

Localized intrahepatic bile duct dilatation (LIBD) is a prevalent radiological finding characterized by a variety of etiologies, including congenital anomalies, inflammatory conditions, hepatolithiasis, and neoplastic lesions. Accurate differential diagnosis of diseases associated with LIBD is crucial for formulating appropriate treatment strategies and improving patient prognosis. This review provides a comprehensive overview of the definitions, etiologies, clinical symptoms, and key imaging features of common diseases associated with LIBD. Furthermore, it proposes a structured approach for differential diagnosis. By integrating imaging findings with clinical and laboratory data, this approach aims to improve diagnostic accuracy and assist radiologists in making optimal clinical decisions. KEY POINTS: Question LIBD has diverse etiologies and overlapping imaging patterns, but a practical, standardized radiological framework for differential diagnosis remains lacking. Findings This pictorial review summarizes characteristic CT/MRI findings of common LIBD-associated diseases and establishes a stepwise diagnostic approach integrating obstruction points, morphology, and clinical information. Critical Relevance Statement By combining specific imaging patterns with clinical context, this review provides a practical differential diagnostic framework that may improve diagnostic confidence, guide further evaluation, and facilitate earlier detection of malignant transformation in LIBD.