MRI of cholangitis: traps and tips

Area of Science:

• Radiology and Medical Imaging
• Gastroenterology
• Hepatology

Background:

• Magnetic resonance imaging (MRI) is crucial for examining bile ducts, but faces several limitations.
• These limitations span technical aspects (spatial resolution, image reconstruction), anatomical variations (flow artifacts, anatomical variants), and semiological interpretation (imprecise terminology).
• Complex biliary diseases like cholangitis, including primary sclerosing cholangitis (PSC), present diagnostic challenges, especially when associated with cholangiocarcinoma.

Observation:

• Technical limitations include reliance on Maximum Intensity Projection (MIP) and native images, T1-weighted sequences, and suboptimal spatial resolution.
• Anatomical considerations involve understanding flow artifacts, air/bleeding within ducts, hepatic artery indentation, and portal biliopathy variants.
• Semiological challenges arise from imprecise descriptive terms inherited from retrograde cholangiography, such as 'string of pearls' or 'dead tree' appearances.

Findings:

• A precise exploration technique using 3D magnetic resonance cholangiography (3D MRC) sequences can circumvent these limitations.
• This technique involves volume analysis, native slices, MIP reconstructions, and heavily T2-weighted and T1-weighted 3D sequences (with or without gadolinium).
• A stereotyped interpretation plan is essential, including assessment of bile duct stenosis/dilatation, intrahepatic calculi, liver parenchyma heterogeneity, liver dysmorphia, portal hypertension signs, and bile duct wall enhancement.

Implications:

• Improved diagnostic accuracy for various bile duct pathologies, including cholangiocarcinoma associated with PSC.
• Standardized imaging protocols and interpretation reduce diagnostic errors and improve patient management.
• Enhanced understanding of biliary anatomy and pathology through advanced MRI techniques.