The cystic duct: Normal anatomy and disease processes

The cystic duct can be depicted with a variety of imaging modalities but is optimally visualized with direct cholangiography or magnetic resonance cho langiopancreatography. Nevertheless, unrecognized anatomic variants of the cystic duct may cause confusion on imaging studies and complicate subsequen t surgical, endoscopic, and percutaneous procedures. Primary entities invol ving the cystic duct include calculous disease, Mirizzi syndrome, cystic du ct-duodenal fistula, biliary obstruction, neoplasia, and primary sclerosing cholangitis. The cystic duct may also be secondarily involved. by adjacent malignant or inflammatory processes. Postoperative alterations are seen af ter liver transplantation or cholecystectomy when a portion of the cystic d uct is left behind as a remnant. Recognized postoperative complications inc lude retained cystic duct stones, cystic duct leakage, and malposition of T tubes in the remnant. Pitfalls encountered in cystic duct imaging include pseudocalculous defects from overlap of the cystic duct and common bile duc t, underfilling of the cystic duct during direct cholangiography, and admix ture defects at the cystic duct orifice. Pseudomass or pseudotumor defects may result from an impacted cystic duct stone or from a tortuous, redundant cystic duct. Familiarity with the imaging appearance of the normal cystic duct, its anatomic variants, and related disease processes facilitates accu rate diagnosis and helps avoid misinterpretation.