3 T MR cholangiopancreatography appearances of biliary ascariasis

Aim To evaluate the 3 T MR cholangiopancreatography (MRCP) appearances of biliary ascariasis. Materials and methods Nine patients with a MRCP diagnosis of biliary ascariasis were reviewed. All patients had endoscopic retrograde cholangiopancreatography (ERCP) or surgical confirmation of the disease. Results On thin-slab MRCP imaging, Ascaris worms are clearly demarcated within the biliary tree. All the identified worms demonstrated a characteristic three-parallel-lines appearance. The middle high-signal intensity line is sandwiched between two low-signal intensity lines and they are in turn surrounded by high signal bile. On thick-slab MRCP the worms also show the three-line sign but with less clarity. However, thick-slab MRCP has the advantage of providing three-dimensional ERCP-like images of the pancreaticobiliary system. Conclusion The “three-line” sign appears to be a characteristic sign of biliary ascariasis on 3 T MRCP.