Pitfalls in MR cholangiopancreatographic interpretation

Magnetic resonance (MR) cholangiopancreatography (MRCP) is widely used in t he evaluation of pancreatobiliary disorders. However, numerous related pitf alls may simulate or mask pancreatobiliary disease. Maximum-intensity-proje ction (MIP) reconstructed images completely obscure small filling defects a nd may demonstrate respiratory motion artifacts. T2 weighting may vary with different MR imaging sequences and influence MRCP findings. Incomplete ima ging may create confusion regarding ductal anatomy or disease. Furthermore, MRCP yields only static images and thus may fail to depict various anomali es. Limited spatial resolution makes differentiation between benign and mal ignant strictures with MRCP alone extremely difficult. Susceptibility artif acts may be caused by metallic foreign bodies or gastric-duodenal gas. Flui d accumulation may produce a pseudolesion or pseudostricture, although chan ging the imaging angle or section thickness may be helpful. Pneumobilia may be misinterpreted as bile duct stones, and true stones may be overlooked. Pulsatile vascular compression can cause pseudo-obstruction of the bile duc t. Use of both source and MIP reconstructed images obtained from different angles can help avoid cystic duct-related pitfalls. Repeat MRCP or conventi onal MR imaging can help avoid pitfalls related to the periampullary region . Segmental collapse of the normal main pancreatic duct may be misinterpret ed as stenosis, but administration of secretin is helpful. An awareness of these pitfalls and possible solutions is crucial for avoiding misinterpreta tion of MRCP images.