Figure 8c.  Mirizzi syndrome in a 46-year-old woman with cholangitis. (a) MR cholangiogram reveals a 1.2-cm calculus (arrow) resulting in biliary ductal dilatation. Gallbladder calculi are also seen (arrowheads). (b) MR cholangiogram obtained 5 mm anterior to a shows two calculi in the dilated cystic duct (arrowheads), which parallels the extrahepatic bile duct. The inferior calculus (arrow) corresponds to the calculus seen in a. This calculus eroded through the wall of the cystic duct into the extrahepatic bile duct, bridged the two structures, and resulted in obstruction of the bile duct (Mirizzi syndrome). (c) Endoscopic retrograde cholangiogram demonstrates a calculus in the cystic duct (arrowhead) outlined inferiorly by a small amount of contrast material, as well as the larger, inferior calculus (arrow) causing bile duct obstruction.