Case of the Month

Right upper quadrant pain and jaundice 

Diagnosis: Mirizzi syndrome 

Investigation

Right and Middle images: Coronal T2 fat saturated sequence and heavily T2 weighted coronal thick slab image showing a large stone lodged in the cystic duct with a fistula between the cystic duct and common hepatic duct. The intrahepatic ducts are dilated. 

Left image: Axial FIESTA sequence in another patient demonstrating a stone lodged in the cystic duct with thickening of the duct walls and adjacent soft tissue thickening. 

Discussion

Mirrizi syndrome describes obstruction of the extrahepatic bile duct by a stone impacted in the neck of the gallbladder, and the associated inflammatory thickening and later scarring that spreads from the gallbladder to the common hepatic or common bile duct.  Obstruction usually occurs high within the duct, proximal to the gall bladder neck. In its more advanced stages, a fistula can form between the gallbladder neck and bile duct. 

The diagnosis can be suspected when imaging demonstrates a gallstone in the neck of the gallbladder and intrahepatic and proximal biliary dilation in the absence of dilation of the distal bile duct. CT demonstrates the anatomy well, but not all gallstones are visible on CT and their presence needs to inferred or confirmed by alternative imaging modalities.  

The main alternative diagnosis is stone within the bile duct itself.  Unfortunately neither ultrasound nor CT can reliably exclude a bile duct stone.  Magnetic resonance cholangiopancreatography (MRCP) overcomes these shortfalls and is the modality of choice for investigating suspected gallstone-related biliary obstruction. Not only can it confirm the presence of a stone and associated inflammatory thickening of the gall bladder neck, it can exclude stones in the bile duct as the cause of biliary dilation, demonstrate the site of obstruction of the bile duct relative to the gallbladder neck and help assess potential fistulas between the bile duct and gallbladder. 

Mirizzi syndrome is relatively uncommon.  Choledocholithiasis is the most common cause of biliary obstruction in the setting of known gallstone disease.