Mirizzi syndrome is a rare condition of bile duct obstruction caused by an impacted gallstone creating external compression of the biliary duct. It is reported more commonly in Latin America and less commonly in North America and Western Europe, for unknown reasons. Patients age 50-70 years with a history of gallstones (associated with obesity and female sex) are at the highest risk for developing Mirizzi syndrome. The disease has a female-to-male ratio of about 2:1.

Clinical presentation can vary significantly, as some patients present with colicky or persistent right upper quadrant (RUQ) abdominal pain, nausea or emesis, jaundice, fever, or septic shock depending on the degree and location of biliary, and possible pancreatic, ductal obstruction.

Mirizzi syndrome has 2 variants, one involving a large impacted gallstone in the cystic duct or Hartmann pouch and the other involving fistula (cholecystocholedochal) formation. That classification can be further expanded to 4 types that clarify the extent of involvement, erosion, and destruction of the common bile duct.

Lab tests typically reveal elevations in transaminases (aspartate transaminase [AST] / alanine transaminase [ALT]), alkaline phosphatase, gamma glutamyl transpeptidase, and hyperbilirubinemia (primarily direct). Leukocytosis is also commonly seen.

History, physical examination, and labs are helpful in raising clinical suspicion, but confirmatory diagnosis is made via imaging studies. Ultrasound can show obstructed gallstones with intra- and extra-hepatic ductal dilatation without common bile duct dilatation and no gallstones obstructing the common bile duct (poor sensitivity, approximately 8.3%-27%). Computed tomography is of less utility. Magnetic resonance cholangiopancreatography (MRCP) is the gold-standard imaging modality for evaluating the location of obstructing gallstones and ductal dilatation.

However, MRCP is still not a perfect imaging modality. If clinical suspicion is high and lab testing is suggestive of an obstructive jaundice, endoscopic retrograde cholangiopancreatography (ERCP) should be performed for both diagnosis and potentially therapeutic intervention. In many instances, Mirizzi syndrome is discovered intra-operatively during cholecystectomy via retrograde cholangiogram. Treatment varies as the goal is to remove impacted stones and instill biliary ductal patency, requiring the repair of fistulas if present.