<prompt> Which of the following is an etiological factor in Mirizzis syndrome?Gall bladder stone compressing common hepatic ductGall bladder carcinoma invading IVCGall bladder stone causing cholecystitisPancreatic carcinoma  <response>: Mirizzis syndrome refers to obstruction of common hepatic duct resulting from compression by a gallstone impacted in the cystic duct. Two types of Mirizzis syndrome are: Type I : Hepatic duct is compressed by a large stone impacted in the cystic duct or Hamans pouch. Type II: Calculus has eroded into the hepatic duct to produce a cholecystocholedochal fistula. Investigations: Ultrasonography reveals gallstones with a contracted gallbladder and moderate intrahepatic ductal dilatation with normal extrahepatic biliary anatomy. 