Which of the following is an etiological factor in Mirizzi's syndrome?

Mirizzi's syndrome refers to obstruction of common hepatic duct resulting from compression by a gallstone impacted in the cystic duct. Two types of Mirizzi's syndrome are: Type I : Hepatic duct is compressed by a large stone impacted in the cystic duct or Haman's 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.