A Rare Case of Cholecystoduodenal Fistula Complicated With Gallstone Ileus and Upper Gastrointestinal Bleeding.

Gallstone ileus is a rare presentation of cholelithiasis, which usually impacts the narrowest part of the bowel, the ileocecal valve. This occurs as a result of a bilioenteric fistula where a gallstone passed through and entered the gastrointestinal tract. It is most commonly encountered in elder patients and predominantly in females.