The most common site of intestinal abstruction in gallstone ileus is

.GALLSTONE ILEUS is a type of acute intestinal obstruction, often seen in elderly and is due to blockage by a bolus or mass of gallstones which commonly enter the intestine through cholecystoduodenal fistula or rarely through cholecystointestinal or -gastric fistulas .Gallstones in the gallbladder | Cholecystitis | Suppuration and adhesion over the duodenal wall | Communication of gallbladder into the duodenum | Gallstones pass into the duodenum forms a bolus ('Rolling stone gather mass') | Blocks narrow pa in the ileum. | Gallstone ileus ref:SRB&;S manual of surgery,ed 3,pg no 594