Gallstone ileus, a complication of chronic cholecystitis, is an uncommon cause of mechanical small bowel obstruction. It occurs when a gallstone passes into the small bowel lumen and impacts to cause mechanical obstruction.Typically present with a background of long history of recurrent right upper quadrant pain, these repeated  attacks of cholecystitis result in adhesion of the gallbladder to the small bowel (usually duodenum) with eventual fistula formation (cholecysto–enteric fistula) and passage of gallstones into the lumen of the bowel. The site of obstruction is usually the terminal ileum because it is the narrowest portion of the small bowel.

Due to the demographics of the population affected (elderly) this condition continues to have a high mortality. Availability of computerized tomography scan have made diagnosis with certainty. Surgery is definitive, with removal of the stone (enterolithotomy), fistula repair, accompanied by cholecystectomy.