History: 66 year-old man with abdominal pain.

Findings: There is a large stone in the gallbladder, air in the biliary tree and in the gallbladder, air-fluid levels and obstructing gallstones in the small bowel.

Diagnosis: Choloenteric fistula with small bowel obstruction secondary to gallstones (gallstone ileus).

Discussion: Gallstones occur in 10 to 20% of the US population. 30 to 50% of people with gallstones have no symptoms. Surgical removal is indicated in symptomatic patients and patients at high risk of acute cholecystitis. Ultrasound is the method of choice for the detection of gallstones and acute cholecystitis. Hepatobiliary scintigraphy is highly sensitive in the diagnosis of acute cholecystitis and common bile duct obstruction. CT and MRI are useful adjunctive imaging modalities and play a key role in the evaluation of adjacent organ disease. Biliary enteric fistula is a complication of chronic cholecystitis, and occurs as long standing gallstones erode through the gallbladder wall, communicating with adjacent small bowel (typically duodenum). This case illustrates small bowel obstruction due to gallstones in a case of biliary enteric fistula.