An 87-year-old female with a 10-year history of type 2 diabetes presented with upper abdominal pain, yellow urine, and fever for 5 days. Physical examination showed upper abdominal tenderness without rebound tenderness or muscle guarding. Imaging revealed a liver abscess, distal common bile duct stone, gallbladder stones, and intrahepatic and extrahepatic bile duct dilatation with pneumobilia, suggesting a cholecystoenteric fistula. Ultrasound-guided percutaneous drainage of the liver abscess was performed. Endoscopic examination confirmed a cholecystoduodenal fistula. ERCP revealed common bile duct stones, which were removed via ERC+EST+EPBD+stone retrieval+ENBD . Two days post-procedure, the patient experienced intermittent vomiting of bile-like fluid. Repeat abdominal CT suggested gallstone ileus due to gallstone migration into the small intestine. Surgical removal of the stones was performed due to poor response to conservative treatment. Given her advanced age and poor physical condition, no further treatment was pursued for the cholecystoduodenal fistula. The patient was monitored in the ICU postoperatively and later transferred to a general ward, eventually improving and being discharged.Cholecystoduodenal fistula is an internal fistula between the gallbladder and duodenum. Gallstone ileus, a rare cause of mechanical intestinal obstruction (0.3–0.5% of cases), occurs when gallstones block the intestine after passing through a cholecystoenteric fistula. It is more common in elderly females. Treatment is primarily surgical, including enterotomy for stone removal or combined with cholecystectomy and fistula repair. However, there are few reported cases of gallbladder internal fistula complicating with hepatic abscess. In this case, the patient’s type 2 diabetes likely facilitated retrograde bacterial infection, leading to hepatic abscess formation after the gallbladder internal fistula developed.This case report documents the complete clinical course of a patient who developed gallstone ileus caused by the spontaneous passage of stones through a cholecystoduodenal fistula during hospitalization.