Large gallstones could erode through gallbladder wall to nearby structures, causing fistulas, gastric outlet obstruction and gallstone ileus. They typically occur in elderly patients with comorbidities carrying therapeutic challenges. We present a case of a middle-aged woman who was thought to have symptomatic cholelithiasis. Extensive adhesions precluded safe cholecystectomy. While hepatobiliary iminodiacetic acid scan and magnetic resonance imaging with cholangiopancreatography (MRI-MRCP) failed to visualize the gallbladder, computed tomography (CT) was consistent with cholecystoduodenal fistula. A very large gallstone was seen endoscopically in the duodenum, which was broken down into pieces using a large stiff snare.