The differential diagnosis for patients presenting with concurrent cholecystitis and hematemesis is limited and includes cystic artery pseudoaneurysm and fistula between the cystic or hepatic arteries and gallbladder. Additionally, duodenal ulcer disease has been reported to cause both gastrointestinal bleeding and bilioenteric fistulas, though few cases have been reported of cholecystoduodenal fistula presenting with concurrent hematemesis, jaundice, and cholecystitis. An 84-year-old woman with diabetes, hyperlipidemia, and back pain on chronic NSAID therapy presented with hematemesis after a two-day history of post-prandial epigastric pain, vomiting, and fevers. Exam revealed jaundice and tenderness with guarding in the right upper quadrant of the abdomen. Shortly after presenting, she developed massive hematemesis and was intubated. Initial labs revealed a leukocytosis of 18, hemoglobin 6.9, AST 89, ALT 54, total bilirubin 5.8 (direct 4.9), and alkaline phosphatase 211. A CT scan revealed cholecystitis as well as gas in the gallbladder, cholelithiasis, and mild intrahepatic biliary dilatation. Subsequent angiography was negative for active extravasation, pseudoaneurysm, and arterial abnormalities. Upper endoscopy revealed a 15mm ulcer in the duodenal bulb with overlying clot. Removal of this clot revealed a defect, and injection of contrast under fluoroscopy demonstrated that the ulcer base extended into the gallbladder, confirming a cholecystoduodenal fistula. ERCP was performed revealing filling defects in the lower third of the common bile duct, and a biliary stent was placed. She improved clinically, with plans for future cholecystectomy and fistula repair. Amongst bilioenteric fistulas, cholecystoduodenal fistulas are most common, with choledochoduodenal fistulas comprising only one-fourth of cases. Up to 90% of bilioenteric fistulas result from cholelithiasis, while only 5% result from duodenal ulcer disease. The most common presentation is with cholangitis, though it occurs in less than 10% of patients; presentation with obstructive jaundice or gastrointestinal bleeding is exceedingly rare. Pneumobilia on imaging is a hint as to the diagnosis and is seen in 14-22% of cases. It is vital for clinicians to consider this diagnosis when such clinical signs are present, as complications from delay in diagnosis can be serious, and management differs from other etiologies of upper gastrointestinal bleeding and gallbladder disease.Figure: CT scan of the abdomen demonstrating gas in the gallbladder.Figure: Endoscopic appearance of the cholecystoduodenal fistula tract.Figure: ERCP revealing filling defects in the common bile duct.