Cholecystoduodenal fistula (CDF) is a rare complication of gallbladder disease. Clinical presentation is variable, and preoperative diagnosis is challenging due to the non-specific symptoms of CDF. We discuss a 61-year-old male with a history of atrial fibrillation who presented with severe abdominal pain out of proportion to exam. The patient was diagnosed promptly and successfully managed non-operatively. This case presentation emphasizes the need to maintain a broad differential diagnosis for abdominal pain out of proportion to exam, with the possibility of a biliary-enteric fistula as a possible cause. It also stresses the importance of a multimodality imaging approach to arrive at a final diagnosis.