INTRODUCTION: The following case highlights a rare cause of biliary duct obstruction from food impaction of a large duodenal diverticulum containing the ampulla. CASE DESCRIPTION/METHODS: A 74-year-old woman presented with abdominal pain. The patient reported acute onset of epigastric abdominal pain on the morning of presentation. Laboratory values were notable for an alkaline phosphatase of 807 U/L, an aspartate aminotransferase of 948 U/L, an alanine aminotransferase of 1245 U/L, and a total bilirubin of 3.7 mg/dL. CT abdomen and pelvis demonstrated marked intrahepatic and extrahepatic biliary ductal dilation with a common bile duct of 19 mm, as well as a 5 cm periduodenal cystic lesion containing a soft tissue density suggestive of a duodenal diverticulum, although the cystic lesion did not opacify with oral contrast despite the duodenal lumen containing contrast. An endoscopic retrograde cholangiopancreatography (ERCP) was performed. Once the duodenoscope was advanced into the duodenum, the ampulla was not identified, however a large diverticulum with impacted, solid food was seen. Multiple attempts were made to break the bezoar into smaller pieces with only partial success. The ampulla was thought to be entirely located within the diverticulum and was unable to be identified due to the obstructing bezoar, therefore, the ERCP was aborted. The patient underwent a repeat ERCP four days later. The food debris had partially cleared and the major papilla was seen on the rim of a large duodenal diverticulum. No biliary strictures or stones were seen and a plastic stent was successfully placed into the common bile duct. DISCUSSION: This case illustrates an uncommon presentation of a common medical problem. Approximately 75% of duodenal diverticula are located in the second portion of the duodenum and can be described as periampullary, if originating within 2 to 3 cm from the ampulla, or ampullary if containing the papilla. The true prevalence of periampullary or ampullary diverticula is not known, however, it is suggested that the prevalence ranges from 0.16 to 22%. Most duodenal diverticula are found incidentally on imaging or endoscopic examinations and are oftentimes asymptomatic, however complications can occur. Common complications include diverticulitis, hemorrhage, perforation, as well as obstruction, as seen above. This case demonstrates the possible, albeit rare, complications of duodenal diverticula and the need for awareness amongst gastroenterologists to avoid misdiagnosis and prompt treatment.