Primary aorto-enteric fistula diagnosed by double-balloon endoscopy.

A primary aorto-enteric fistula (PAEF), rarer than a secondary aorto-enteric fistula, is a direct rupture of the bowel by an abdominal aortic aneurysm (AAA). More than 54% of cases were in the duodenum, while jejunum and ileum were affected in only 15% of cases. An 82-year-old woman with hematemesis and hematochezia was admitted to our hospital emergently. Upper and lower endoscopies did not reveal the source of bleeding. We performed an urgent antegrade double-balloon endoscopy, revealing a submucosal tumor-like protuberance with an ulcer in the jejunum. These findings raised suspicion by PAEF. Subsequent computed tomography showed free air near the AAA, confirming PAEF as the hemorrhage source. An abdominal aortic stent graft was implanted, followed by laparotomy. An adhesion between the AAA and small intestinal wall was found. Postoperative recovery was uneventful, with no recurrence observed. This case underscores the importance of considering PAEF as a potential diagnosis in patients with gastrointestinal bleeding and a history of AAA. Endoscopists should be aware of submucosal tumor such as in this case to avoid misdiagnosing PAEF, as diagnosis and intervention are crucial for favorable outcomes.