Case report: Primary aortosigmoid fistula − A rare cause of lower gastrointestinal bleeding

INTRODUCTION: A primary aortoenteric fistula (PAEF) is a communication between aorta and the gastrointestinal tract. It is a rare condition that is difficult to diagnose and therefore associated with a high mortality. PRESENTATION OF CASE: We report a rare case of a 66-year old man with an unstable bleeding PAEF. A salvage procedure was performed with a covered stent. Later, a sigmoidectomy was performed with resection of the fistula. Postoperatively, the patient suffered an infection that was treated well with antibiotics and he was discharged two weeks later with complete resolution of the fistula. DISCUSSION: Aortoenteric fistulas are more common secondary to previous vascular surgery of aorta, however, PAEF’s involve the sigmoid in 2%. Seldom, fistulization can be due to diverticulitis that can be difficult to diagnose. CONCLUSION: Retroperitoneal bleeding from the left iliac artery is more common due to a ruptured aneurysm. This case, however, demonstrates a special PAEF formation as a very rare complication of diverticulitis. The pathophysiology of the PAEF is very unique along with the anatomic localization in the sigmoid colon and left external iliac artery.