Introduction: Gastrointestinal bleedings are often a manifestation of ongoing disease processes within the GI tract. Thanks to widely available endoscopic and imaging examinations, they can be quickly and accurately diagnosed. Case report: A 68-year-old male patient was admitted to the Department of Internal Diseases due to lower GI bleedings. The patient’s history revealed endovascular aneurysm repair and right coronary artery drug-eluting stent angioplasty. The patient underwent multiple diagnostic procedures. Once the potential site of bleeding had been found and emergency exploratory laparotomy performed, visualization was enabled of the location of an aortoileal fistula caused by a prosthesis decubitus. Conclusions: In patients with aortic or aortoileal prostheses and symptoms of acute haemorrhage, an aortoenteric fistula should always be considered. Diagnosis should be based on complementary endoscopic and radiological examinations.