A 70-year-old unconscious man with hospital phobia was transported to our hospital. On arrival, he displayed consciousness disturbance, unstable circulation, and a hypothermic state. Based on the clinical symptoms, the results of whole body computed tomography (CT), and biochemical studies, he was diagnosed with urosepsis (induced by vesico-enteric fistula), hyperglycemic crisis, infectious abdominal aortic aneurysm (iAAA), gallbladder stone-induced pancreatitis, and multiple organ failure. He was treated with supportive therapy. The abdominal magnetic resonance image (MRI) revealed an abdominal aortic aneurysm (AAA) with an inflammatory aortic wall, paraaortic inflammatory lymph node swelling, and periaortic fat inflammation. His consciousness temporarily recovered, but he did not agree to undergo surgery. On day 28, he suddenly collapsed. We present a fatal case of iAAA induced by urosepsis from vesicoenteric fistula and/or acute pancreatitis, complicated by multiple organ failure. In aging societies, physicians should explore not only the cause of disease but also the severity of the pathology and define fatal complications in elderly patients.