Fatal ureteral bleeding is rare among elderly individuals. One cause of bleeding can be a fistula between the arteries and urinary organs, such as a common iliac arterio-ureteral fistula. However, the clinical presentation of fistulas can vary. As microscopic hematuria can be an initial finding, detecting the fistula without gross hematuria may be difficult. Here, we report a case of microhematuria that progressed to massive hematuria caused by a common iliac arterio-ureteral fistula. The patient was an 86-year-old man with a chief complaint of cardiopulmonary arrest. He was resuscitated in the previous condition. He had microscopic hematuria. One month later, the patient underwent rehabilitation. He was in hemorrhagic shock with massive hematuria. Further investigation revealed a right common iliac arterio-ureteral fistula. This case demonstrates the importance of investigating anemia in the elderly, including anemia of urinary origin, despite it being rare.