in his left lower extremity, which suggested an impending rupture of a large CIAA. At the time of admission, the left lower leg edema had worsened and urgent surgery was scheduled. His hemodynamics were stable, with a blood pressure of 129/60 mmHg and a heart rate of 92 beats per minute. Chest radiography showed no pulmonary congestion, and echocardiography showed a left ventricular end-diastolic diameter/end-systolic diameter of 51/32 mm, a left ventricular ejection fraction of 67%, no significant valvular disease, and no evidence of heart failure. A pulsating abdominal mass was palpable in the left lower abdomen and a continuous bruit was heard. Redness, swelling, and pain were observed in the left lower extremity, from the thigh to the toes. A lower extremity duplex scan revealed no mobile deep vein thrombus, but arterial blood flow was observed in the common femoral vein. Contrast-enhanced computed tomography (CT) revealed a left CIAA (72 mm in diameter). Additionally, contrast enhancement of the left common iliac vein (CIV) was observed in the early phase, suggesting an AVF between the CIA and CIV. Owing to the pressure caused by the aneurysm, almost no contrast enhancement was seen in the inferior vena cava (Fig. 1).Urgent surgery was performed via a midline abdominal incision. A retroperitoneal hematoma was observed in the left lower abdomen. Although there was almost no adhesion, the left ureter was compressed by the left CIAA. A cross-clamp was applied to the infrarenal aorta and right CIA. The left internal and external iliac arteries could not be identified because of the presence of the large aneurysm. An additional incision was made in the left groin, and a distal clamp was applied to the common femoral artery (CFA). When the CIAA was opened, a large AVF measuring 40 × 30 mm on cross-section was identified between the left common iliac artery and vein. Furthermore, we found that a fresh thrombus measuring 10 × 40 mm had emerged from within the AVF. Because of the large AVF, it was difficult to control the bleeding; hence, we performed the suture-ligation of the orifice of the left internal iliac artery (IIA) to control the blood from the IIA. The full thickness of the aneurysm wall was then Ruptured abdominal aortic aneurysms and common iliac artery aneurysms (CIAAs) are rarely associated with an arteriovenous fistula (AVF). In such cases, surgery is frequently extremely difficult and the prognosis is usually poor. We report a case of a ruptured CIAA with a common iliac AVF in a 58-year-old male patient who presented with symptoms of severe edema in his left lower extremity. We used an aneurysm wall patch to repair the fistula and successfully reconstruct the common iliac vein, and a bifurcated prosthetic graft for abdominal aortic and iliac artery replacement.