A life-threatening concern is hemorrhage, which may result from damage to the aorta, iliac arteries or veins in the pelvis. The majority of bleeding due to pelvic trauma is due to injury to the veins. Fluid (often blood) may be detected in the pelvis via ultrasound during the FAST scan that is often performed following traumatic accidents. Should a patient appear hemodynamically unstable in the absence of obvious blood on the FAST scan, there may be concern for bleeding into the retroperitoneal space, known as retroperitoneal hematoma. Stopping the bleeding may require endovascular intervention or surgery, depending on the location and severity.