An 81 Year Old with Back Pain.

You see an 81-year-old man in the emergency department. He has been troubled by abdominal and back pain that has been worsening over the last two days. He has smoked 20 cigarettes a day for the last 60 years. On examination his heart rate is 110 beats per minute and his blood pressure is 130/80 mmhg. He is tender over the central abdomen and you feel a pulsatile mass above the umbilicus. You request a CT scan of the abdomen.