PLE-2429

A 67-year-old man is brought to the emergency department 4 hours after the onset of severe midlumbar back pain. He is anxious, pale, and diaphoretic. His temperature is 37.1 C (98.8 F), blood pressure is 105/65 mm Hg, and pulse is 120/min. Examination shows no other abnormalities. X-ray films of the lumbar spine show degenerative disc disease with calcifications anterior to the vertebral bodies. What is the most likely diagnosis?