A 49 -year-old woman, who previously had been healthy with no significant comorbidities, underwent spinal cord decompression followed by vertebral fusion for severe thoracic spinal stenosis at the level of T9-T10. At the end of surgery, two chest tubes were placed in the left pleural space. These tubes drained straw-colored fluid, the volume of which gradually decreased, and were taken out 4 days later. On the 14th postoperative day, the patient was discharged to home without respiratory symptoms. Her neurologic symptoms of paraparesis were significantly improved. Over the next week, she developed progressive dyspnea (first only on exertion, then persistent) and orthopnea. She had a mild, nonproductive cough but denied constitutional symptoms such as fever, chills, or sweats.