The azygos vein sometimes merges abnormally across the right upper lobe of the lung and it hangs at the lower edge of a membranous septum, called the meso-azygos. The septum invaginates the lobe and makes a fissure. The smaller medial part of the right upper lobe is called an azygos lobe. A 16-year-old male patient was diagnosed with right-sided pneumothorax, and a closed thoracostomy was done in the emergency room. During elective wedge resection including the bulla, the meso-azygos, abnormal azygos vein, and azygos lobe were detected. We reviewed the computed tomography images and found that the azygos lobe had re-expanded laterally, not medially, to the meso-azygos after the closed thoracostomy in the emergency room. The patient had been diagnosed with left-sided pneumothorax a year ago, and no one noticed the azygos lobe at that time. We report the intraoperative findings and comparative images of a migratory azygos lobe.
Keywords: Azygos lobe; Case report; Computed tomography; Spontaneous pneumothorax; Video-assisted thoracic surgery.