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A 3-year-old boy was scheduled for a modified Blalock-Taussig shunt (MBTS) on account of tetralogy of Fallot. A right posterolateral thoracotomy was used. On entering the chest, a “fourth lung lobe” was found (fig 1) medial to a pleural fold extending from the apex of the right hemithorax towards the hilum of the lung with the azygos vein lodged in the lower free border of this “pleural mesentery” (fig 2). These findings were consistent with a pulmonary azygos lobe and its associated four-layered pleural fold referred to as the mesoazygos. The mesoazygos was resected together with the azygos vein to gain access to the mediastinum and the MBTS was successfully performed. Recovery was uneventful.
A pulmonary azygos lobe is usually an incidental finding in cadaver dissections and chest radiography. Its bronchial supply is derived from a branch of the upper lobe bronchus and not as a separate branch from the right main bronchus. Therefore, it is not an additional or fourth lobe. The surgical importance of this anomaly is the restricted access to the mediastinum and to the azygos lobe, and the hazards this poses during surgery and especially during video-assisted thoracoscopic surgery.1,2
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Competing interests: none.
Patient consent: Patient/guardian consent was obtained for publication.