Accessory Diaphragm Associated with Single Pulmonary Vein in an Asymptomatic Patient: 64-Multidetector CT Findings

A 49-year-old woman with a history of myocardial revascularization surgery presented at the emergency department of a tertiary-care hospital with the complaint of chest pain. After initial clinical, laboratory, and radiographic assessment, a 64-multidetector computed tomography (MDCT) scan was ordered to elucidate the X-ray findings of a linear opacity near the right lung base, apparently parallel to the right hemidiaphragm, and an almost vertical elongated structure on the middle third of the right lung. The abnormalities visible on the X-ray were also depicted on the CT scout image (Fig. 1). Volumetric 64-MDCT acquisition was performed in the axial plane with intravenously injected iodine contrast in association with multiple reformatting techniques such as maximum intensity projection (MIP; Fig. 2a), minimum intensity projection (MinIP), volume rendering (Fig. 2b), and virtual bronchoscopy. The examination showed a thin linear structure that coursed obliquely downward from the right thoracic wall, through the lower-lung parenchyma, and into the right diaphragmatic crus, where it displayed soft-tissue density. The vessels coursing to the basal pyramid merged together through a hiatus within that structure just before splitting into their respective segments. A single pulmonary vein drained into the left atrium; its shape and course resembled the ‘‘scimitar’’ of hypogenetic lung syndrome, although no anomalous pulmonary venous return was identified. The accessory diaphragm is a rare anomaly in which the right hemothorax is portioned into two compartments by a musculotendinous membrane resembling a diaphragm. This malformation is often associated with vascular and airway anomalies [1, 2]. A gap (hiatus) in the accessory diaphragm is usually present to allow the passage of vessels and bronchi to supply this portion of lung. The radiological appearance of this lung portion depends on whether it is aerated, and it is easily mistaken for fibroatelectatic strands on X-rays or CT scans [1, 2].