[Pulmonary artery sling: diagnosis by magnetic resonance imaging--one case report].

Pulmonary artery sling is an uncommon congenital vascular anomaly, which may cause significant respiratory morbidity resulting from an external tracheal compression during early infancy. This condition should be considered on finding a mass interposed between the trachea and the esophagus showing an anterior indentation on the esophagograms. The diagnosis is usually made by invasive methods such as bronchography, bronchoscopy, cardiac catheterization, and angiography. Magnetic resonance imaging (MRI) has now become an excellent method for diagnosing cardiovascular anomalies, but the use of MRI as a means of diagnosing pulmonary artery sling is rare. In 1988, Malmgren et al, first reported the use of MRI in three cases. Their findings suggested that two overlaping sets of axial sections might be necessary for depicting the anomaly because different parts of the left pulmonary artery are imaged in different slices. In this paper, we report a diagnostic scan image which utilizes a single axial scan and reveals the pulmonary artery sling arising aberrantly from the right pulmonary artery. We also found (a) when the pulmonary artery sling interposed between the esophagus and trachea; the trachea become stenotic below the upper one-third in LAO equivalent sagittal section; (b) the right pulmonary artery compresses the proximal part of right pulmonary bronchus, and the right upper lobe bronchus arises from the trachea independently in the coronal section. Thus, we conclude that MRI, if available, should be the first choice modality for further examination when a pulmonary artery sling is suggested by conventional radiography.