Q. Illustrate Pulmonary Artery Enlargement?

On the PA view, the pulmonary trunk is border forming for a short distance between the aortic knuckle and the left atrial appendage. In children and young adults, (especially women), it often has a convex contour which flattens and reaches the adult pattern by the age of 20 years. On the lateral view, the pulmonary trunk may form the posterior margin of the retrosternal space inferiorly.

When the pulmonary conus enlarges, it forms a smooth convexity in the expected position on the PA view, and encroaches on the lower portion of the retrosternal clear space on the lateral view. On the PA view, nodes or masses at the left hilum or adjacent mediastinum may simulate this appearance. Focal post stenotic dilatation of the pulmonary artery tends to involve the roof of the vessel, and is thus relatively high-placed.