Normal left atrium: appearance in children on frontal chest radiographs

The right lateral border of the left atrium can be seen in the anteroposterior radiographs of healthy children. Five hundred forty-three frontal radiographs, mostly of children, were reviewed, and the right lateral border of the left atrium was visualized in 30%, although it was very prominent in only 2.5% of cases. In a comparison of frontal angiocardiograms with plain chest radiographs, the shadow was demonstrated to be the lateral or inferior wall of the left atrium. Entities that simulate the left atrial shadow are presented, and ways to distinguish normal appearance from abnormalities are discussed.