The superolateral major fissures.

In a review of more than 1,000 posteroanterior views of normal adult chests, a curving contour that relates to the major fissure laterally along the superior segment of the lower lobe was identified in 14%. The contour, which was more often seen as an edge rather than a line, was noted only on the right in 4%, only on the left in 6%, and on both the right and the left in 4% of patients. This publication discusses various characteristics of the curving contour, evidence that relates the contour to the major fissure, and the mechanism of production of the curving contour when seen as an edge. Also presented are some clinical examples illustrating the usefulness of understanding this feature of radiographic anatomy.