VARIATIONS OF THE PLEURAL VERTICAL FISSURE LINE.

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The vertical fissure line of the pleura was described and given its name in 1960, by Davis (1). It is demonstrable roentgenographically as a linear shadow roughly paralleling the chest wall, extending vertically upward from the lateral portion of the diaphragm. Although no reports of this finding have appeared since its first description, the authors have observed it on 26 chest films taken at the UCLA Center for the Health Sciences from 1961 until the present. The importance of the vertical pleural fissure lies in its recognition. The normal major fissure extends from the posterior pleura superiorly to the anterior chest wall inferiorly and generally runs in a plane. While it is seen usually in the lateral projection, in certain persons it is most apparent in a slightly oblique lateral view, which suggests that it is not always located in the coronal plane. Since these fissures can sometimes be seen in several different degrees of minimal obliquity, it may be inferred that the fissure does not lie in a plane at all, but rather in a curved surface. The major fissure has been described as sometimes dividing into two planes at the point of origin of the minor fissure. At postmortem examination, Davis marked the lateral inferior aspect of the major fissure with a wire and showed that it corresponded to the position of the vertical fissure line that was noted on the antemortem chest film. He describes these lines as being associated with congenitally enlarged hearts and as always being on the right. Our series, however, includes one case in which the fissure occurred with no evidence of cardiac enlargement of disease and several in which a fissure line was present on the left as well as on the right. In one of our patients, an area of consolidation was limited by the fissure line, and in another the line was outlined by free pleural fluid. The fissure line can be mistaken for a pneumothorax, as suggested by Davis, though usually it is seen only inferiorly, and not in the apex as would be characteristic of a true pneumothorax. The vertical fissure line is somewhat more evident in the anteroposterior projection than in the postero-anterior, in our experience. Summary In 26 patients a vertical pleural fissure line has been noted. Most of this group suffered from cardiomegaly and were examined in the anteroposterior projection. Almost all were infants or children. One normal adult chest film taken in the postero-anterior projection showed this finding. Although most of the fissure lines were on the right, in several cases there were lines on both sides or on the left side only. Once recognized, vertical fissures are not likely to be mistaken for other more significant abnormalities.