ACCESSORY FISSURES OF THE UPPER LOBE OF THE LEFT LUNG - CT AND PLAIN FILM APPEARANCE

OBJECTIVE. The purpose of this study was to assess CT and chest radiog raphic features of accessory fissures of the upper lobe of the left lu ng. MATERIALS AND METHODS. Eighteen accessory fissures of the upper lo be of the left lung were identified on CT scans of 17 adult patients. The collimation was 10 mm in 12 patients and 8 mm in five patients. Ad ditional, thinner sections (1.5-5.0 mm) were available for 12 patients . The segments separated by each fissure were identified by means of t he individual segmental bronchi and vessels. Available chest radiograp hs were correlated with CT studies in 12 patients. RESULTS. The fissur es separated the anterior segment of the left upper lobe from the supe rior segment of the lingula (left minor fissure) in 13 cases (72%), th e superior from the inferior segment of the lingula in three cases (17 %), and the apicoposterior from the anterior segment in two cases (11% ). Ten (56%) of the 18 fissures could be seen only on thin sections. E leven (61%) of the accessory fissures were incomplete. The fissures we re classified into four types: convex laterally (n = 8), convex medial ly (n = 2), anteromedial (n = 5), and transverse (n = 3). On posteroan terior chest radiographs, the accessory fissure was evident in 10 (83% ) of 12 patients. CT studies showed that nine of the 10 fissures seen on radiographs represented a left minor fissure, and the remaining fis sure separated the two segments of the lingula. CONCLUSION. Accessory fissures of the upper lobe of the left lung, as shown by CT, can separ ate any two contiguous segments, are frequently incomplete, and occur in four different configurations. The left minor fissure is the most c ommon of these fissures and the most frequently seen on chest radiogra phs. The ability to recognize accessory fissures of the left upper lob e should help in the segmental and topographic localization of pulmona ry lesions.