Variability of the pulmonary oblique fissures presented by high-resolution computed tomography

The purpose of the study was to evaluate the radiological anatomy of oblique fissures (OFs) on high-resolution computed tomography (HRCT) scans. We retrospectively reviewed HRCT scans of 144 patients with normal lung parenchyma. The uppermost level of OFs with respect to the ribs, configuration (concave, straight, convex and others), orientation (medial or lateral facing), rotation and completeness of OFs were recorded. The most cranial level of the left OF was seen between the third and sixth ribs, and all but one were seen above or at the same level as the right OF. The uppermost extent of the OF was between the third and fourth intercostal space and seventh rib on the right lung. Only 2.2% of the right and 1.6% of the left OFs followed a parallel course to the ribs. The configuration of the OFs was generally concave in the upper zones (85.8% on the right and 72.1% on the left) and convex in the middle and lower lung zones (79.3% on the right and 73.9% on the left); 62.5% of the right and 59.7% of the left OFs were incomplete. Suprahilar portions of both OFs (98.9% on the right and 96.7% on the left) and the infrahilar portion of the right OF (54.2%) were generally facing laterally, whereas the infrahilar portion of the left OF was facing medially (80.9%). Angles of the MFs differed at the upper and lower levels. We detected reversal of 21 OFs in their craniocaudal course. In conclusion, the radiological anatomy of the right OF differs from the left OF. The uppermost extent of the left OF is almost always higher than the right. Thus, higher position of the right OF compared with the left almost always indicates a pathological process. Assessment of the angles of the OFs or comparison of the two sides cannot be used for the diagnosis of parenchymal disease like atelectasis. Occasionally, the classical propeller-like configuration is disrupted by the reverse course of the caudal part of the OF.