On an axial CT of the thorax at the level of the right hilar vessels, a thin line of soft tissue density extends from the hilum laterally and anteriorly to the chest wall, separating aerated lung above and below it. This represents which fissure?

• A Oblique fissure of the right lung
• B Superior accessory fissure
• C Oblique fissure of the left lung
• D Horizontal fissure of the right lung ✓

Explanation

The horizontal fissure runs from the right hilum forward to the anterior chest wall in the plane of the fourth rib, so on axial sections it appears as a thin line separating the right upper and middle lobes. The oblique fissures run posterosuperiorly to anteroinferiorly and therefore appear as broad bands cutting across successive axial slices rather than a single line reaching the sternum.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.