What causes Incomplete fissure sign in lungs on CT? Let me know in the comments.
Let me know in the comments.
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Answer:
Incomplete fissure sign refers to a pulmonary interlobar fissure that does not extend fully across the lung, resulting in a characteristic lobar opacity pattern or incomplete lobar collapse, most commonly due to loculated pleural effusion layering into the incomplete portion of the fissure.
Why is it called so?:
Named for the key radiographic feature of an interlobar fissure that is anatomically or functionally incomplete, failing to traverse the full extent of the lung parenchyma, which allows partial fluid accumulation and produces a distinct opacity bordering a perihilar lucency.
Pathophysiology:
Pleural fluid preferentially accumulates in the dependent portion of an incomplete major interlobar fissure due to its partial development, creating a curvilinear demarcation with perihilar lucency medially and lateral opacity; this explains the stair-step appearance in partial collapse or effusion, as the fissure acts as a partial barrier to complete lobe expansion or fluid distribution.
Alternative names: Incomplete pulmonary interlobar fissure sign
Other associated named signs: Middle lobe stair-step sign
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