CTICasesBilateral Lower Lobe Atelectasis Mimicking Pleural Effusion on Supine Radiograph
Imaging findings
Portable supine chest radiographs demonstrate bilateral basilar opacities with a graduated density pattern that resembled pleural fluid accumulation. CT correlation reveals extensive bilateral lower lobe atelectasis; the pulmonary vessels visible through the opacity are from the right middle lobe and left upper lobe draped over collapsed lower lobes.
Key takeaways
On supine or semi-recumbent portable chest radiographs, bilateral lower lobe atelectasis can produce a graduated opacity that is indistinguishable from pleural fluid. The presence of pulmonary vessels visible through the opacity may paradoxically be misleading, as these may belong to overlying non-atelectatic lobes rather than the collapsed segment. CT is the definitive discriminator. When interpreting bedside radiographs, acknowledging diagnostic uncertainty about the relative contributions of atelectasis versus effusion is clinically appropriate.
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