On an axial CT chest at the level of the carina, the 'bat wing' or 'butterfly' pattern of bilateral perihilar ground-glass opacification sparing the periphery is characteristic of:
- A Acute pulmonary oedema (cardiogenic) ✓
- B Community-acquired pneumococcal pneumonia
- C Cryptogenic organising pneumonia (COP)
- D Pulmonary alveolar proteinosis
Correct answer: A. Acute pulmonary oedema (cardiogenic)
Explanation
Bilateral central (perihilar) ground-glass opacity sparing the peripheral 3–4 cm — the 'bat wing' or 'butterfly' distribution — is characteristic of acute cardiogenic pulmonary oedema. The mechanism relates to the preferential distribution of elevated pulmonary venous pressure centrally. COP shows peripheral consolidation (the reverse pattern). Lobar pneumonia is segmental. Pulmonary alveolar proteinosis shows a 'crazy paving' pattern (GGO with superimposed reticulation).
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.