Peripheral Distribution (Reverse Bat-Wing)



Peripheral Distribution (Reverse Bat-Wing)


Robert B. Carr, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Contusion


Less Common



  • Eosinophilic Lung Disease


  • Cryptogenic Organizing Pneumonia


  • Pulmonary Infarct


  • Acute Respiratory Distress Syndrome


  • Radiation Pneumonitis


Rare but Important



  • Collagen Vascular Disease


  • Fat Embolism Syndrome


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Spares perihilar regions


  • Initially described on chest radiography


  • CT is more sensitive for detection of peripheral consolidation


  • Clinical history is essential


Helpful Clues for Common Diagnoses



  • Contusion



    • Interstitial and alveolar hemorrhage due to blunt thoracic injury


    • Occurs adjacent to site of chest wall trauma


    • Contrecoup contusions can occur, but rare


    • Not confined by fissural or segmental anatomic boundaries


    • Usually resolves within a few days


    • Persistence of opacities beyond a few days suggests alternate diagnosis, such as superimposed infection or aspiration


Helpful Clues for Less Common Diagnoses



  • Eosinophilic Lung Disease



    • Accumulation of eosinophils within distal airways and interstitium


    • Several forms of disease exist


    • Loeffler syndrome is most common form


    • Peripheral opacities are typical findings with these forms



      • Loeffler syndrome: Idiopathic peripheral consolidation that clears within 1 month (fleeting); also known as simple eosinophilic pneumonia


      • Chronic eosinophilic pneumonia: Peripheral consolidation associated with severe respiratory symptoms lasting at least 3 months, often with upper lobe predominance


      • Churg-Strauss syndrome: Middle-aged patient with allergies; lung disease resembles simple or chronic eosinophilic lung disease


    • Peripheral opacities are less commonly associated with these forms



      • Acute eosinophilic pneumonia: Acute respiratory failure with rapid response to steroids; appearance resembles more typical pulmonary edema


      • Hypereosinophilic syndrome: Multiorgan infiltration of eosinophils; usually presents with bilateral pulmonary nodules


  • Cryptogenic Organizing Pneumonia



    • Formerly known as idiopathic bronchiolitis obliterans organizing pneumonia (BOOP)


    • Accumulation of foamy macrophages and fibrosis in distal airways


    • Restrictive lung disease with chronic cough, shortness of breath, low-grade fever


    • Patchy areas of airspace consolidation or ground-glass opacities


    • Airspace disease is often in peripheral distribution


    • Tends to be peribronchovascular; can be unilateral or bilateral


    • More common in lower lungs


    • Other CT findings include



      • Peribronchial and centrilobular nodules


      • Atoll or reverse halo sign: Crescentic opacity with central ground-glass opacity


  • Pulmonary Infarct



    • Usually due to pulmonary artery emboli


    • Also associated with central bronchogenic carcinoma


    • More common in patients with poor cardiopulmonary reserve, impaired bronchial circulation


    • Subpleural pulmonary parenchymal consolidation, often wedge-shaped


    • Hampton hump: Wedge-shaped peripheral opacity with medial border oriented toward hilum



    • Central “bubbly” lucencies within peripheral consolidation is suggestive of diagnosis


  • Acute Respiratory Distress Syndrome



    • Damage to capillaries allows for loss of fluid into lung interstitium and alveolar spaces


    • Numerous causes: Trauma, infection, toxin exposure, emboli, DIC, drugs, pancreatitis, etc.


    • Idiopathic ARDS is known as acute interstitial pneumonia (AIP)


    • Often follows predictable time course



      • 1st 12-24 hours: Normal radiographic appearance


      • Several days: Bilateral scattered areas of consolidation; begins peripherally and then becomes confluent


      • Weeks: Slow resolution of lung consolidation


      • Months: May progress to lung fibrosis, often with anterior predominance


  • Radiation Pneumonitis



    • Occurs 1-3 months after radiation therapy


    • Occurs in approximately 40% of patients


    • Associated with diffuse alveolar damage within irradiated tissue


    • Ground-glass opacity &/or consolidation within lung tissue corresponding to location of radiation port


    • Does not respect fissural and segmental boundaries


    • Often asymptomatic


    • May resolve or progress to radiation fibrosis


    • Persistence > 9 months post radiation suggests presence of radiation fibrosis


Helpful Clues for Rare Diagnoses

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Aug 8, 2016 | Posted by in CARDIOLOGY | Comments Off on Peripheral Distribution (Reverse Bat-Wing)

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