Lung Abscess

  • Etiology: gram positive cocci predominate, consider gram negative bacilli + anaerobes in patient with aspiration
  • Imaging: spherical in shape, destroys lung, thick walled cavity with air fluid levels after necrotic pneumonia
  • US: moves with respiration which distinguishes it from empyema
  • DDX: pleural empyema
    — Abscess – spherical in shape, destroys lung
    — Empyema – nonspherical in shape, displaces lung, split pleura sign, enhancing rim sign of pleura, obtuse angles to chest wall, thickened pleura
  • DDX: pneumatocele
    — Abscess appears earlier in infection, has thick irregular walls, lasts long time
    — Pneumatocoele occurs later in infection, has thin wall, usually no air fluid level
  • DDX: infected congenital pulmonary airway malformation / bronchopulmonary foregut malformation which often present with recurrent lung infections
    — Repeat imaging after infection resolves to look for residual lesion

Cases of Lung Abscess

CXR of lung abscess
CXR shows a round cavitary lesion with an air-fluid level in the left upper lobe.
CXR and CT of lung abscess
CXR and axial and coronal CT without contrast of the chest shows a cavitary mass in the densely consolidated left lower lobe and a moderate left pleural effusion.