Pulmonary parenchymal consolidation on thoracic CT: Clues to a specific diagnosis

Consolidation is defined pathologically as an exudate, or other disease product, that replaces alveolar air and renders the pulmonary parenchyma airless. The chest radiographic appearance of consolidation is usually relatively nonspecific and may be the result of a wide variety of disorders, including infection, neoplasm, hemorrhage, and rare infiltrative diseases. Similarly, the appearance of consolidation on thoracic computed tomography (CT) is rarely specific enough to suggest a single diagnosis. Occasionally, however, the attenuation characteristics of consolidation on thoracic CT may provide a specific etiology for pulmonary parenchymal infiltration; such is the case when low attenuation material, representing fat, is seen in patients with lipoid pneumonia on thoracic CT. Often the diagnosis of lipoid pneumonia is difficult to establish clinically, and abnormalities detected on thoracic CT may first suggest this condition. Once thoracic CT indicates the presence of lipoid pneumonia, directed history often discloses the offending agent. Bronchoscopy with bronchioloalveolar lavage may disclose lipid-laden macrophages within the lung parenchyma in selected patients. Therapy may then be directed at discontinuation of the offending lipid and treatment of any coexistent bacterial superinfection. Patients with acute lipoid pneumonia often improve clinically and radiographically with appropriate therapy, whereas patients with chronic lipoid pneumonia may show relatively little improvement despite appropriate treatment.