Radiological and Clinical Findings in Acute and Chronic Exogenous Lipoid Pneumonia

Purpose: To describe the radiologic and clinical findings in a group of patients with exogenous lipoid pneumonia focusing on features that differentiate the acute and chronic presentations. Materials and Methods: We retrospectively identified 15 patients from a single institution with exogenous lipoid pneumonia 1992-2001. Inclusion criteria were: imaging with chest CT and either CT features diagnostic of lipoid pneumonia or intrapulmonary lipids on pathologic examination. Each chart was reviewed for the clinical presentation, history of ingestion/exposure, predisposing factors, treatment and response to therapy. Initial (n = 13) and follow-up (n = 11) chest radiographs were reviewed for the patterns and distribution of lung parenchymal abnormalities and pleural effusion. Initial (n = 15) and follow-up (n = 7) CT scans were reviewed for lung parenchymal abnormalities (consolidation, ground glass opacities, linear/nodular opacities, masses, and crazy paving), presence or absence of fat attenuation, and pleural effusion. The groups were compared using the Fischer exact test. Results: Nine patients had acute lipoid pneumonia, 7 males and 2 females with a mean age of 45 (range 4.5-81) years. Six patients had chronic lipoid pneumonia, 4 men and 2 women with a mean age of 63 (range 37-83) years. 78% (7/9) of patients with acute and all of the patients with chronic presentations had a known ingestion and/or a predisposing condition associated with lipoid pneumonia. On chest radiographs, consolidation and lower lobe involvement were present in the majority of patients with acute and none of the patients with chronic presentations. On CT, consolidation and fat attenuation were present in the majority of patients with each presentation. However, masses were present in 67% (4/6) of patients with chronic and none of the patients with acute presentation (P < 0.05). 86% (6/7) of patients with acute presentation had improvement on follow-up chest radiograph in contrast to none of the patients with chronic presentation (P < 0.05). 75% (3/4) of patients with acute lipoid pneumonia had improvement on follow-up CT in contrast with 67% (2/3) of patients with chronic lipoid pneumonia who had progression on follow-up CT. Conclusions: The imaging features of acute and chronic lipoid pneumonia overlap with consolidation and lower lobe involvement present in both groups. However, only the patients with acute lipoid pneumonia had pleural effusions and improvement on follow-up. Only the patients with chronic lipoid pneumonia had pulmonary masses.