113 Exogenous Lipoid Pneumonia

Clinical Presentation

41-year-old man with mental retardation. CT scan was acquired to evaluate a suspected lung mass identified on outside chest radiography (not available).

Radiologic Findings

Contrast-enhanced chest CT (Fig. 113.1A, mediastinal window; Fig. 113.1B, lung window) through the right middle lobe demonstrates a focal mass-like region of consolidation with a mild degree of surrounding ground glass. Note the low-attenuation regions in the consolidation. Contrast-enhanced chest CT (Fig. 113.1C, mediastinal window; Fig. 113.1D, lung window) through the lower lobes demonstrates mass-like regions of basilar consolidation containing low-attenuation areas and surrounding ground glass. Mild interlobular septal thickening is seen in the right base. A calcified nodule is present in the right lung base. Corresponding chest CT images with deposited regions of interest reveal attenuation coefficients ranging between –80 HU in the left lower lobe (Fig. 113.1E) and –44 HU in the right lower lobe (Fig. 113.1F). The attenuation coefficients in the right middle lobe consolidation were estimated at –68 HU (not illustrated).

Diagnosis

Exogenous Lipoid Pneumonia

Differential Diagnosis

• Endogenous Lipoid Pneumonia—in the setting of proximal or distal airway obstruction

• Pseudolipoid Pneumonia—an air bubble artifact associated with collapse of air spaces

• Infection

• Primary Lung Cancer

• Pulmonary Lymphoma

• Other Fat-Containing Lesions

Differential Diagnosis: Other Intrathoracic Fat-Containing Lesions

• Hamartoma

• Lipoma

• Liposarcoma

• Germ Cell Tumors

• Mediastinal Lipomatosis

• Thymolipoma

• Diaphragmatic Hernias, Fat Herniation

Discussion

Background

Exogenous lipid pneumonia (ELP) is an uncommon cause of parenchymal consolidation secondary to chronic aspiration or inhalation of animal, vegetable, or petroleum-based oils or fats.