• Aspiration of oily substances, such as mineral oil, oil based nose drops or Vicks VapoRub
  
• History of lipid use may be difficult to illicit from patient
  
• Radiographically, may be incidental finding of single or multiple irregular areas of consolidation in dependent lung
  
• Diagnosis can be made with CT if can demonstrate fatty tissue attenuation.
  
• Lipid laden macrophages may be seen in BAL fluid
  
• Patient usually asymtomatic but may have chronic cough
  
• Transthoracic needle biopsy can provide definitive diagnosis
  

General Imaging findings

Early

• Airspace opacification, confluent or discrete with air bronchograms
  
• May be large areas with stellate or well-defined margins
  
• In dependent lung, often segmental and in lower lobes
  
• In debilitated patients – in posterior segments of upper lobes and superior segments of lower lobes
  

Chronic

• Multifocal basal mass-like areas of consolidation with irregular margins
  
• Cicatricial volume loss in affected areas
  
• Interstitial pattern
  
• Well-circumscribed peripheral mass
  
• Gravity dependent lung segments
  

CT/HRCT

• Diagnosis made with CT when the opacities show fatty attenuation, –50 to –150 HU
  
• Lesions may have some ossification
  
• Lipoid etiology not apparent when interstitial pattern predominates
  
• Mixed ground glass and interlobular septal thickening may simulate alveolar proteinosis
  
• Fat may shift to dependent lung with postural change

MR findings

• MR may show fat - high T1 and T2 signal or chemical shift

• Hamartoma
  
• Inflammatory pseudotumor
  
• Bronchiolitis obliterans organizing pneumonia (BOOP)
  
• Bronchogenic carcinoma
  
• Alveolar proteinosis
• Differentiation
• Hamartoma may have fatty attenuation with CT. Usually solitary mass, < 4 cm and may have popcorn calcification
• Inflammatory pseudotumor, BOOP, bronchogenic carcinoma and alveolar proteinosis show no fatty attenuation at CT
  

• Mineral oil is most common agent, but may occur with animal or vegetable oils.
  
• Initial reaction is a bronchopneumonia. Macrophages ingest the lipid
  
• Clearing occurs by mucociliary transport or macrophage migration via the interstitium and lymphatics to mediastinal lymph nodes.
  
• Giant cell or granuloma formation may occur.
  
• With mineral oil aspiration, there are oil droplets within multinucleated giant cells, lymphocytes and fibrous tissue
  
• Chronically, lipid is fibrogenic
  

• Aspiration of oil used as a lubricant in infants with feeding problems
  
• Aspiration of mineral oil used for constipation in elderly
  
• Neurological or esophageal disease may promote aspiration
  
• Oil not irritant, aspiration often “silent”
  
• Most patients are asymptomatic and do not offer history of lipid use
  
• Commonly discovered as an incidental radiographic abnormality
  
• May have acute pneumonia with large amount of aspirated material
  
• Chronic cough
  
• Diagnosis by recovering lipid laden macrophages in BAL fluid or transthoracic needle biopsy
  
• Radiographic findings may disappear with discontinuation of use of lipoid agent
  
• Small amount aspirated – little impairment
  
• Large amounts – may develop restrictive lung disease or cor pulmonale
  
• May increase risk for bronchogenic carcinoma and nontuberculous mycobacterial infection

Seo JB, Im JG, Kim WS, et al. Shark liver oil-induced lipoid pneumonia in pigs: correlation of thin-section CT and histopathologic findings Radiology 212:88-96, 1999
Van den Plas O, Trigaux JP, Van Beers B, et al. Gravity-dependent infiltrates in a patient with lipoid pneumonia Chest 98:1253-1254, 1990
Wheeler PS, Stitik FP, Hutchins GM, et al. Diagnosis of lipoid pneumonia by computed tomography Jama 245:65-66, 1981