Exogenous lipoid pneumonia: when radiologist makes the difference

Abstract

Purpose: To report high-resolution CT (HRCT) findings in our group of patients with exogenous lipoid pneumonia (ELP), confirmed with histopathological findings and clinical-anamnestic data, in order to describe the most common radiological patterns of this rare disorder.

Materials and methods: In this retrospective study, HRCT of 10 patients with ELP were evaluated by three radiologists. Diagnosis of ELP was made through CT, bronchiolo-alveolar lavage (BAL) and a pneumological examination associated with an accurate medical anamnesis. Five patients had a histologically proven ELP, through lung biopsy. All patients had a chronic exposition to substances made of animal fat or mineral/vegetable oils.

Results: In our cohort of patients with ELP, the following parenchymal patterns were observed: 8/10 patients had lung consolidation with adipose density (attenuation values < - 40 HU); 10/10 patients had multiple areas of ground glass opacity; 6/10 patients had smooth thickening of interlobular septa and ground glass opacities ("crazy-paving" pattern); 2/10 patients presented nodules > 2.5 cm with spiculated margins (tumor-like); 5/10 patients showed reactive lymph nodes enlargement. The oldest lesions were characterized by bronchiectasis and fibrosis around the lipidic consolidations.

Conclusion: Pulmonary alterations found in HRCT exams can be confused with other lung diseases (especially lung tumors) and they are always a challenge even for the most experienced radiologist. In our experience, although non-specific, consolidation areas with low HU values and crazy-paving pattern are frequently associated in ELP. These characteristics should alert the radiologist to consider ELP among the possible differential diagnoses, always correlating the results of CT examination with appropriate clinical-laboratory evaluations and an accurate anamnesis.

Keywords: Computed tomography; HRCT; Lung; Pneumonia.