Imaging in idiopathic pulmonary fibrosis: diagnosis and mimics

Abstract

Idiopathic pulmonary fibrosis is a chronic disease of unknown etiology that usually has a progressive course and is commonly associated with a poor prognosis. The main symptoms of idiopathic pulmonary fibrosis, including progressive dyspnea and dry cough, are often nonspecific. Chest high-resolution computed tomography is the primary modality used in the initial assessment of patients with suspected idiopathic pulmonary fibrosis and may have considerable influence on subsequent management decisions. The main role of computed tomography is to distinguish chronic fibrosing lung diseases with a usual interstitial pneumonia pattern from those presenting with a non-usual interstitial pneumonia pattern, suggesting an alternative diagnosis when possible. A usual interstitial pneumonia pattern on chest tomography is characterized by the presence subpleural and basal predominance, reticular abnormality honeycombing with or without traction bronchiectasis, and the absence of features suggestive of an alternative diagnosis. Idiopathic pulmonary fibrosis can be diagnosed according to clinical and radiological criteria in approximately 66.6% of cases. Confirmation of an idiopathic pulmonary fibrosis diagnosis is challenging, requiring the exclusion of pulmonary fibroses with known causes, such as asbestosis, connective tissue diseases, drug exposure, chronic hypersensitivity pneumonitis, and other forms of idiopathic interstitial pneumonitis. The histopathological hallmark of usual interstitial pneumonia is a heterogeneous appearance, characterized by areas of fibrosis with scarring and honeycombing alternating with areas of less affected or normal parenchyma. The aim of this article was to review the clinical, radiological, and pathological features of idiopathic pulmonary fibrosis and of diseases that might mimic idiopathic pulmonary fibrosis presentation.

Figure 1

Common features on high-resolution computed tomography in interstitial lung diseases. (a) Images from a 63-year-old female presenting a nonspecific interstitial pneumonia pattern. There are predominant areas of ground-glass opacities, with some traction bronchiectasis and cortical interlobular septal thickening. (b) Images from a 61-year-old male with idiopathic pulmonary fibrosis. There are diffuse areas of interlobular septal thickening, predominantly in the cortical lung zones. (c) Images from a 56-year-old female with idiopathic pulmonary fibrosis. There are extensive areas of honeycombing, with some interlobular septal thickening.

Figure 2

Images from a 53-year-old male with idiopathic pulmonary fibrosis. (a) Axial and (b) coronal computed tomography images demonstrating areas of honeycombing, reticulation and subpleural predominance. (c) Histopathology images demonstrating areas of marked fibrosis, with architectural distortion and fibroblast foci, alternating with areas of normal parenchyma.