X-ray Findings of Pulmonary Emphysema vs Pulmonary Fibrosis
The key distinguishing radiological features of pulmonary emphysema versus pulmonary fibrosis are their distribution patterns and characteristic findings: emphysema presents as areas of decreased attenuation predominantly in upper lung zones, while fibrosis shows reticular opacities, traction bronchiectasis, and honeycombing predominantly in lower lung zones. 1
Pulmonary Emphysema: Radiological Features
- Emphysema appears as areas of decreased attenuation (abnormally dark areas) without visible walls, representing destruction of alveolar walls 1
- Predominantly affects upper lung zones, particularly in smokers 2
- Visual scoring of emphysema is used to determine whether it spans ≥15% of total lung volume, which is associated with increased risk of complications 1
- Characterized by reduced lung markings and hyperinflation with flattened diaphragms 2
- Bullae (air-filled spaces >1 cm in diameter) may be present, especially in severe cases 2
- Vascular markings are attenuated or absent in affected areas 2
Pulmonary Fibrosis: Radiological Features
- Fibrosis is confidently recognized when traction bronchiectasis/bronchiolectasis and/or honeycombing are identified 1
- Predominantly affects basal and subpleural regions of the lungs 1
- Key findings include:
- Honeycombing: clustered cystic airspaces with well-defined walls, representing end-stage fibrosis 1, 3
- Traction bronchiectasis: irregular bronchial dilatation caused by contractile forces from surrounding fibrotic tissue 3
- Reticular opacities: network of fine linear opacities representing fibrotic thickening of interlobular septa 1
- Ground-glass opacities: when associated with architectural distortion, suggest active inflammation or fine fibrosis 1
Distinguishing Features and Potential Pitfalls
- Honeycombing must be distinguished from paraseptal emphysema and airspace enlargement with fibrosis 1
- Traction bronchiectasis appears as dilated bronchi within areas of fibrotic lung tissue (signet ring sign) and is a key marker of irreversible fibrosis 3
- In fibrosis, the remodeling process appears as a continuum from traction bronchiectasis to honeycombing 1
- Emphysema is characterized by decreased attenuation without visible walls, while honeycombing shows cystic spaces with well-defined walls 1, 2
Combined Pulmonary Fibrosis and Emphysema (CPFE)
- CPFE is a distinct syndrome characterized by emphysema in upper lung zones and fibrosis in lower lung zones 4, 2
- Affects predominantly male smokers with severe dyspnea 5
- Presents with relatively preserved lung volumes on spirometry but severely impaired diffusion capacity 5
- Has high prevalence (36-39%) among patients with fibrotic interstitial lung disease 6
- Associated with increased risk of pulmonary hypertension and lung cancer 4, 5
- Has worse prognosis than either condition alone 2
Diagnostic Approach
- High-resolution CT (HRCT) is the diagnostic procedure of choice for both conditions 3
- Multi-planar reconstruction on sagittal and coronal planes should be evaluated to increase diagnostic confidence 1
- For fibrosis assessment, the extent is determined by visually estimating the percentage of parenchymal involvement 1
- For emphysema, visual scoring can identify not only the overall extent but also specific morphological features 1
- When both patterns coexist, a systematic multidisciplinary approach involving pulmonologists, radiologists, and pathologists is recommended 7
Clinical Implications
- The presence of traction bronchiectasis in a probable UIP pattern on HRCT increases the likelihood of IPF diagnosis 3
- Extent of emphysema >15% must be reported as it is associated with comorbidities and disease progression 1
- The UIP pattern is a hallmark of IPF but can also be seen in fibrotic hypersensitivity pneumonitis and connective tissue disease 1
- Identification of the correct pattern guides treatment decisions: antifibrotic therapy for fibrosis versus bronchodilators for emphysema 7