American Board of Internal Medicine (ABIM) Certification Practice Exam

What imaging findings are characteristic of idiopathic pulmonary fibrosis (IPF)?

1. Ground-glass opacities and nodular infiltrates

2. High-resolution CT findings of basal-predominant septal line thickening and honeycomb changes

3. Consolidation and pleural effusion

4. Normal lung architecture on X-ray

The correct answer is: High-resolution CT findings of basal-predominant septal line thickening and honeycomb changes

Idiopathic pulmonary fibrosis (IPF) is characterized by specific imaging findings, particularly on high-resolution computed tomography (HRCT). The hallmark features on HRCT in patients with IPF include basal-predominant reticular opacities, which represent septal line thickening, and the presence of honeycombing. These findings are indicative of the fibrosis occurring in the lung interstitium. The basal predominance means that the lower lobes of the lungs are typically more affected than the upper lobes, a notable aspect when differentiating IPF from other interstitial lung diseases. Honeycombing appears as clustered cystic spaces and reflects advanced fibrotic changes, signifying severe lung remodeling. While other imaging findings such as ground-glass opacities can be seen in a variety of lung conditions, the combination of basal-predominant septal line thickening and honeycomb changes is a definitive signature of IPF. Options reflecting consolidation, pleural effusion, or normal lung architecture do not align with the characteristic findings of IPF, as these features are more typical of other types of lung pathology or represent different pulmonary conditions altogether.