A 35-year-old man with known COPD presents with acute dyspnea. CT chest is performed and confirms pneumothorax. Which of the following statements regarding imaging findings in secondary pneumothorax is NOT true?

## Secondary Pneumothorax: Imaging Characteristics **Key Point:** Secondary pneumothorax occurs in patients with underlying lung disease (COPD, IPF, cystic fibrosis, sarcoidosis, PCP pneumonia). The imaging shows both the pneumothorax AND evidence of the underlying pathology. ### Distinguishing Secondary from Primary Pneumothorax | Feature | Primary PTX | Secondary PTX | |---------|------------|---------------| | **Underlying lung disease** | None (or minimal) | Always present (COPD, IPF, CF, etc.) | | **Age** | Young (15–35 years) | Usually older (>40 years) | | **Recurrence rate** | ~25% | ~40–50% | | **Bullae/blebs** | May be present but not required | Often visible; source of rupture | | **Associated findings** | Minimal parenchymal change | Emphysema, bronchiectasis, fibrosis evident | | **Location** | Apical/anterior (simple) | Variable; may be diffuse | **High-Yield:** Secondary PTX is NOT always apical or loculated. In fact, secondary PTX can be **diffuse, loculated, or multiloculated** depending on the underlying lung disease and degree of pleural adhesions. A pneumothorax in a patient with COPD may be basal, lateral, or diffuse — not confined to the apex. ### CT Findings in Secondary Pneumothorax 1. **Bullae and blebs** — Rupture source; typically at lung apex in COPD but can be anywhere 2. **Emphysematous changes** — Hypodense lung parenchyma, loss of normal architecture 3. **Bronchial wall thickening** — Sign of chronic airway disease 4. **Fibrosis or bronchiectasis** — If IPF or CF is the underlying cause 5. **Pleural adhesions** — May loculate the air collection, but NOT always **Clinical Pearl:** A patient with COPD and pneumothorax may have a **basilar or diffuse pneumothorax**, not confined to the apex. The presence of pleural adhesions (from prior inflammation, infection, or surgery) can create loculated air pockets anywhere in the pleural space. ### Why Loculation is NOT Always Present - **Primary PTX:** Simple, unloculated (air dissects freely in pleural space) - **Secondary PTX:** May be simple OR loculated depending on: - Degree of pleural adhesions - Extent of underlying inflammation - Prior pleural disease - Location of rupture site **Mnemonic:** **COPD-PTX** = Chronic Obstructive Pulmonary Disease–Pneumothorax. Think: "COPD patients can have PTX anywhere, not just the apex." **Tip:** On exam, if asked about secondary PTX imaging, remember that the pneumothorax location and morphology depend on the underlying disease and pleural adhesions — NOT a fixed rule of apical loculation.