Cough

Christopher M. Walker, MD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Over 1,000 conditions associated with cough
- Review focuses on selected causes of cough identified on thoracic imaging
Chronic cough defined by duration ≥ 3 weeks
- Commonly secondary to post-nasal drip, asthma, GERD, chronic bronchitis, bronchiectasis, ACE inhibitor medications, and extrinsic tracheal compression
- Most are radiographically occult

Helpful Clues for Common Diagnoses

Pneumonia
- Lobar or segmental lung consolidation
- ± pleural effusion
Chronic Bronchitis
- ± bronchial wall thickening &/or mucus plugging
Asthma
- ± hyperinflation
- ± bronchial wall thickening
- Complications include pneumonia, pneumothorax, pneumomediastinum, or atelectasis
Congestive Heart Failure
- Cardiomegaly and pleural effusions
- Kerley B lines
Malignancy
- Bronchogenic carcinoma
  - Spiculated lung nodule or mass
  - ± lymphadenopathy
- Lymphangitic carcinomatosis
  - Smooth or nodular thickening of interlobular septa
  - ± pleural effusions and lymphadenopathy

Helpful Clues for Less Common Diagnoses

Pulmonary Embolism
- CTA: Filling defect diagnostic
  - “Railroad track” or “doughnut” signs
- Document signs of right heart strain
  - RV/LV chamber size >1, leftward bowing of interventricular septum, or reflux of contrast into IVC
Pneumothorax
- Spontaneous
  - Young, tall, and thin male smokers
  - Also seen in emphysema, asthma, infection, lung fibrosis, or cystic lung disease
- Traumatic or iatrogenic
Mycobacterium Infection
- M. tuberculosis
  - Upper lobe cavitary nodule
  - Tree in bud opacities indicates endobronchial spread of disease
- M. avium complex
  - Older women
  - Middle lobe or lingular bronchiectasis
  - Tree in bud opacities
Cystic Fibrosis
- Hyperinflation with bronchiectasis
- Early upper lobe involvement
Sarcoidosis
- Paratracheal and symmetric hilar lymphadenopathy
- ± perilymphatic lung nodules (nodules along fissures, subpleural lung, and bronchovascular bundles)
Bronchiectasis
- Tram-tracking
- CT diagnostic
  - Bronchus ≥ in size than adjacent artery
Smoking-Related Interstitial Lung Disease
- Respiratory bronchiolitis associated interstitial lung disease
  - Symptomatic smoker
  - Upper lung predominant centrilobular nodules of ground-glass opacity
- Desquamative interstitial pneumonia
  - Diffuse/patchy, lower lung predominant ground-glass opacity
  - ± cystic spaces and centrilobular emphysema

Helpful Clues for Rare Diagnoses

Usual Interstitial Pneumonia
- Basal and subpleural fibrosis with honeycombing
- ± mediastinal lymphadenopathy
Hypersensitivity Pneumonitis
- Centrilobular nodules of ground-glass opacity
- “Head-cheese” sign
  - Ground-glass opacity, air-trapping, and normal lung
Pneumoconioses
- Asbestosis
  - Posterobasal and subpleural lung
  - Bilateral pleural plaques
  - Reticular and dot-like opacities early
  - Fibrosis and distortion late
- Silicosis/Coal worker’s pneumoconiosis
  - Posterior and superior lung
  - Centrilobular and subpleural nodules
  - ± calcified lymphadenopathy
Langerhans Cell Histiocytosis
- Smokers, 20-40 years old
- Centrilobular nodules and cavitary nodules
- Spares costophrenic sulci
- Round or bizarrely shaped cysts
- ± pneumothorax
Goodpasture Syndrome
- Hemoptysis
- Ground-glass opacity or consolidation
Bronchioloalveolar Cell Carcinoma
- Chronic ground-glass opacity with “pseudocavitation”
Constrictive Bronchiolitis
- Bronchiectasis, mosaic perfusion, and expiratory air-trapping
- Causes include
  - Infection, toxic fume inhalation, collagen vascular diseases, and chronic lung transplant rejection
Pulmonary Alveolar Proteinosis
- Chronic crazy-paving
  - Geographic ground-glass opacity with superimposed interlobular septal thickening
Foreign Body
- History key to diagnosis
Lipoid Pneumonia
- Aspiration of oils used for laxatives
- Lower lobe consolidation or mass
  - Central low attenuation areas (-80 to -30 HU)