Acute Pulmonary Consolidation

Jonathan H. Chung, MD

DIFFERENTIAL DIAGNOSIS

Common

Pneumonia
Cardiogenic Pulmonary Edema
Atelectasis
Aspiration
Pulmonary Contusion
Pulmonary Hemorrhage

Less Common

Hypersensitivity Pneumonitis (Acute)
Diffuse Alveolar Damage
Pulmonary Infarct

Rare but Important

Acute Eosinophilic Pneumonia
“Crack Lung”

ESSENTIAL INFORMATION

Helpful Clues for Common Diagnoses

Pneumonia
- Airspace opacities: Ground-glass to dense consolidation
- Reactive lymphadenopathy; very large lymph nodes unusual
- Parapneumonic pleural effusion or empyema
- Correlation with sputum, WBC count, and clinical presentation paramount
Cardiogenic Pulmonary Edema
- Due to imbalances in Starling forces: Usually due to increased pulmonary venous pressure
  - Left-sided heart failure (myocardial infarct or ischemic cardiomyopathy)
  - Fluid overload or renal failure
  - Mitral valve disease
- Interlobular septal thickening: Kerley-B and Kerley-A lines on chest radiograph
- Diffuse, hazy airspace opacities
  - Characteristically central-predominant due to higher concentration of lymphatics in peripheral aspect of lungs
- Cardiomegaly frequently noted
- Signs of coronary artery disease (coronary artery calcification, CABG, coronary artery stents, subendocardial fatty metaplasia)
Atelectasis
- Subsegmental
  - Discoid or linear opacity most often in mid and lower lungs
  - Hypoventilation or decreased diaphragmatic excursion (splinting, neuromuscular abnormality, subdiaphragmatic mass effect)
  - Small airways disease (secretions leading to resorptive atelectasis, asthma, viral bronchiolitis)
  - Decreased surfactant production (pulmonary embolism)
  - Compression (mass effect from adjacent pathology)
- Lobar
  - Lobar volume loss: Displacement of pulmonary fissures, ipsilateral shift of mediastinum and hilum toward affected lobe, superior shift of diaphragm
  - Increased opacity of affected lobe
  - Combined right middle and lower lobe atelectasis from bronchus intermedius obstruction; mimics pleural effusion
  - In acute setting, most often due to obstruction of bronchus due to mucous plugging or foreign body
Aspiration
- Consolidation in gravity-dependent portions of lungs
- Predisposed patients (e.g., those with alcoholism, epilepsy, hiatal hernia, esophageal dysmotility or obstruction, neuromuscular disorders)
- Supine: Superior segments of lower lobes and posterior segments of upper lobes
- Upright: Basilar segments of lower lobes
- Centrilobular or tree in bud opacities common on CT
- Can progress to necrotizing pneumonia or pulmonary abscess without treatment
Pulmonary Contusion
- Acute blunt trauma; appears at time of injury and resolves in 3-5 days
- Peripheral, under point of blunt kinetic energy absorption
  - Often lateral portions of lung away from overlying musculature
  - Overlying rib fractures; but can occur without rib fractures in children and young adults
Pulmonary Hemorrhage
- Widespread
  - Vasculitis, anticoagulation, idiopathic pulmonary hemosiderosis
- Focal
  - Mass, aspiration, bronchiectasis, trauma
- Ground-glass opacities > consolidation; may be diffuse, patchy, lobular, or centrilobular
- Tendency to spare peripheral, apical, and costophrenic aspects of lungs
- Increased interlobular and intralobular septal thickening over 1-2 days
- Rapid resolution in days, though not as rapid as in cardiogenic pulmonary edema or bland aspiration
- In recurrent hemorrhage, may result in lung fibrosis

Helpful Clues for Less Common Diagnoses

Hypersensitivity Pneumonitis (Acute)
- Allergic reaction to airborne organic particles
- Diffuse or centrilobular ground-glass opacities; lobular air-trapping
Diffuse Alveolar Damage
- Noncardiogenic pulmonary edema
- Clinical correlate is acute respiratory distress syndrome
- Heterogeneous, diffuse ground-glass opacities and consolidation
- Often with anterior-posterior and superior-inferior gradient
- Large pleural effusions and severe interlobular septal thickening uncommon
- Varicoid bronchiectasis, reticular opacities, and honeycombing common 2-3 weeks after onset of respiratory distress
Pulmonary Infarct
- Most often from pulmonary arterial embolism
- Often in setting of superimposed cardiac dysfunction (cardiomyopathy, congestive heart failure)
- Lower lung predominant, peripheral/subpleural, wedge-shaped consolidation: Hampton hump sign
- Resolves over months; retains its original shape rather than patchy resolution as in pneumonia

Helpful Clues for Rare Diagnoses

Acute Eosinophilic Pneumonia
- Probable hypersensitivity reaction to inhaled agents; possible association with smoking
- Imaging mimics pulmonary edema
  - Ground-glass opacities > consolidation
  - Interlobular septal thickening
  - Pleural effusions
- Acute high fever, profound dyspnea, myalgia, pleuritic chest pain
- Responds rapidly to steroids
“Crack Lung”
- “Crack” = smoked form of cocaine
- Hypersensitivity reaction, pulmonary hemorrhage, pulmonary edema (cardiogenic and noncardiogenic)
- Noncardiogenic pulmonary edema may be peripheral and bilateral as opposed to cardiogenic edema
- Pneumomediastinum or pneumothorax