Wheezing

Jud W. Gurney, MD, FACR

DIFFERENTIAL DIAGNOSIS

Common

Asthma
Cardiogenic Pulmonary Edema
Pulmonary Emboli
Aspiration

Less Common

Airway Obstruction
- Extrinsic: Airway Compression
- Intrinsic: Airway Narrowing
Allergic Bronchopulmonary Aspergillosis
Tracheobronchomalacia
Churg-Strauss Syndrome
Eosinophilic Pneumonia

Rare but Important

Carcinoid
Diffuse Neuroendocrine Hyperplasia
Mastocytosis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Wheezing: High-pitched adventitious sound superimposed on normal sounds of breathing; occurs when air flows rapidly through narrowed bronchi

Helpful Clues for Common Diagnoses

Asthma
- “All that wheezes is not asthma”
- Primarily involves small to medium-sized bronchi
- Bronchial wall (BW) thickened by edema, ↑ smooth muscle, ↑ size mucus glands
- HRCT: BW thickening in 50-90%
- Near-fatal asthma: Centrilobular nodules ↑, (seen in 100%) but not specific (seen in up to 1/3 of mild asthma)
- Air-trapping (total volume > 1 segment) in 50%
- Complications of asthmatic attacks
  - Pneumomediastinum (5%)
  - Pneumonia (2%)
  - Pneumothorax (0.3%)
  - Lobar atelectasis from mucus plugs (rare)
Cardiogenic Pulmonary Edema
- Interstitial edema thickens bronchial walls, narrowing their lumen
- Associated findings: Cardiomegaly, pleural effusions, interstitial septal thickening
Pulmonary Emboli
- Acute emboli associated with reflex bronchoconstriction of embolized segment, leads to wheezing
- Recurrent emboli may give rise to episodic wheezing and misdiagnosis of asthma
- 10% of patients with acute pulmonary emboli have wheezing as predominant symptom
Aspiration
- Repeated episodes of aspiration may give rise to wheezing as aspirated material narrows airway lumen
- Aspiration most common in dependent segments
  - Posterior segments of upper lobes and superior segments of lower lobes in recumbent position
  - Lower lobe basilar segments in upright position

Helpful Clues for Less Common Diagnoses

Airway Obstruction
- Extrinsic: Airway Compression
  - Most commonly goiters, vascular rings
- Intrinsic: Airway Narrowing
  - Most commonly from neoplastic and nonneoplastic tumors, tuberculosis, or foreign bodies
- Even with fixed obstruction, patient may have intermittent wheezing and be misdiagnosed with asthma for mths or yrs
Allergic Bronchopulmonary Aspergillosis
- Hypersensitivity reaction to Aspergillus fumigatus
- Occurs in 1-2% of chronic asthmatics
- HRCT: Central bronchiectasis with peripheral sparing, primarily involves upper lung zones
Tracheobronchomalacia
- Softening of airway cartilage
- Excessive collapse (> 70%) of expected luminal area during expiratory CT scan
- Typical morphology: Crescent, lunate, or “frown” sign
Churg-Strauss Syndrome
- Granulomatous small vessel vasculitis
- Most present with peripheral neuropathy (mononeuritis multiplex)
- Nearly 100% have asthma
- Triad of allergic history, peripheral blood eosinophilia, and systemic vasculitis
- CT: Nonspecific but similar to chronic eosinophilic pneumonia with peripheral consolidation and ground-glass opacities
- Pleural effusions in 25% (extremely rare in eosinophilic pneumonia)
Eosinophilic Pneumonia
- Asthma seen in 50% of chronic eosinophilic pneumonia
- Striking peripheral consolidation, primarily of upper lung zones

Helpful Clues for Rare Diagnoses

Carcinoid
- Carcinoid syndrome: Wheezing from excess serotonin and histamine
- Carcinoid syndrome uncommon with pulmonary carcinoids, seen in 2-5% of patients, almost all of whom have hepatic metastases
- Endobronchial component of carcinoid tumors may give rise to unilateral wheezing
- Hemoptysis also common as tumors are vascular
Diffuse Neuroendocrine Hyperplasia
- Rare disorder of proliferation of carcinoid tumorlets (benign)
- Primarily women; may also be more common in those living at high altitude
- Multiple pulmonary nodules (< 5 mm diameter) + mosaic attenuation
- Mosaicism may be related to endobronchial tumorlets or associated constrictive (obliterative) bronchiolitis
- 1/3 have asthma
Mastocytosis
- Rare disorder with proliferation of mast cells in extracutaneous organs
- Lung involvement shows centrilobular nodules and cysts (or emphysema)
- Skeletal: Diffuse osteosclerosis from bone marrow infiltration
- GI tract and spleen more often involved than lung
- Asthma due to excess histamine

Other Essential Information

Acute onset wheezing
- Asthma
- Congestive heart failure
- Pneumonia
- Pulmonary embolus
- Aspiration syndromes
- Foreign body
Insidious onset wheezing
- Endobronchial tumor
- Congestive heart failure
- Extrinsic airway narrowing
Course of symptoms
- Intermittent: Asthma, aspiration, pulmonary embolus, congestive heart failure, foreign bodies
- Persistent: Asthma, extrinsic or intrinsic airway narrowing, Churg-Strauss vasculitis
- Progressive: Asthma, tumors, eosinophilic pneumonia, Churg-Strauss vasculitis

Image Gallery

Frontal radiograph shows marked hyperinflation. Note the asthma inhaler

left in shirt pocket. Radiographs have limited utility in asthma, as they may be normal even in patients with status asthmaticus.

Lateral radiograph shows flattened hemidiaphragms and increased retrosternal lucency. Asthma complications include pneumomediastinum, pneumothorax, atelectasis from mucus plugging, and pneumonia.

(Left) Axial HRCT shows bronchial wall thickening

; other airways are normal. Note that study was CTA for suspected pulmonary embolus. Some airways may be mildly dilated and may reflect bronchodilatation from uninvolved airways. (Right) Axial HRCT shows bronchial wall thickening