Asthma (summary)

This is a basic article for medical students and other non-radiologists

Asthma is a heterogeneous disease, usually characterized by chronic airway inflammation and airway hyperreactivity. It is defined by two main features :

• a history of respiratory symptoms such as wheeze, shortness of breath, chest tightness and cough that vary over time and in intensity, AND
• variable expiratory airflow limitation

Reference article

This is a summary article; read more in our article on asthma.

Summary

• epidemiology
  • one of the most common chronic diseases worldwide
  • prevalence in the UK: 16%
  • symptoms usually begin before age 5
• presentation
  • classical symptoms
    • wheeze, shortness of breath, chest tightness or difficulty breathing and cough
  • episodic exacerbations may be triggered
    • exercise, allergens, irritants, cold air, viral infection
• pathology
  • three major features
    • bronchoconstriction: acute airway narrowing due to bronchial smooth muscle contraction
    • airway hyperresponsiveness: excessive bronchoconstrictor response to stimuli
    • airway inflammation: with edema and mucus hypersecretion
• investigation
  • FEV1
  • lung function tests
  • CXR in acute exacerbations if there is concern for infection
  • CT chest may be required in severe exacerbations
• treatment
  • treatment goals
    • symptoms control
    • exacerbation prevention
    • prevention of loss of lung function
    • reduce associated mortality
  • medical management
    • inhaled beta-agonist therapy
    • oral steroids in acute exacerbations
• prognosis
  • depends on the severity of disease and symptom control
  • patients may be symptom-free for long periods of time
  • acute exacerbations may be severe
  • death due to asthma is rare

Role of imaging

• assess for evidence of infection
• assess for complications, e.g. pneumothorax

Radiographic features

Plain radiograph

Chest x-rays at diagnosis should be reserved for children with severe disease or in any patient with atypical features or clinical symptoms or signs suggesting other conditions.

In acute asthma, a chest x-ray is only required if there is :

• suspected pneumomediastinum, pneumothorax or surgical emphysema
• suspected consolidation
• requirement for ventilation or life-threatening asthma
• failure to respond to treatment satisfactorily

The radiographic features of asthma are not specific. In the absence of other concurrent illness the chest radiograph is almost always normal in patients with asthma. Possible findings are bronchial wall thickening and hyperinflation (although marked hyperinflation is uncommon in patients who do not also have emphysema) .

CT

CT is only indicated to identify associated conditions, particularly allergic bronchopulmonary aspergillosis (ABPA), eosinophilic pneumonia and eosinophilic granulomatosis with polyangiitis (previously known as Churg Strauss syndrome), and mimics of asthma such as hypersensitivity pneumonitis.

In asthmatic patients, CT can show bronchial wall thickening with narrowing of the bronchial lumen and expiratory air trapping. Mild cylindric bronchiectasis and pulmonary cysts are also seen with increased frequency in patients with asthma .