What is the difference between bronchiolitis and bronchitis?

Bronchiolitis vs. Bronchitis: Key Differences and Diagnostic Approach

Bronchiolitis and bronchitis are distinct respiratory conditions affecting different parts of the airways, with bronchiolitis primarily affecting the small airways (bronchioles) and bronchitis affecting the larger bronchial tubes.

Bronchiolitis

Definition and Pathophysiology

• Bronchiolitis is a disorder most commonly caused by viral lower respiratory tract infection in infants, characterized by acute inflammation, edema, and necrosis of epithelial cells lining small airways, increased mucus production, and bronchospasm 1
• It involves inflammation, fibrosis, and architectural distortion of the small airways (bronchioles), which are less than 2 mm in diameter and do not contain cartilage or mucous glands 1, 2

Epidemiology and Etiology

• Most common in infants under 2 years of age, with respiratory syncytial virus (RSV) being the predominant cause in 90% of cases 1
• Other viral causes include human metapneumovirus, influenza, adenovirus, and parainfluenza 1
• In adults, bronchiolitis is uncommon and can result from various etiologies including infections, toxic exposures, or autoimmune conditions 1, 2

Clinical Presentation

• In infants: rhinitis, tachypnea, wheezing, cough, crackles, use of accessory muscles, and/or nasal flaring 1
• Typically begins with viral upper respiratory prodrome followed by increased respiratory distress 1
• In adults: cough and incompletely or nonreversible airflow limitation 1

Diagnosis

• In children: primarily a clinical diagnosis based on history and physical examination; laboratory and radiologic studies are not routinely recommended 1
• In adults: requires comprehensive medical history, physical examination, physiologic testing (spirometry with and without bronchodilator, lung volumes, and gas exchange), and radiographic studies 1
• High-resolution CT (HRCT) may show direct signs of abnormal bronchioles including dilation or airway wall thickening, nodular branching, and "tree-in-bud" abnormalities 1
• Chest radiographs are often normal in bronchiolitis due to the anatomic location of disease 1

Management

• For infants: primarily supportive care including adequate oxygenation and hydration 1
• Bronchodilators, corticosteroids, and antibiotics are not routinely recommended for bronchiolitis in children 1, 3
• For adults: treatment should be tailored to the specific cause or diagnosis 1
• For infectious bacterial bronchiolitis, prolonged antibiotic therapy is recommended 1

Bronchitis

Definition and Pathophysiology

• Bronchitis is inflammation of the larger airways (bronchi) in the lungs
• Acute bronchitis typically involves transient inflammation of the bronchi and bronchioles, usually caused by viral infections
• Chronic bronchitis is defined as productive cough lasting at least three months in two consecutive years

Clinical Presentation

• Productive cough with sputum production
• May include wheezing, chest discomfort, and shortness of breath
• In chronic bronchitis, symptoms persist over extended periods

Diagnosis

• Clinical diagnosis based on symptoms
• Chest X-ray may be normal or show increased bronchovascular markings
• Pulmonary function tests may show airflow obstruction in chronic cases

Management

• Acute bronchitis: typically self-limiting, supportive care
• Chronic bronchitis: bronchodilators, possibly inhaled corticosteroids, smoking cessation

Key Differences

1. Anatomical Location:

   • Bronchiolitis: Affects the small airways (bronchioles) that are less than 2mm in diameter 1, 2
   • Bronchitis: Affects the larger airways (bronchi)

2. Age Group:

   • Bronchiolitis: Predominantly affects infants and young children under 2 years 1
   • Bronchitis: Can affect all age groups, with chronic bronchitis more common in adults

3. Diagnostic Approach:

   • Bronchiolitis in children: Clinical diagnosis without routine need for imaging or laboratory tests 1
   • Bronchiolitis in adults: Often requires more extensive testing including HRCT and possibly lung biopsy 1
   • Bronchitis: Primarily clinical diagnosis based on symptoms

4. Treatment:

   • Bronchiolitis in children: Mainly supportive care; bronchodilators and corticosteroids not routinely recommended 1, 3
   • Bronchiolitis in adults: Treatment tailored to specific etiology 1
   • Bronchitis: Supportive care for acute cases; bronchodilators and possibly inhaled corticosteroids for chronic cases

Clinical Implications

• Accurate differentiation between bronchiolitis and bronchitis is crucial for appropriate management 4
• In children with bronchiolitis, avoid unnecessary interventions like routine use of bronchodilators, corticosteroids, or antibiotics 1
• In adults with suspected bronchiolitis, a thorough diagnostic workup is warranted to identify the specific etiology 1
• For both conditions, supportive care remains a cornerstone of management 1, 5

Pitfalls to Avoid

• Don't rely solely on chest X-rays for diagnosing bronchiolitis, as they are often normal despite significant disease 1
• Avoid overuse of antibiotics in viral bronchiolitis 1, 6
• Don't miss underlying risk factors for severe bronchiolitis in children, such as age less than 12 weeks, history of prematurity, underlying cardiopulmonary disease, or immunodeficiency 1
• For adults with suspected bronchiolitis, don't exclude the diagnosis based on normal HRCT findings alone, as clinically significant disease may be present despite absence of direct radiographic findings 1