Chronic Bronchitis: High-Yield Pathology
Chronic bronchitis is defined clinically by a persistent productive cough for at least 3 months in at least 2 consecutive years. It is a major form of COPD, primarily driven by chronic irritation (most commonly smoking).
1. Morphological Hallmarks
| Pathology | Description |
|---|---|
| Mucus Gland Hyperplasia | Hypertrophy and hyperplasia of mucus-secreting glands in the bronchi. |
| Reid Index | The ratio of the thickness of the mucous gland layer to the thickness of the wall between the epithelium and cartilage. In chronic bronchitis, this is increased (>0.4). |
| Goblet Cell Metaplasia | Increase in the number of goblet cells in small airways, contributing to excess mucus production. |
2. Exam Must-Knows
- Clinical Phenotype: Often called “Blue Bloaters.” Hypoxemia and hypercapnia are common due to significant ventilation-perfusion (
) mismatch.
- Complications: Chronic hypoxia leads to pulmonary hypertension, which can result in right-sided heart failure (cor pulmonale).
- Smoking Association: Smoking is the primary irritant that triggers the inflammatory response, leading to bronchial wall thickening and luminal obstruction.
3. Clinical Pearl
Diagnostic Distinction: While emphysema is characterized by alveolar wall destruction (leading to increased compliance), chronic bronchitis is defined by mucus gland hypertrophy (leading to airway obstruction). They often coexist in patients with smoking-related COPD.