Paper II
Question
(
- (a) Define pneumonia ( 1 mark(s)
- (b) Describe the types, stages, morphology and complications of lobar pneumonia. 4 mark(s)
Answer
(a) Definition: Pneumonia is an acute inflammation of the lung parenchyma (alveoli and/or interstitium) caused most commonly by infectious agents (bacteria, viruses, fungi), resulting in consolidation of the affected lung tissue.
(b) Lobar pneumonia — types, stages, morphology, complications:
Types: Lobar pneumonia most commonly involves an entire lobe of the lung uniformly, classically caused by Streptococcus pneumoniae (pneumococcus); it is contrasted with bronchopneumonia (patchy, multifocal, centred on bronchi/bronchioles).
Stages (classical 4 stages, over about a week):
- Congestion (Day 1): Lung is heavy, red, and boggy. Microscopically shows vascular congestion, intra-alveolar fluid with few neutrophils, and numerous bacteria.
- Red hepatization (Days 2–3): Lung looks liver-like (red, firm, airless). Alveoli are packed with neutrophils, red cells, and fibrin — giving a red, solid, “hepatized” gross appearance.
- Grey hepatization (Days 4–6): Lung remains firm but turns grey-brown as red cells break down; alveoli contain a fibrinosuppurative exudate of neutrophils and fibrin, with progressive disintegration of red cells.
- Resolution (Day 8 onward): Exudate within the alveoli is enzymatically digested and either resorbed, coughed up, organized by fibroblasts, or cleared by macrophages, restoring normal lung architecture.
Complications:
- Abscess formation
- Empyema (pus in the pleural cavity)
- Pleuritis/pleural effusion
- Organization (“carnification” — conversion of exudate to fibrous tissue)
- Bacteraemia with metastatic spread (meningitis, arthritis, endocarditis)
- Respiratory failure/ARDS in severe cases