Lung Infections - Pneumonia

Question 1

Definition of pneumonia

Answer 1

• infective inflammation & consolidation of the lung
• filling of airspaces by inflammatory exudate - renders affected area solid & airless
• is a kind of pneumonitis = inflammatory disease dominated by interstitial inflammation (causes apart from infection include inhaled toxins & allergens, drug reactions, irradiation, connective tissue disease)

Question 2

Classification of pneumonia

Answer 2

1. Pathological - how infection spreads
   - bronchopneumonia
   - lobar pneumonia
2. Microbiological - causative organism
3. Clinical
   - CAP, HAP, special envts, disease in immunosuppressed patients, aspiration

Question 3

Features of bronchopneumonia

Answer 3

• primary infection centred on bronchi, spreads to involve adjacent alveoli
• infants, elderly, common terminal event in debilitated patients
• affects lower lobes more, secretions drain to the bottom, cannot be coughed out

Question 4

Complications of bronchopneumonia (3)

Answer 4

1. Lung abscess
2. Pleural infection
3. Septicaemia

Question 5

Morphology of bronchopneumonia

Answer 5

• G: patchy areas of consolidation, may become confluent

- M: acute inflammatory infiltration of bronchioles & adjacent alveoli

Question 6

Features of lobar pneumonia

Answer 6

• organisms gain entry to distal airspaces rather than colonising bronchi
• rapid spread through alveolar spaces & bronchioles - without following airways
• usually very virulent - Strep pneumonia, Klebsiella
• often causes severe illness + bacteremia
• prompt treatment can lead to complete resolution (little tissue destruction)

Question 7

Morphology of lobar pneumonia

Answer 7

• G: consolidation of whole/part of a lobe, liver-like consistency - hepatization (firm, airless)

M:

• alveoli of affected lobe diffusely infiltrated by acute inflammatory exudate (neutrophils, fibrin)
• red hepatization: massive confluent exudation with neutrophils, red cells, fibrin filling alveolar spaces
• grey hepatization: progressive disintegration of red cells & persistence of the original fibrinosuppurative exudate

Question 8

Features of community acquired pneumonia

Answer 8

• usually gram positive bacteria - commonly Strep pneumoniae

- also H. influenzae, Legionella, Mycoplasma, M. tuberculosis, viral

Question 9

Features of hospital acquired pneumonia

Answer 9

• mainly due to gram neg bacteria eg Klebsiella, E coli, Pseudomonas
• pts on mechanical ventilation are at risk
• investigation of sputum is often a problem due to colonisation - may req direct sampling of affected lung (BAL)

Question 10

Effects/complications of pneumonia (4)

Answer 10

1. Pleurisy
2. Lung abscess
3. Septicaemia
4. Lung fibrosis

Question 11

Features of aspiration pneumonia

Answer 11

• unconsciousness, impaired swallowing
• mixed organisms (often anaerobes, oropharyngeal bacteria) +/- gastric acid +/- food = infective pneumonia + chemical damage
• freq leads to lung abscesses, leaves cavities

Question 12

Features of atypical pneumonia

Answer 12

• minimal airspace exudate (no consolidation on CXR)
• marked infiltration of alveolar septa/interstitium by chronic inflammatory cells
• interstitial pattern pneumonia, not fought by neutrophils but lymphocytes