85 - Pathology of Lung Infection

Question 1

Most important determinant of whether a lung infection becomes clinical or not

Answer 1

Intact immune system

Question 2

What causes classical pattern of pneumonia?

Answer 2

Traditional bacteria
- Aerobic bacteria, known to medicine for a long time (as can be cultured easily)
S pneumoniae, H influenzae, Klebsiella pneumoniae, P aerusinosa, Legionella pneumophila

Question 3

Strict definition of pneumonia

Answer 3

Inflammation of the lung

Question 4

Two patterns of acute bacterial pneumonia

Answer 4

Acute bronchopneumonia

Acute lobar pneumonia

Question 5

Most common form of acute inflammation of the lung

Answer 5

Acute bronchopneumonia

Question 6

Prototypical atypical bacteria causing pneumonia

Answer 6

Mycoplasma

Question 7

Patients with a much higher risk of G- bacterial pneumonia

Answer 7

Those who acquire it in a hospital

Question 8

When was acute lobar pneumonia more common?

Answer 8

Pre-antibiotic era

Question 9

Five principle defence mechanisms of the lung

Answer 9

Cough reflex
Mucociliary function
Secretion clearance
Alveolar macrophage phagocytic action
Clearance of fluid from pulmonary circulation

Question 10

Five principle ways in which lung defences can be subverted

Answer 10

Loss of cough reflex
Impairment of mucociliary function
Accumulation of secretions (EG: CF)
Interference with alveolar macrophage function
Pulmonary oedema/congestive heart failure

Question 11

How does bronchopneumonia present grossly?

Answer 11

Discrete patches of inflammation (spots), not necessarily limited by lobes.
Often bilateral.

Question 12

Where does bronchopneumonia begin?

Answer 12

In terminal bronchioles, hence multifocal distribution.

Question 13

How does lobar pneumonia begin?

Answer 13

Inflammatory oedema spreads throughout a lobe.

Indicative of a highly-pathogenic organism.

Question 14

Difference in virulence of organisms that cause bronchopneumonia and lobar pneumonia

Answer 14

Bronchopneumonia often caused by less-pathogenic pathogens.

Question 15

Most-common cause of lobar pneumonia

Answer 15

S pneumoniae

Question 16

Second-most-common cause of lobar pneumonia

Answer 16

H influenzae

Question 17

Pneumonia more likely to cause inflammation of the pleura

Answer 17

Lobar

Question 18

Difference in auscultation between bronchopneumonia and lobar pneumonia

Answer 18

Bronchial breath sounds heard over area of lobar pneumonia

Question 19

Consolidation

Answer 19

Filling of alveolar spaces with fluid or inflammatory cells. Lung becomes harder to compress, harder.

Question 20

*ALVEOLARSLIDE NO LABELS

Answer 20

ALVEOLAR SLIDE

Question 21

Appearance of a histological slide of acute bronchopneumonia

Answer 21

Exudate from inflammation moves from alveolar septa into alveolar space.
Alveolar spaces full of inflammatory cells, protein-rich exudate.
Areas of lots of neutrophils are full of pus.
Blood vessels are thicker, from vasodilation.

Question 22

What does bronchopneumonia lung consolidation look like grossly?

Answer 22

Pale, solid areas are areas of consolidation.

Question 23

What does lobar pneumonia consolidation look like grossly?

Answer 23

Entire lobe is pale, hard.
Red hepatisation initially, grey hepatisation develops over time (because consolidated lung apparently looks like a cut surface of a liver).

Question 24

Why does red hepatisation develop before grey hepatisation?

Answer 24

Because early lobar pneumonia involves more haemorrhage.

Becomes white as neutrophils infiltrate, form pus.

Question 25

How does a lobar pneumonia appear on a CXR

Answer 25

Pale, solid.

Question 26

Condition where puss-filled cavities form in lung

Answer 26

Lung abscess

Question 27

Abscess

Answer 27

A collection of pus

Question 28

``` Causes of lung abscesses 1 2 3 4 5 ```

Answer 28

Aspiration Obstruction of the bronchial tree Haematogenous seeding of the lung from an extra-pulmonary infection (EG: osteomyelitis) Certain kinds of bacterial pneumonia (S pyogenes, S aureus, Klebsiella pneumoniae) Acute bronchopneumonia in debilitated hosts.

Question 29

Most important cause of lung abscesses

Answer 29

Aspiration of vomit when supine, asleep.

Question 30

What should you search for when theres an abscess caused by obstruction?

Answer 30

Bronchial carcinoma

Question 31

Kind of infection from aspiration

Answer 31

Mixed anaerobic infection (bacteroides)

Question 32

Key difference between viral and bacterial pneumonias

Answer 32

Viral don't cause consolidation. | Exudate from viral is lymphocyte-rich. Exudate from bacterial is neutrophil-rich.

Question 33

Type of oedema from viral pneumonias

Answer 33

A lot of exudate, but not purulent consolidation.

Question 34

How do viral pneumonias predispose to secondary bacterial pneumonias?

Answer 34

Cytopathic - destroy epithelial cells. Cause death of epithelial cells within the upper and lower respiratory tract, predisposing to secondary bacterial infections and severe pulmonary oedema

Question 35

Aetiological agent leading to lymphocytic bronchiolitis

Answer 35

Viral, leading to pneumonia

Question 36

Bronchiectasis

Answer 36

Dilation of large, cartilage-containing airways. | Permanent, irreversible.

Question 37

What causes bronchiectasis

Answer 37

Scar tissue deposition around the bronchi, weakening of bronchial walls from inflammation.

Question 38

Gross appearance of bronchiectasis

Answer 38

``` Very dilated (almost cyst-like) bronchi. White sections surrounding bronchi (scar tissue) ```

Question 39

Aetiological agent leading to bronchiectasis

Answer 39

Chronic bacterial infection. Inflammatory exudate weakens bronchial wall. Scar tissue deposits, widens bronchi as it contracts. Pooling of secretion.

Question 40

``` Complications of bronchiectasis 1 2 3 4 5 6 ```

Answer 40

1) Copious, offensive sputum production 2) Poor drainage of secretions, leading to recurrent bacterial pneumonia and abscesses. 3) Ruputure of vessels in bronchial walls, leading to haemoptysis 4) Pulmonary fibrosis leading to cor pulmonale 5) Cerebral abscesses (haematogenous spread of pathogen from lungs to brain) 6) Amyloidosis (very rare)