L22. Pathology of Lung Infection (Pneumonia)

Question 1

What is pneumonia?

Answer 1

Inflammation of the lung parenchyma (lower respiratory lung inflammation) which is most often due to infectious means

Question 2

What is acute inflammation? What are the three key events?

Answer 2

A vascular reaction to some form of injury

1. Dilation
2. Increased vascular permeability
3. Infiltration

Question 3

What is acute inflammation? What are the three key events?

Answer 3

A vascular reaction to some form of injury

1. Dilation
2. Increased vascular permeability
3. Infiltration

Question 4

What are the major symptoms of pneumonia?

Answer 4

Shortness of breath
Pleuritic chest pain (depending on the type of pneumonia)
Often purulent sputum
If infective: then there is often fever

Question 5

What are the major symptoms of pneumonia?

Answer 5

Shortness of breath
Pleuritic chest pain (depending on the type of pneumonia)
Often purulent sputum
If infective: then there is often fever

Question 6

What are the causative organisms and the characteristics of the ‘classic’ pattern of acute inflammation in the lung?

Answer 6

The traditional bacteria (typical)

• aerobic and easy to grow
• S. pneumonia, Klebsiella, P. aeruoginosa, Legionella

Question 7

What are some atypical organisms that cause an atypical pattern of acute inflammation?

Answer 7

Mycoplasma and some viruses

Question 8

What are the two patterns of acute bacterial pneumonia?

Answer 8

Acute Bronchopneumonia

Acute Lobar pneumonia

Question 9

Which pattern of acute pneumonia is most common? Why?

Answer 9

Bronchopneumonia is far more common (causative organisms of the lobar pneumonia have been less effective in the antibiotic era)

Question 10

Which pattern of acute pneumonia is most common? Why?

Answer 10

Bronchopneumonia is far more common (causative organisms of the lobar pneumonia have been less effective in the antibiotic era)

Question 11

What is the difference between community acquired pathogens and hospital acquired?

Answer 11

Community acquired tend to be gram positives and normal flora and more susceptible to antibiotics

Hospital acquired tend to be gram negative and resistant to antimicrobials because they are equipped to replicating under the stress of high antibiotic use environments

Question 12

How is aspiration a cause of pneumonia?

Answer 12

Aspiration of gut contents and secretions and of upper respiratory tract secretions into the throat and into the respiratory tract can occur and cause pneumonia.

• a normal physiological process but more often and problematic for people with altered conscious levels
• important because anaerobic bacteria may be the cause

Question 13

What is the most important defence against lung infection (especially pnuemonia)?

Answer 13

A fully functional immune system

Question 14

What are some other compromised lung defense mechanisms? [5]

Answer 14

• loss of a cough reflex ( anaesthesia, NM diseases, etc)
• impairment of mucocilary action
• Accumulation of secretions (CF, bronchial obstruction)
• Interference with phagocytic or bactericidal actoin of alveolar macrophages (alcohol, smoking)
• Pulmonary congestion and oedema

Question 15

What are some other compromised lung defense mechanisms? [5]

Answer 15

• loss of a cough reflex ( anaesthesia, NM diseases, etc)
• impairment of mucocilary action
• Accumulation of secretions (CF, bronchial obstruction)
• Interference with phagocytic or bactericidal actoin of alveolar macrophages (alcohol, smoking)
• Pulmonary congestion and oedema

Question 16

What are some predisposing factors to bacterial pneumonia?

Answer 16

Smoking
Reduced cough
Debility and malnutrition
Bronchial obstruction
Immune Suppression
Hospitalisation
Surgery/anesthesia
Alcoholism
Viral infections (leads to secondary infections)

Question 17

What are some predisposing factors to bacterial pneumonia?

Answer 17

Smoking
Reduced cough
Debility and malnutrition
Bronchial obstruction
Immune Suppression
Hospitalisation
Surgery/anesthesia
Alcoholism
Viral infections (leads to secondary infections)

Question 18

What determines what type of acute bacterial pneumonia is labelled what? (lobar vs. bronco)

Answer 18

The distribution of inflammation

Question 19

What determines what type of acute bacterial pneumonia is labelled what? (lobar vs. bronco)

Answer 19

The distribution of inflammation

Question 20

What is the localisation of inflammation of lobar pneumonia? What does this imply about the organism?

Answer 20

Affects the entirety of the lob with NO area spared
- implies the pathogen is highly virulent and the inflammation and oedema is thus spread very rapidly through the whole lobe

Question 21

What are the most common causes of lobar pneumonia?

Answer 21

Streptococcus pneumonia followed by Haemophilus influenzae

Question 22

What are the most common causes of lobar pneumonia?

Answer 22

Streptococcus pneumonia followed by Haemophilus influenzae

Question 23

What are the distinguishing features/symptoms of lobar pneumonia?

Answer 23

The patient is more likely to experience pleuritis (as the inflammation spreads to the pleura) and you hear ‘bronchial breath sounds’ over the area

Question 24

What is the localisation of inflammation of lobar pneumonia? What does this imply about the organism?

Answer 24

Affects the entirety of the lob with NO area spared

• implies the pathogen is highly virulent and the inflammation and oedema is thus spread very rapidly through the whole lobe

Question 25

What are the distinguishing features/symptoms of lobar pneumonia?

Answer 25

The patient is more likely to experience pleuritis (as the inflammation spreads to the pleura) and you hear 'bronchial breath sounds' over the area

Question 26

What is the localisation of inflammation of bronchopneumonia? What does this imply about the organism?

Answer 26

A PATCHY distribution of inflammation: multiple discrete foci separated by areas of normal, uninflammed lung - implies the pathogen is not highly virulent - suggests that the inflammation starts at the terminal bronchioles and spreads out to the alveolar parenchyma

Question 27

Does bronchopneumonia only involve one lobe?

Answer 27

No it often involves multiple lobes and is often bilateral

Question 28

Does bronchopneumonia only involve one lobe?

Answer 28

No it often involves multiple lobes and is often bilateral

Question 29

Is there always a large distinction between the two types of acute bacterial pneumonia?

Answer 29

No | There is often a large overlap between their presentations and the type is often not relevant to clinical practice

Question 30

Is there always a large distinction between the two types of acute bacterial pneumonia?

Answer 30

No | There is often a large overlap between their presentations and the type is often not relevant to clinical practice

Question 31

Acute bacterial pneumonias cause the classical pathologic change of consolidation. Define consolidation

Answer 31

Where normal aerated lung tissue is filled with fluid or inflammatory cells making it non-compressible, firm to touch and more solid

Question 32

Acute bacterial pneumonias cause the classical pathologic change of consolidation. Define consolidation

Answer 32

Where normal aerated lung tissue is filled with fluid or inflammatory cells making it non-compressible, firm to touch and more solid

Question 33

What does consolidation look like macroscopically?

Answer 33

Pale and solid

Question 34

What are the histological features of consolidation for acute bronchopneumonia?

Answer 34

Inflammatory cells in the septa Inflammatory cells and exudate (pus) in the alveolar spaces and in the airways Increased blood flow - dilated vessels

Question 35

What are the histological features of consolidation for acute bronchopneumonia?

Answer 35

Inflammatory cells in the septa Inflammatory cells and exudate (pus) in the alveolar spaces and in the airways Increased blood flow - dilated vessels

Question 36

What are the two morphological classifications of consolidation in acute lobar pneumonia?

Answer 36

Red hepatisation: lung looks red and solid representing an earlier stage of pneumonia due to large amounts of haemorrhage Grey Hepatisation: later stages when polymorph (neutrophil) infiltrates take over the cellular population and the lung begins to look pale grey and solid

Question 37

What is a lung abscess?

Answer 37

A collection of pus in the lungs

Question 38

What are some causes of lung abcsess?

Answer 38

Aspiration (a common cause) Obstruction of the bronchial tree Haemotgenous seeding from an extra-pulmonary infection Some types of bacterial pneumonias (S. pyogenes, K.pneumonia, S.aureus) - especially in debilitated hosts Aspiration of foreign bodies Trauma (accidental or surgical)

Question 39

What are some causes of lung abcsess?

Answer 39

Aspiration (a common cause) Obstruction of the bronchial tree Haematogenous seeding from an extra-pulmonary infection Some types of bacterial pneumonias (S. pyogenes, K.pneumonia, S.aureus) - especially in debilitated hosts Aspiration of foreign bodies Trauma (accidental or surgical)

Question 40

What are some causes of lung abcsess?

Answer 40

Aspiration (a common cause) Obstruction of the bronchial tree Haematogenous seeding from an extra-pulmonary infection Some types of bacterial pneumonias (S. pyogenes, K.pneumonia, S.aureus) - especially in debilitated hosts Aspiration of foreign bodies Trauma (accidental or surgical)

Question 41

What are the features of viral pneumonia?

Answer 41

- No consolidation (do get oedema and extravasation of fluid) - Lymphocyte dominated - Can cause bronchiolitis and inflammation of the septa (not the alveoli) - Predisposes to secondary bacterial infections

Question 42

What are the features of viral pneumonia?

Answer 42

- No consolidation (do get oedema and extravasation of fluid) - Lymphocyte dominated - Can cause bronchiolitis and inflammation of the septa (not the alveoli) - Predisposes to secondary bacterial infections

Question 43

What is a major example of a virus that causes bronchiolitis?

Answer 43

Respiratory Syncytial Virus that causes infiltration of lymphocytes to the bronchial wall

Question 44

What are the two major chronic infections affecting the lower respiratory tract?

Answer 44

Bronchiectasis and pulmonary TB

Question 45

What is bronchiectasis?

Answer 45

The irreversible dilation of the large, cartilaginous containing airways (bronchi)

Question 46

What is the cause of the dilatation in bronchiectasis?

Answer 46

Scar tissue deposition around the bronchi and weakening of the bronchial wall by inflammation - mainly by a CHRONIC BACTERIAL INFECTION and this contributes to the pooling of secretions that cannot be cleared (exacerbates chronicity of infection)

Question 47

What is the cause of the dilatation in bronchiectasis?

Answer 47

Scar tissue deposition around the bronchi and weakening of the bronchial wall by inflammation - mainly by a CHRONIC BACTERIAL INFECTION and this contributes to the pooling of secretions that cannot be cleared (exacerbates chronicity of infection)

Question 48

What is an important predisposition to bronchiectasis?

Answer 48

Airway obstruction

Question 49

What is a very serious sequelae of bronchiectasis?

Answer 49

Cyst frmation

Question 50

Where are bronchi normally distributed? How is this different in bronchiectasis?

Answer 50

``` Normally bronchi (as cartilage containing airways) are at the centre of the lungs and reduce in number to the periphery. In bronchiectasis, the bronchi become so prominent and dilated they appear at the periphery ```

Question 51

Where are bronchi normally distributed? How is this different in bronchiectasis?

Answer 51

``` Normally bronchi (as cartilage containing airways) are at the centre of the lungs and reduce in number to the periphery. In bronchiectasis, the bronchi become so prominent and dilated they appear at the periphery ```

Question 52

What are some complications of bronchiectasis?

Answer 52

Copious offensive sputum Poor drainage of secretions = recurrent bacterial pneumonia and abscess formation Rupture of vessels in bronchial walls = haemoptysis Pulmonary fibrosis leading to RV failure (cor pulmonale) Cerebral abcessess Amyloidosis

Question 53

What is TB caused by? Give characteristics of the organsim

Answer 53

Acid fast mycobacterium TB that is spread by droplets, is aerobic

Question 54

What are the two main characteristics of TB infection?

Answer 54

1. Granulomatous inflammation: granulomas (type 4 sensitivity reaction) to wall of the infection which is impossible for the body to clear 2. Caseous necrosis: at the centre of the granulomas that destroys the tissue and parencyma

Question 55

What is a tubercle?

Answer 55

A basic inflammatory lesion characteristic to TB - an area of granulomatous inflammation and casesous necrosis and is often about 2 cm. As the disease progresses they can grow larger and even fuse

Question 56

What is primary TB?

Answer 56

Patten of TB that occurs upon first exposure to the bacterium. If most often occurs in young children and can be unsymptomatic and undetected

Question 57

What are clinical presentations of primary TB?

Answer 57

A mild, self limiting illness that is often subclinical

Question 58

Are there ares of granulomatous inflammation in primary TB? Explain

Answer 58

Granulomatous inflammation occurs at the PERIPHERY (usually in the midzone) with caseous necrosis = GHON FOCUS Drainage of the bacteria into the hilar lymph nodes causes them to caseate (white nodular appearances) Ghon Focus + Involved Node = GHON COMPLEX

Question 59

What happens to these ghon complexes in an immune healthy host?

Answer 59

Ghon complexes are controlled and completely heal off by fibrosis (often with some calcification)

Question 60

What is secondary TB? What causes it? [2]

Answer 60

Occurs in patients that have previously been infected with the bacterium and thus have a fully sensitised response to it. 1. Reactivation of the infection (usually decades later and due to some immunocompromisatin) 2. Reinfection

Question 61

What is the pathology of secondary TB?

Answer 61

Areas of granulomatous inflammation appear in the upper lobes = APICAL areas The extend of the tubercles and caseation is much more severe causing more damage CAVITATION occurs of the caseous necrosis where it erodes into the wall of the bronchus and discharges into the bronchial tree Dystrophic calcification

Question 62

What keeps the caseation limited?

Answer 62

walling off by fibrosis (scar formation) which is damaging to the lung tissue (decreases compliance)

Question 63

What are some complications of secondary pulmonary TB?

Answer 63

Progressive spread of caeseation into surrounding lung Erosion of blood vessels (haemoptysis) Erosion into bronchial tree (cavitation and spread) Pleural inflammation and fibrosis Lung scarring

Question 64

What is miliary TB?

Answer 64

Numerous small granulomas widely scattered in the lungs or other organs caused by dissemination of the TB via blood vessels (haemoatogenous spread) - small seed like - high mortality - both primary and secondary TB - can effect any organs