Pathology of parenchymal lung disease

Question 1

what is parenchyma

Answer 1

parts of the lungs involved in gas transfers, including the alveoli, interstitium, blood vessels. bronchi and bronchioles

Question 2

what are the lungs defence mechanisms

Answer 2

ciliated epithelium
mucus
cough
IgA and antimicrobials in mucus
resident alveolar macrophages and dendritic cells
innate/adatptive immune responses

Question 3

what cells produce surfactant

Answer 3

type 2 pneumocytes (they also are the cells that proliferate in response to injury and differentiate into type 1 which are used for rapid gas transfer)

Question 4

describe pneumonia

Answer 4

caused by a variety of pathogens (bacteria, viruses, fungi)
many different categories - community acquired, hospital acquired, health care associated, aspiration associated, necrotising/abscess formation

Question 5

what causes community acquired pneumonia

Answer 5

main causes - streptococcal pneumoniae, haemophilus influenzae
other causes are moraxella catarrhalis, staphylococcus aureus, klebsiella pneumoniae, pseudomonas aeurginosa, mycoplasma pneumoniae

Question 6

describe hospital acquired/ healthcare associated

Answer 6

pneumonia that develops 48hrs after hospital admission
often associated with increased levels of antibiotic resistance

Question 7

describe aspiration associated pneumonia

Answer 7

someone who hasn’t got a safe swallow, someone vomiting and then swallowing, swallowing food
much more likely to be an anaerobic infection

Question 8

common causes of pneumonia

Answer 8

normally bacterial infections
among immunocompromised patients its usually atypical bacterial infections, viral or invasive fungal

Question 9

what are the five cardinal signs of inflammation

Answer 9

heat, redness, swelling, pain and loss of function

Question 10

how does swelling present in lung inflammation

Answer 10

oedema leads to a loss of gas exchange capacity, you then become hypoxic
changes in blood flow can also cause it
hypoxia can also cause loss of function

Question 11

describe bronchopneumonia

Answer 11

most common type
associated with strep pneumoniae
patchy and diffuse change, centres around the bronchus but spills out into surrounding space
often occurs in elderly with risk factors

Question 12

describe lobar pneumonia

Answer 12

associated with strep pneumonia
consolidation (fills with pus) of a large portion of a lobe, or an entire lobe
rust coloured sputum

Question 13

risk factors for developing pneumonia

Answer 13

distorted cilia function
abnormal mucus production
immunological deficiency
immunosuppressive agents
loss or suppression of the cough reflex
injury to mucociliary apparatus
accumulation of secretions
impaired alveolar macrophage function
pulmonary congestion/oedema

Question 14

complications of pneumonia

Answer 14

local - abscess formation, parapneumonic effusion (sterile, neutrophil rich), empyema (pus in pleural space)
bacteria in pleural space is difficult to reach via antibiotics, chest drain may be required
systemic - sepsis, acute respiratory distress syndrome, multiorgan failure ( liver, renal, cardiac etc)
in patients over 50 if it does not resolve think cancer

Question 15

what is ARDS

Answer 15

profound hypoxia in the context of diffuse x-ray changes not being due to pulmonary oedema
due to the local pathology within the lungs

Question 16

causes of ARDS

Answer 16

direct - pneumonia, aspiration, hyperoxia, ventilator associated injury
indirect - sepsis, systemic injury (RTA), pancreatitis, acute hepatic failure
associated with covid

Question 17

what does a cell in ARDS look like

Answer 17

neutrophils stuck in blood vessels
thickening of interstitium
dying alveolar epithelial cells
acute inflammation
extensive cell death
extensive oedema

Question 18

causes/features of chronic parenchymal inflammation

Answer 18

lung abscesses (bacteria/fungi)
vasculitis
rheumatoid arthritis
fungal infection

Question 19

what is a granuloma

Answer 19

structure formed during inflammation
collection of immune cells, principally macrophages
often occurs when you cant eliminate a substance
description not a diagnosis

Question 20

common causes of granulomatous inflammation

Answer 20

TB - mostly in the developing world
alcoholism
immunocompromised
diabetes

Question 21

primary TB

Answer 21

first 3-4 weeks tb multiplies within alveolar macrophages, however they cannot kill the infection
3-8 weeks - secrete things like interferons which cause macrophage and monocyte recruitment to form a local granulomatous response
activated lymphocytes further activate macrophages to kill, local necrosis occurs
in most people primary tb stops here

Question 22

primary prgressive tb

Answer 22

infection not arrested
often associated with immunocompromised
bronchopneumonia - infection spreads via bronchi, well developed granulomas don’t form
miliary tb - infection spreads via blood stream, affects multiple organisms

Question 23

secondary tb

Answer 23

reactivation of tb
could be due to becoming immunocompromised
see this principally at the apex of the lung, then develops locally
erodes into bronchus and cavities develop
may progress to bronchopneumonia

Question 24

other causes ofgranulomatous inflammation

Answer 24

other infection - fungi
sarcoidosis
rheumatoid arthritis

Question 25

other causes of granulomatous inflammation

Answer 25

other infection - fungi
sarcoidosis
rheumatoid arthritis
berrylosis
hypersensitivity pneumonitis
aspiration pneumonia
Langerhans cell histiocytosis

Question 26

describe sarcoidosis

Answer 26

autoimmune disease
multi-system, frequently involves the lungs and has a range of presentation
very responsive to steroid therapy
can look similar to tb

Question 27

fibrosing diseases of the lung

Answer 27

honeycomb lung - fibrosis
restrictive chronic lung disease
dyspnoea, cough, tachypnoea, crepitations, cyanosis (late stage
reduced transfer and total ung capacity on LFTs
ground glass changes in lower zones on x-rays