Medwiki

L8 Pathology Pneumonia

Topics covered

  • Definition and classification of pneumonia
  • Predisposing factors
  • Acute respiratory distress syndrome
  • Pathology of pneumonias
  • Bacterial pneumonia with examples
  • Viral pneumonia with examples
  • Pneumonia in an immunocompromised host

What is Pneumonia

Pneumonia is the inflammation of the lung parenchyma usually caused by an infective organism.

Classificaiton of pneumonia

the tree classifications are

  • By clinical setting
  • by causative organism
  • by morphology

Clinical setting

Community acquried Nosocomical (HAI i think) Immunocopromised Aspiration

Predisposing factors

  • decrease cough
  • injury to cilia
  • decreased alveolar macrophages
  • odema or congesiton
  • retention of secretion

all are things that stop clearing or defence of the lung

Acute respiratory distress syndrome

What is it?

Proliferative phase

1-3 weeks proliferaiton of type 2 pneumocytes macrophages

Fibrotic phase

resoluation with fibrossis repair/fibrosis honeycomb lung

ARDS sequence of response

ARDs lead to alveolar collapse

Acute ARDS leads to alveolar collapse due to damage to the type II pneumocytes, which means no surfactant

Bacterial pneumonia

Lobar pneumonia

Confluent consilidation involving a complete lung lobe infection through pores of khon

Most often due to Streptococcus pneumoniae

can be seen with other organisms (legionella)

Clinical setting

usually community acquired and classically affects young healthy adults

Pathology

classical acute inflammatory response

  • exudation of fibrin rich fluid
  • neutrophil infiltration
  • macrophage infiltration
  • resolution

Stages of Lobar pneumonia

  1. Congestion
    1. capillaries are congested and lung become oedematous
  2. red hepatisation
    1. red cells enter the alveolus
    2. bacteria are ingested by polymorphs
  3. grey hepatisation
    1. macrophages ingest and remove dead inflammatory cells and fibrous exudate
  4. resolution

Bronchopneumonia

This is where alveoli and bronchioles are the centre of infection so the consolidaiton is patchy and not confined by lobar architecture spreads thriough airways

Predisposing facotes

postviral depressed cough distal to obstruction aspiration immunosuppression cardiacfailure

causative organisms

Varied – Strep. Pneumoniae, Haemophilus influenza, Staphylococcus, anaerobes, coliforms

Clinical context may help. Staph/anaerobes/coliforms seen in aspiration

Viral pneumonia

We see congestion of the alveolar walls

late viral pneumonia has acute injury pattern similar to ARDS. acute inflammatory infiltration ess obvious. can see viral inclusions

Viral pneumonia causes

  • Influenza
  • RSV
  • Measles
  • Adenovirus
  • Coronaviruses

RSV can predispose to asthma coronaviruses kills via coronavirus storm

Influenza pneumonia can weaken the immune system and predispose to bacteria

Immunocomprimised subjects

  • primary immune deficiency
  • HIV/AIDS
  • Trauma
  • Diabetes mellitus
  • Secondary to treatment
    • treatment
    • chemo

Graph View