Pathology 101 - Pneumonia

Jorvi Intensive Care by jsade

Background Reading

For normal histology and anatomy of the lungs, view Pathology 101 - Pulmonary Tumours.
To learn how to diagnose patients with pneumonia, consider reviewing clinical examination of the respiratory system. To refresh yourself on the symptoms and treatment, take a look at a brief rundown on Pneumonia. As always, Michelle (@eleytherius) has provided us with a quick snapshot.


Host Defence Mechanisms of the Respiratory System
  • Physical Processes (e.g. Mucociliary escalator, particle expulsion, etc)
  • Chemical Barriers (e.g. Mucus secreting goblet cells, α1-antitrypsin, etc)
  • Cellular Mechanisms (e.g. Alveolar macrophages, NK Cells, etc)

Normal flora of the respiratory tract
  • Streptococcus pneumonia
  • Haemophilus influenza
  • Diptheroids
  • Staphylococcus aureus
  • Moraxella catarrhalis
  • Neisseria spp
Lower respiratory tract is normally sterile.

Pneumonia

Balancing Act
Aaron Sparshott

Ways to classify Pneumonia.
  • Pathological Classification (air-space spread & interstitial spread)
  • Morphological Classification
  • Clinical Classification
Types of Pneumonia by Aaron Sparshott

Lobar & Broncho-pneumonia by Aaron Sparshott.
Adapted with gross morphology images by Pulmonary Pathology.

    BACTERIAL PNEUMONIA
    Pathogenesis
    • Bacterial entry into alveoli and growth
    • Tissue injury - injury to mucocilliary apparatus
    • Inflammation - mΦs can be disrupted by EtOH, 
    • Filling of alveolar spaces, spread to proximal alveoli - congestion can exacerbate CHF
    • Systemic effects leading to fever and sepsis - G- (Endotoxin), G+ (cell wall) components
     Lobar Pneumonia
    • Typically bilateral, widespread 
    • Affects the young and healthy
    • Caused by very virulent organisms (most commonly due to Strep. pneumoniae)
    • Disease localized to an entire lobe of lung
    • Fibrino-suppurative consolidation
    4 Stages of Lobar Pneumonia
    1. Congestion (24 hours - 2 days) - vascular engorgement, intra-alveolar fluid, few nΦ
    2. Red Hepatization (2 - 4 days) - exudation, red cells, neutrophils and fibrin fill alveolar spaces
    3. Grey Hepatization (4 - 8 days) - disintegration of red cells, persistence of fibrinosuppurative exudate
    4. Resolution (after 8 days) - mΦs digest debris, organization by fibroblasts


    Bronchopneumonia
    • Affects the very young or old
    • Patchy parenchymal involvement
    • Multiple foci of consolidation 
    • Bilateral and often widespread


    Complications
    1. Empyema - spread to pleural cavity - fibrinosuppurative rxn
    2. Bacteremia dissemination - (e.g. IE, pericarditis, meningitis, etc)
    3. Abscess formation - tissue destruction + necrosis
    4. Organisation - convert regions to solid tissue
     CURD Guidelines for Severity (≥ 2 of the following → 36x risk of death)
    • Confusion
    • Urea >7 mmol/L
    • Respiratory rate >30 /min
    • Diastolic BP <60 mmHg 
    Special Pneumonias
    1. Viruses
    2. Mycoplasma
    3. Legionnaires (Legionella pneumophila / longbeachae / micdadei)
    4. Meliodosis (Burkholderia pseudomallei)
     A collection of Pneumonia Tutorials

    Aspiration Pneumonia

    Early Pneumonia

    Organizing Pneumonia

    Interstitial pneumonia

    Pneumocystis pneumonia

    Aspiration pneumonia in an infant

    References
    Videos are thanks to  . Material is sourced from my notes from pathology tutorials at UQ, and Robbin's Pathologic Basis of Disease. References for images are underneath the image.

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