Lung
Infectious
Pneumonia


Topic Completed: 1 August 2011

Minor changes: 10 August 2020

Copyright: 2003-2020, PathologyOutlines.com, Inc.

PubMed search: Pneumonia [title] infection lungs general

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Pneumonia. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/lungnontumorinfectionsgeneral.html. Accessed September 19th, 2020.
Definition / general
  • Pneumonia is defined as any infection of lung parenchyma
  • Lung is #1 site for infections that cause lost workdays
  • Infection of lung is more frequent than any other visceral organ
  • Generally microorganisms are inhaled, but pneumonia may also occur through hematogenous spread or direct inoculation
Pathophysiology
  • Pneumonia is due to impairment of normal defense mechanisms or lowered host resistance
  • Normal defense mechanisms are nasal clearance (sneezing, blowing, swallowing), tracheobronchial clearance (mucociliary action) and alveolar clearance (alveolar macrophages)
  • Impairment is due to primary or acquired immunosuppression, suppression of cough reflex (drugs, virus, coma, anesthesia), injury to mucociliary apparatus (smoking, virus, Kartegeners syndrome), injury to macrophages (tobacco, alcohol, anoxia), pulmonary congestion / edema or accumulation of secretions (cystic fibrosis)
  • Note: viral pneumonia predisposes to bacterial pneumonia
Clinical features
  • Often divided into community acquired (Minerva Anestesiol 2011;77:196), hospital acquired (Clin Infect Dis 2010;51 Suppl 1:S42) and aspiration pneumonia
  • Common agents: Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Legionella pneumophila, Pseudomonas aeruginosa, coliforms
  • Complications: abscess, empyema, organization, sepsis, meningitis
  • Consolidation: exudative solidification of lung
  • Signs and symptoms of pneumonia: shortness of breath, fever, productive cough, malaise, friction rub (if fibrinous pleuritis)
  • Bronchopneumonia: patchy consolidation of lung centered on bronchi; may progress to lobar pneumonia; patterns of bronco- and lobar pneumonia may overlap
  • Lobar pneumonia: affects entire lung but now rare due to antibiotics; associated with increased virulence of organism or increased host vulnerability (infants, elderly); may be due to extension of existing bronchiolitis or bronchitis
Gross images

Images hosted on other servers:
Bronchopneumonia - various images Bronchopneumonia - various images Bronchopneumonia - various images Bronchopneumonia - various images

Bronchopneumonia - various images

Lobar pneumonia - various images Lobar pneumonia - various images

Lobar pneumonia - various images

Microscopic (histologic) description
  • Bronchopneumonia: neutrophils in bronchi, bronchioles and adjacent alveolar spaces; lipid pneumonia, if marked, has lipid laden macrophages
  • Lobar pneumonia: initially congestion with bacteria and few neutrophils; then red hepatization (grossly resembles liver) with massive congestion, neutrophils, fibrin; then gray hepatization with fibrinopurulent exudate and organization; then resolution with resorption of exudate
Microscopic (histologic) images

Contributed by Yuri Tachibana, M.D.
Alveolar exudate

Alveolar exudate



Images hosted on other servers:
Bronchopneumonia - various images Bronchopneumonia - various images Bronchopneumonia - various images Bronchopneumonia - various images

Bronchopneumonia - various images

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