Pneumonias
Definition : It is an acute inflammation of lungs parenchyma with consolidation distal to terminal bronchioles ( consisting of the respiratory bronchiole, alveolar ducts, alveolar sacs and alveoli ).It may be infective and non-infective.
Pathogenesis : Microorganism can enter into the lungs by following route after failure of defensive mechanism -
i. Inhalation of air microbes.
ii. Aspiration of the microbes from the nasopharynx or oropharynx.
iii. Haematogenous spread from a distant focus of infection such as - vector population, environmental characteristics.
iv. Direct spread from a adjoining site of infection.
Classification :
1. On the basis of anatomical regions -
i. Inhalation of air microbes.
ii. Aspiration of the microbes from the nasopharynx or oropharynx.
iii. Haematogenous spread from a distant focus of infection such as - vector population, environmental characteristics.
iv. Direct spread from a adjoining site of infection.
Classification :
1. On the basis of anatomical regions -
- Lobar Pneumonia
- Bronchopneumonia or Lobular Pneumonia
- Interstitial Pneumonia
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| Features of lobar and lobular pneumonia |
2. On the basis of clinical aspects -
- Community-acquire Pneumonia
- Health care-associated Pneumonia (Hospital acquired Pneumonia)
- Ventilator-associated Pneumonia
3. On the basis of etiology and pathogenesis -
- Bacterial Pneumonia (Lobar pneumonia, Lobular pneumonia )
- Viral Pneumonia (Primary atypical pneumonia)
- Fungal pneumonia ( Pneumocystis pneumonia, Aspergillosis, Mucormycosis, Candidiasis, Histoplasmosis, Cryptococcosis, Coccidioidomycosis, Blastomycosis)
- Non infective pneumonias ( Aspiration pneumonia, Hypostatic pneumonia, Lipid pneumonia)
LOBAR PNEUMONIA
Definition : Lobar pneumonia is an acute bacterial infection of a part of a lobe, the entire lobe or even two lobes of one or both the lungs.
Etiology : Types of lobar pneumonia are describe, on the basis of causative agent.
1. Pneumococcal pneumonia : Most common 90% total lobar pneumonia. Cause by streptococcus pneumoniae.
2. Staphylococcal pneumonia : Cause by staphylococcus aureus.
3. Streptococcal pneumonia : Cause Beta-haemolytic streptococci.
4. Pneumnia by gram-negative aerobic bacteria - Haemophilus influenzae, Klebsiella pneumoniae (Friedlander's bacillus), Pseudomonas, Proteus and Escherichia coli.
Morphological Features : Morphological features are divided into 4 phases -
1. Stage of congestion or initial phase
2. Red hepatisation or early consolidation
3. Grey hepatisation or late consolidation
4. Resolution Phase
1. Stage of congestion or initial phase
2. Red hepatisation or early consolidation
3. Grey hepatisation or late consolidation
4. Resolution Phase
1. Stage of congestion / Initial phase : It lasts for 1-2 days
Grossly : The affected lobe is enlarged, heavy, dark red and congested. Cut surface exudes blood stained frothy fluid.
Histologically :
i. Dilatation and congestion of the capillaries of the alveolar walls.
ii. Seen pale and eosinophilic oedema fluid in the air spaces.
iii. Few red cells and neutrophils found in the intra-alveolar fluid.
iv. Numerous bacteria also detected in gram's stained alveolar fluid.
2. Red hepatisation / Early consolidation : It lasts for 2-4 days. The term hepatisation is refers to liver like consistency of the affected part of the lung.
Grossly : The affected lobe is red, firm and consolidated. Cut surface of the involve lobe is air less and shows red-pink color, dry, granular and has liver like consistency. This stage together with serofibrinous pleurisy.
Histologically :
i. Oedema fluid is coverts into strands of fibrin.
ii. There is found cellular exudate of neutophils and red cells.
iii. Many neutrophil shows ingested bacteria.
iv. The alveolar septa are less prominent due cellular exudate.
3. Grey hepatisation / Late consolidation : It lasts for 4-8 days.
Grossly : The affected lobe is firm and heavy. The cut surface shows dry, granular and grey appearance with liver like consistency. Fibrinous pleurisy is prominent.
Histologically :
i. The fibrin strands are dense and more numerous.
ii. The cellular exudate of neutrophils and red cells are reduced but macrophages begins appear in the exudate.
iii. The cellular exudate are separated from the septal walls by a thin clear space.
iv. The organism found less in number as degenerated forms.
4. Resolution phase : This stage begins from 8th to 9th day and it complete in 1-3 weeks. Resolution proceeds in progressive manner.
Grossly :
i. Previous solid fibrinous constituents is liquefied by enzymatic action.
ii. Finally restoring the normal aeration in the affected lobe.
iii. Softening process is starts centrally and spread to the periphery.
iv. Cut surface shows grey-red or dirty brown and frothy, yellow, creamy fluid.
v. Pleural resolution also starts.
Histologically :
i. Macrophages founds in numerous quantity in the alveolar spaces, while neutrophils remains in few quantity. Many macrophages contain engulfed neutrophils and debris.
ii. Granular and fragmented strands of fibrin are seen due to progressive enzymatic digestion.
iii. Alveolar capillaries are engorged (overfull with blood).
iv. There is removal of cellular contents as well as cellular exudate from the air spaces by expectoration and mainly by lymphatics.
COMPLICATIONS : Normally severe complications are uncommon but these complication may appear in immunosuppressed patient.
1. Organisation : Growth of fibroblasts from the alveolar septa resulting in fibrosed, tough, airless leathery lung tissue. This type of post-pneumatic fibrosis is called carnification. It is seen in 3% of cases.
2. Pleural effusion : In five percent treated cases may developed pleural effusion. Pleural effusion usually resolves but sometime may undergo organisation with fibrous adhesion between visceral and parietal pleura.
3. Empyema : Less than 1% of treated cases may develop encysted pus in the pleural cavity called empyema.
4. Lung abscess : When there is secondary infection by other organism that may cause lung abscess. It is rare.
5. Metastatic infection : Sometime, infection of the lungs and pleural cavity may extend into the pericardium and the heart causing purulent pericarditis, bacterial endocarditis and myocarditis. And sometimes may develop otitis media, mastoiditis, meningitis, brain abscess and purulent arthritis.
CLINICAL FEATURES : The onset of lobar pneumonia is sudden and major symptoms are -
Grossly :
i. Previous solid fibrinous constituents is liquefied by enzymatic action.
ii. Finally restoring the normal aeration in the affected lobe.
iii. Softening process is starts centrally and spread to the periphery.
iv. Cut surface shows grey-red or dirty brown and frothy, yellow, creamy fluid.
v. Pleural resolution also starts.
Histologically :
i. Macrophages founds in numerous quantity in the alveolar spaces, while neutrophils remains in few quantity. Many macrophages contain engulfed neutrophils and debris.
ii. Granular and fragmented strands of fibrin are seen due to progressive enzymatic digestion.
iii. Alveolar capillaries are engorged (overfull with blood).
iv. There is removal of cellular contents as well as cellular exudate from the air spaces by expectoration and mainly by lymphatics.
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| Stages of lobar pneumonia |
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Features
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Lobar Pneumonia
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Lobular Pneumonia
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Interstitial Pneumonia
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Definition
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It is an acute bacterial infection
of a part of lobe or entire lobe or even two lobes of one or both the lungs.
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It is the infection of terminal
bronchioles that extend into the surrounding alveoli resulting in patchy
consolidation of lung.
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It is characterized by patchy
inflammatory changes generally confined to interstitial tissue without any
alveolar exudates.
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Etiology
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Pneumococci, Staphylococcal pneumonia.
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Staphylococci, Streptococci etc.
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Respiratory Syncytial Virus (RSV), Mycoplasma pneumoniae.
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Morphology
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Stage of congestion (1-2 days),
Red hepatisation (2-4 days),
Grey hepatisation (4-8 days),
Resolution (8-9 days)
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Patchy consolidation with central
granularity, alveolar exudate, thickened septa.
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Patchy to massive and widespread
consolidation of one or both the lungs.
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Clinical features
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Shaking, Chills, Fever, Malaise, Chest pain, Dyspnoea,
Tachycardia, Tachypnoea and Cyanosis.
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Shaking, Chills, Fever, Malaise, Chest pain, Dyspnoea,
Tachycardia, Tachypnoea and Cyanosis, Mottled patches lung in X-rays.
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Initially – Fever, Headache, Muscles pain.
Later – Dry, Hacking, Cough with retrosternal burning.
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Complications
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Organisation, Pleural effusion,
Empyema, Lung abscess, Metastatic infection.
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Organisation, Pleural effusion,
Lung abscess, Empyema.
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Interstitial fibrosis and
permanent damage.
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COMPLICATIONS : Normally severe complications are uncommon but these complication may appear in immunosuppressed patient.
1. Organisation : Growth of fibroblasts from the alveolar septa resulting in fibrosed, tough, airless leathery lung tissue. This type of post-pneumatic fibrosis is called carnification. It is seen in 3% of cases.
2. Pleural effusion : In five percent treated cases may developed pleural effusion. Pleural effusion usually resolves but sometime may undergo organisation with fibrous adhesion between visceral and parietal pleura.
3. Empyema : Less than 1% of treated cases may develop encysted pus in the pleural cavity called empyema.
4. Lung abscess : When there is secondary infection by other organism that may cause lung abscess. It is rare.
5. Metastatic infection : Sometime, infection of the lungs and pleural cavity may extend into the pericardium and the heart causing purulent pericarditis, bacterial endocarditis and myocarditis. And sometimes may develop otitis media, mastoiditis, meningitis, brain abscess and purulent arthritis.
CLINICAL FEATURES : The onset of lobar pneumonia is sudden and major symptoms are -
- Shaking chills.
- Fever.
- Malaise with pleuritic chest pain.
- Dyspnoea.
- Cough with expectoration (mucoid / purulent / bloody ).
- Tachycardia.
- Tachypnoea (fast breathing ).
- Cyanosis ( if the patient is severely hypoxaemic ).
- Neutrophilia.
- Blood cultures are positive (in 30% of cases).
- Chest X-rays shows consolidation.
- Sputum cultures and antibiotic sensitivity are most significant investigation.
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