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| | [[Image:Acute pneumonia - i -- low mag.jpg|thumb|Acute pneumonia. [[H&E stain]]. (WC)]] |
| '''Pneumonia''' is inflammation of the lung, which includes infectious and non-infectious etiologies. | | '''Pneumonia''' is inflammation of the lung, which includes infectious and non-infectious etiologies. |
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| It is a subset of the [[medical lung diseases]]. This article primarily deals with the infectious pneumonias. Idiopathic interstitial pneumonias are discussed very briefly; they are dealt with in detail in the ''[[diffuse lung diseases]]'' article. | | It is a subset of the [[medical lung diseases]]. This article primarily deals with the infectious pneumonias. |
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| | Idiopathic interstitial pneumonias are listed at the bottom; they are dealt with in detail in the ''[[diffuse lung diseases]]'' article. |
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| =Infectious pnemonia= | | =Infectious pnemonia= |
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| ==Acute infectious pneumonia== | | ==Acute infectious pneumonia== |
| ===General===
| | {{Main|Acute infectious pneumonia}} |
| *This is seen by pathologists, in [[autopsy]], from time-to-time.
| | The most common form of pneumonia. It is usually diagnosed clinically. |
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| Most common cause:
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| *''Streptococcus pneumoniae''.<ref name=Ref_PBoD8_711>{{Ref PBoD8|711}}</ref>
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| The top three community acquired (acute) pneumonia:<ref name=pmid12239229>{{Cite journal | last1 = Nicolau | first1 = D. | title = Clinical and economic implications of antimicrobial resistance for the management of community-acquired respiratory tract infections. | journal = J Antimicrob Chemother | volume = 50 Suppl S1 | issue = | pages = 61-70 | month = Sep | year = 2002 | doi = | PMID = 12239229 }}</ref>
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| *''Streptococcuc pneumonia''.
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| *''Haemophilus influenzae''.
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| *''Moraxella catarrhalis''.
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| Other community acquired pneumonia:<ref name=Ref_PBoD8_711>{{Ref PBoD8|711}}</ref>
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| *S. aureus.
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| *Legionaella pneumophila.
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| *Klebsiella pneumoniae.
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| *Pseudomonas.
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| Hospital-acquired pneumonia:<ref name=Ref_PBoD8_711>{{Ref PBoD8|711}}</ref>
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| *Gram-negative rods.
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| *''Staphylococcus aureus''.
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| ===Radiologic correlate===
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| *Air space disease.
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| ===Gross pathology===
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| *Consolidation (the lung parenchyma is firm) - best appreciated by running a finger over the cut surface of the lung with a small-to-moderate amount of pressure.
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| Bronchopneumonia:
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| *Classically yellow-white centered on the bronchi.<ref>{{Ref AoGP|93}}</ref>
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| Lobar pneumnia is classically described in four stages:<ref>{{Ref AoGP|92}}</ref><ref>URL: [http://www.histopathology-india.net/Lobar_Pneumonia.htm http://www.histopathology-india.net/Lobar_Pneumonia.htm]. Accessed on: 27 February 2012.</ref>
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| #Congestion - day 1-2.
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| #Red hepatization - day 2-4.
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| #Gray hepatization - day 4-6.
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| #Resolution - day 6+.
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| Note:
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| *The stages of lobar pneumonia is considered more-or-less historical. In the age of antibiotics, lobar pneumonia is uncommon.
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| ===Microscopic===
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| Features:
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| *Alveoli packed with [[PMN]]s.
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| *+/-Clusters of bacteria - small dots or rods.
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| *+/-Abscess formation.
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| **Lung abscess = destruction of parenchyma + PMNs.<ref name=Ref_AoGP95>{{Ref AoGP|95}}</ref>
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| Image:
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| *[http://commons.wikimedia.org/wiki/File:Pneumonia_alveolus.jpg Normal alveoli & pneumonia (WC)].
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| ===Stains===
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| *Gram stain -- to type the bacteria.
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| ==Chronic infectious pneumonia== | | ==Chronic infectious pneumonia== |
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| *+/-[[Granuloma]]s. | | *+/-[[Granuloma]]s. |
| ==Aspiration pneumonia== | | ==Aspiration pneumonia== |
| ===General===
| | {{Main|Aspiration pneumonia}} |
| *Not associated with microorganisms - though empiric antibiotics are relatively common to cover infectious pneumonias that cannot be excluded easily on clinical grounds.<ref name=pmid21263315>{{Cite journal | last1 = Raghavendran | first1 = K. | last2 = Nemzek | first2 = J. | last3 = Napolitano | first3 = LM. | last4 = Knight | first4 = PR. | title = Aspiration-induced lung injury. | journal = Crit Care Med | volume = 39 | issue = 4 | pages = 818-26 | month = Apr | year = 2011 | doi = 10.1097/CCM.0b013e31820a856b | PMID = 21263315 }}</ref>
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| *Usually seen in the context of a toxin and/or pathology that affects the swallowing and cough reflexes.<ref name=pmid16082150>{{Cite journal | last1 = Ohrui | first1 = T. | title = Preventive strategies for aspiration pneumonia in elderly disabled persons. | journal = Tohoku J Exp Med | volume = 207 | issue = 1 | pages = 3-12 | month = Sep | year = 2005 | doi = | PMID = 16082150 }}</ref>
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| Common associations:<ref name=pmid16082150/>
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| *[[Stroke]].
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| *[[Multiple sclerosis]].
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| *[[Alcohol]] intoxication.
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| Other risk factors:<ref name=pmid21263315/>
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| *Traumatic brain injury.
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| *Seizure disorder.
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| *Bowel obstruction.
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| *Drugs.
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| *[[Obesity]].
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| *Labour.
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| Note:
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| *A special type of aspiration pneumonia is ''lipoid pneumonia''. It is dealt with in the ''[[lipoid pneumonia]]'' article.
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| ===Gross===
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| *More common in the right lung.
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| **Right main stem bronchus is more vertical.
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| ===Microscopic===
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| Features:
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| *+/-Foreign body giant cells.
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| *Microorganisms.
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| Images:
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| *[http://commons.wikimedia.org/wiki/File:Aspiration_pneumonia_%281%29.jpg Aspiration pneumonia - 1 - (WC)].
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| *[http://commons.wikimedia.org/wiki/File:Aspiration_pneumonia_%282%29.jpg Aspiration pneumonia - 2 - (WC)].
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| *[http://commons.wikimedia.org/wiki/File:Aspiration_pneumonia_%283%29.jpg Aspiration pneumonia - 3 - (WC)].
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| ==Cytomegalovirus pneumonia== | | ==Cytomegalovirus pneumonia== |