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Pneumonia: Difference between revisions

Pneumonia (view source)

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=== Laboratory examination ===
=== Laboratory examination ===
In nosocomial pneumonia, [[sputum culture]], [[blood culture]], and [[Arterial blood gas|ABG]] are important to guide treatment. <abbr>[[C-reactive protein|CRP]]</abbr> and [[leukocytes]] are usually measured to monitor severity. [[Procalcitonin]] can be used to differentiate bacterial from non-bacterial causes.
In nosocomial pneumonia, [[sputum culture]], [[blood culture]], and [[Arterial blood gas|ABG]] are important to guide treatment. <abbr>[[C-reactive protein|CRP]]</abbr> and [[leukocytes]] are usually measured to monitor severity. [[Procalcitonin]] can be used to differentiate bacterial from non-bacterial causes.
There are rapid antigen tests of urine for detection of S. pneumoniae and legionella, which can be used for more complicated cases. This is usually not necessary in a typical case of CAP. Atypical bacteria can’t be cultured but the specific pathogen can be determined by serology or PCR.


=== Imaging of pneumonia ===
=== Imaging of pneumonia ===
The gold standard for diagnosis is the presence of a new lung shadow on chest x-ray in the setting of typical clinical features. In elderly typical lung symptoms are not necessary for diagnosis. The shadow classically conforms to one lobe and is associated with air bronchograms. The chest x-ray findings usually persist for weeks even after symptoms have cleared, so they’re usually not used for follow-up. Chest x-ray is negative in the first 24 – 48 hours. The sensitivity of chest x-ray for pneumonia is low, and so a negative x-ray does not rule it out, especially in the early phases.
The gold standard for diagnosis is the presence of a new opacity on [[chest x-ray]] in the setting of typical clinical features. The opacity is caused by the consolidation of the tissue, caused by presence of exudate in the alveoli. Chest x-ray is negative in the first 24 – 48 hours. The sensitivity of chest x-ray for pneumonia is low, and so a negative x-ray does not rule it out, especially in the early phases.The chest x-ray findings usually persist for weeks even after symptoms have cleared, so they’re usually not used for follow-up for pneumonia. CT may also visualise pneumonia but is unnecessary for uncomplicated cases.
 
The consolidation usually has indistinct margins, except if they are next to the pleura of interlobar fissures, where the margins will be sharp. It appears "fluffy". If the pneumonia is central, one can see hypodense bronchi in the consolidation, which are called air bronchograms.
 
Lobar pneumonia is the most common type, in which an entire lobe or almost an entire lobe is consolidated on imaging. Bronchopneumonia also exists, where there are multiple diffuse patchy opacities in one or both lungs.
 
In atypical pneumonia, chest x-ray may show patchy reticular opacities in the perihilar lung. CT can show also show the pathology, but CT is rarely necessary to make the diagnosis.  


In atypical pneumonia, chest x-ray can be negative. In these cases, CT can show characteristic changes. These bacteria can’t be cultured but the specific pathogen can be determined by serology or PCR.
In elderly typical lung symptoms are not necessary for diagnosis as they may have atypical symptoms.


There are rapid antigen tests of urine for detection of S. pneumoniae and legionella, which can be used for more complicated cases. This is usually not necessary in a typical case of CAP.
If a consolidation has been found on chest radiograph and a diagnosis of pneumonia has been made, a repeat radiograph should be made after resolution of the pneumonia to rule out [[lung cancer]].


=== Differential diagnosis ===
=== Differential diagnosis ===