A 78-year-old previously healthy man presented with two days
of cough productive of thick purulent sputum, fever and dyspnea
On examination, he was an elderly man who appeared acutely ill.
Vital signs—blood pressure 96/60 mm Hg, pulse
116 beats/ min, respiratory rate 24 breaths/min, temperature
Lung examination revealed scattered ronchi, which were greater
on the right than the left.
Blood tests and a chest radiograph were obtained and intravenous antibiotics were administered.
- What do the chest radiographs show (Figure
One of the primary roles of chest radiography in emergency department
patients is to diagnose pneumonia. Although
the chest radiograph is abnormal in nearly all cases, early in its
course or with milder cases, the radiograph may be normal. Pneumonia
is, therefore, a diagnosis based on clinical, not radiographic,
findings. Radiography serves to confirm the diagnosis, to assess
prognosis (e.g., poorer outcome with multilobar pneumonia), and
to detect an underlying lesion such as a bronchogenic carcinoma
causing postobstructive pneumonia.
Patterns of Pneumonia
There are three pathological patterns of
pneumonia: lobar pneumonia, bronchopneumonia (lobular),
and interstitial pneumonia. This classification
is based on the pathogenesis of the infection and the histological
appearance of infected lung tissue. Each pattern is associated with
specific infecting organisms (Table 1).
Table 1 Pathological Patterns of Pneumonia ||Download (.pdf)
Table 1 Pathological Patterns of Pneumonia
|Organisms||Histopathology||Characteristic Radiographic Findings*|
|Lobar Pneumonia (segmental)
||Strep. pneumoniae, Klebsiella||Alveoli filled with purulent exudate, alveolar walls not thickened||Focal airspace filling|
||Staph. aureus, aspiration, Pseudomonas, tuberculosis
||Infection in bronchus spreads distally to segmental airspaces; also may spread proximally to affect other lung segments||Patchy, airspace filling—involving one segment or multifocal; abscess or cavity formation|
|Interstitial Pneumonia||Viral, Mycoplasma, Pneumocystis||Alveolar walls thickened by inflammatory cells, spreads to adjacent airspaces||Reticular or reticulonodular pattern; diffuse, patchy, or focal airspace filling|
Although these terms are often used to describe the radiographic
appearance of pneumonia, there is only limited correlation between
the infecting organism and radiographic pattern. For example, pneumococcal
pneumonia can have a patchy radiographic appearance simulating bronchopneumonia;
staphylococcal pneumonia can cause a relatively uniform segmental
consolidation; and viral pneumonia often spreads to the airspaces
and has an airspace-filling appearance. Radiographic findings are
therefore not used to predict the infecting organism or to choose
antibiotic therapy. Antibiotic therapy is based instead on clinical
parameters such as severity of illness, host factors such as immunologic
status, and clinical setting (community versus hospital acquired).