eMedicine Specialties > Emergency Medicine > Pulmonary
Pneumonia, Empyema and Abscess: Differential Diagnoses & Workup
Updated: Nov 7, 2007
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Differential Diagnoses
| Pleural Effusion | Pneumonia, Viral |
| Pneumonia, Aspiration | Tuberculosis |
| Pneumonia, Bacterial | |
| Pneumonia, Immunocompromised | |
| Pneumonia, Mycoplasma |
Other Problems to Be Considered
Workup
Laboratory Studies
- A CBC with differential may reveal a leukocytosis and a left shift.
- Collect sputum for Gram staining, culturing, and sensitivity testing.
- If tuberculosis is suspected, acid-fast bacilli testing should be obtained.
- Blood culturing is also appropriate.
Imaging Studies
- Perform chest radiography to diagnose and differentiate pneumonia, pulmonary abscess, and empyema. Distinction of these conditions is important because lung abscesses and pneumonia require medical treatment, while empyema frequently requires definitive surgical therapy.
- On the chest radiograph, a lung abscess appears as a solitary cavitary area with an air-fluid level, which typically is present in a dependent portion of the lung.
- A surrounding patchy area of infiltrate aids in differentiating a pulmonary abscess from a cavitary lung cancer.
- On the chest radiograph, findings that suggest empyema, as opposed to lung abscess, include extension of the air-fluid level to the chest wall, extension of the air-fluid level across fissure lines, and a tapering border of the air-fluid collection.
- The costophrenic angle should be closely inspected on the chest radiograph to assess the presence of fluid that suggests effusion or empyema.
- On the chest radiograph obtained of the patient in an upright position, blunting of the costophrenic angle occurs when approximately 200 mL of fluid accumulates.
- A lateral chest decubitus radiograph, obtained with the patient on his or her side, reveals whether the pleural fluid is mobile and forms layers or whether it is loculated.
- To better assess any abnormal lung findings found on a chest radiograph, CT of the chest or ultrasonography is required. Ultrasonography is useful for needle-guided aspiration and drainage of a potential pleural effusion. When ultrasonography is not used to guide needle aspiration, the failure rate is 12-15%. CT of the chest can assess for pneumonia, lung abscess, tumor, pleural effusions and septations, other pleural diseases, or pleural thickening.
Other Tests
- Pulse oximetry - To assess oxygenation
- ABG analysis - To assess respiratory adequacy
- Transtracheal aspiration for culturing - If sputum findings are nondiagnostic
Procedures
- If a pleural effusion is present, a diagnostic thoracentesis should be performed, and the fluid should be analyzed for pH, lactate dehydrogenase, and glucose levels; specific gravity; and cell count with differential. Fluid is also sent for Gram stain, culture, and sensitivity.
- Gram stain, routine culture, and sensitivity, and acid-fast bacillus testing should also be performed.
- The fluid should be sent for cytology if cancer is suspected.
- The following findings are suggestive of an empyema or parapneumonic effusion that will need a chest tube for complete resolution:
- Grossly purulent pleural fluid
- pH level less than 7.2
- WBC count greater than 50,000 cells/µL (or polymorphonuclear leukocyte count of 1,000 IU/dL)
- Glucose level less than 60 mg/dL
- Lactate dehydrogenase level greater than 1,000 IU/mL
- Positive pleural fluid culture
- A pleural fluid marker currently being studied is tumor necrosis factor (TNF)–alpha. In patients who have pleural effusions, a TNF-alpha level higher than 80 pg/mL is suggestive of an empyema or complicated parapneumonic effusion.
More on Pneumonia, Empyema and Abscess |
| Overview: Pneumonia, Empyema and Abscess |
 Differential Diagnoses & Workup: Pneumonia, Empyema and Abscess |
| Treatment & Medication: Pneumonia, Empyema and Abscess |
| Follow-up: Pneumonia, Empyema and Abscess |
| References |
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Further Reading
Keywords
aspiration, lung abscess, pleural pus, penetrating chest trauma, esophageal rupture, inoculation of the pleural cavity, thoracentesis, chest tube placement, subdiaphragmatic abscess, paravertebral abscess, poor dentition, absent gag reflex, septic emboli, vasculitic disorders, cavitating lung malignancies, pulmonary cystic disease, needle compression, polymicrobial oral flora, Bacteroides species, Fusobacterium species, Peptostreptococcus species, Staphylococcus aureus, S aureus, MRSA, Mycobacterium tuberculosis, M tuberculosis, skin flora, Staphylococcus epidermis, S epidermis, pleural effusion
