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Pneumonia, Empyema and Abscess: Differential Diagnoses & Workup
Updated: Nov 25, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
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. Several radiographs are shown below.
Pneumococcal pneumonia complicated by lung necrosis and abscess formation.
A lateral chest radiograph shows air-fluid level characteristic of lung abscess.
A 54-year-old patient developed cough with foul-smelling sputum production. A chest radiograph shows lung abscess in the left lower lobe, superior segment.
A 42-year-old man developed fever and production of foul-smelling sputum. He had a history of heavy alcohol use, and poor dentition was obvious on physical examination. Chest radiograph shows lung abscess in the posterior segment of the right upper lobe.
Chest radiograph of a patient who had foul-smelling and bad-tasting sputum, an almost diagnostic feature of anaerobic lung abscess.
- 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 usually necessary. Ultrasonography is useful for needle-guided aspiration and drainage of a potential pleural effusion or empyema. When ultrasonography is not used to guide needle aspiration, the failure rate is 12-15%. Color Doppler ultrasonography can also assist in differentiating empyema from peripheral air-fluid pulmonary abscess. Chen et al reported in a retrospective study that identification of color Doppler ultrasonography vessel signals in pericavitary consolidation was useful and specific for identifying lung abscesses, with sensitivity of 94% and specificity of 100%.4
- CT of the chest can assess for pneumonia, lung abscess, tumor, pleural effusions and septations, other pleural diseases, or pleural thickening. Many clinicians recommend limiting the use of CT in children to reduce radiation exposure. Jaffe et al studied the utility of routine CT scanning in children and concluded that, while CTs detected more parenchymal abnormalities, the additional information did not alter management and it did not predict clinical outcome in patients who were being treated with chest tube drainage and fibrinolytics.5 The British Thoracic Society guidelines conclude that chest CT has no role in the routine identification of pleural collections in children.6 A lung abscess in an adult is shown in the image below.
A 42-year-old man developed fever and production of foul-smelling sputum. He had a history of heavy alcohol use, and poor dentition was obvious on physical examination. Lung abscess in the posterior segment of the right upper lobe was demonstrated on chest radiograph. CT scan shows a thin-walled cavity with surrounding consolidation.
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 |
| Multimedia: Pneumonia, Empyema and Abscess |
| References |
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References
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Further Reading
Keywords
empyema, empyema treatment, empyema causes, aspiration, lung abscess, lung abscess treatment, lung abscess causes, lung abscess symptoms, lung infection, pleural pus, subdiaphragmatic abscess, paravertebral abscess
