Pediatric Empyema Workup

Updated: Sep 30, 2016
  • Author: Peter H Michelson, MD; Chief Editor: Girish D Sharma, MD, FCCP, FAAP  more...
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Laboratory Studies

The following studies are indicated in empyema:

  • CBC count

  • Blood culture: Blood culture is obtained to assist in the identification of the offending organism. In pediatric patients, in whom sputum production is uncommon, identifying the cause of the pulmonary symptoms early in the course of a pulmonary infection is difficult. However, with parapneumonic effusions, the patient may become bacteremic as the organism invades into the pleural space, and a blood culture may reveal the organism.

  • Serum lactate dehydrogenase (LDH) level

  • Total protein level

  • Glucose concentration

  • Bacterial, mycobacterial, and fungal cultures

  • Serologic studies of the aspirated pleural fluid

  • pH level

  • Amylase concentration

  • Lipid stain or triglyceride level

  • Cell count and differential: Although the pleural fluid obtained at thoracentesis is typically purulent, with an elevated WBC count and a predominance of polymorphonuclear cells (PMNs), an effusion evaluated early in the infectious process may well be more transudative, with a less cellular WBC count and a differential that is less PMN predominant. Regardless of the cell count and differential, the treatment should be based on clinical course, pending the culture results. Cytokine analyses of pleural fluid have been performed in experimental settings and may prove to add prognostic value on the degree of inflammation present and may be beneficial in determining treatment course in the near future.


Imaging Studies

See the list below:

  • Radiologic evaluation is the primary tool for the diagnosis of a parapneumonic effusion. Standard chest radiography is the first step to assess for pleural fluid. See the image below.

    Radiographic imaging of a parapneumonic effusion m Radiographic imaging of a parapneumonic effusion may be useful in assessing the stage of the effusion and the type of drainage needed. In Figure A, the left heart border is obscured, and more than 50% of the left hemithorax is filled with an effusion, as evidenced by a fluid meniscus. In Figure B, the effusion is demonstrated to be fluid because it layers out on a decubitus film. In Figure C, the lateral radiograph again demonstrates the fluid meniscus and filling of the posterior sulcus. These findings suggest tube thoracostomy placement may be sufficient to drain this pleural process.
  • Examination should include upright views of the chest to examine the diaphragmatic margins, which are obliterated with pleural fluid collections. Because as much as 400 mL may be required before these costophrenic angles are obscured in older children and adolescents, further diagnostic imaging may be needed.

  • In cases in which the effusion is moderate, radiography may reveal displacement of the mediastinum to the contralateral hemithorax, as well as scoliosis.

  • Indistinct diaphragmatic contours merit lateral decubitus views of the chest.

  • Free-flowing pleural effusions suggest less complicated parapneumonic processes, which may not require extensive diagnostic and therapeutic interventions. Ultrasonography that reveals the absence of loculations suggests that effective treatment can be achieved without surgical intervention. The absence of free layering fluid on the decubitus films does not exclude the possibility of a loculated pleural effusion. [7]

  • Consider ultrasonography or CT imaging to identify the presence of consolidated lung or fibrinous septations. In patients with complex fluid collections, chest CT imaging has emerged as the study of choice. Chest CT imaging can be used to detect and define pleural fluid and image the airways, guide interventional procedures, and discriminate between pleural fluid and chest consolidation.


Other Tests

See the list below:

  • Pleural fluid polymerase chain reaction (PCR), latex agglutination (or counter immunoelectrophoresis [CIE] for specific bacteria) may be helpful if the cause of the infection cannot be ascertained from stain or culture results.



See the list below:

  • Thoracentesis can provide both significant diagnostic information and therapeutic relief for parapneumonic effusions.

  • The presence of pus establishes the presence of an empyema, and the determination of the Gram stain, cell differential, and chemistries helps to guide therapy.

  • Performing thoracentesis before the initiation of antibiotics increases the diagnostic yield of the fluid cultures and allows for more specific antimicrobial therapy.