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300 Pleural Effusion and Empyema

Failure to improve after pneumonia, the classical physical signs,
and radiological evidence of pleural fluid are diagnostic.
Investigations
Imaging
• Plain chest radiography (upright views) should show obliteration of
the diaphragmatic margins (costophrenic angles) with pleural fluid
collections (Figure 46.3). Because up to 400 ml may be required
before these costophrenic angles are obscured in older children and
adolescents, further diagnostic imaging may be needed.
• The erect chest x-ray may show an air fluid level (Figure 46.4) if
there is lung collapse, an associated pneumothorax, and/or infec-
tion with anaerobic bacteria.
• Indistinct diaphragmatic contours merit lateral decubitus views
of the chest. This may show layering of fluid. The absence of free
layering on the decubitus films does not exclude the possibility of a
Figure 46.2: Empyema with extension forming subcutaneous abscess and
empyema necessitans. loculated pleural effusion.
• In moderate effusion, the radiograph may demonstrate displacement
The development of parapneumonic pleural effusions is gradual, of the mediastinum to the contralateral hemithorax, as well as scoliosis.
and progression to empyema occurs in three phases: • Free-flowing pleural effusions suggest less complicated parapneu-
1. Exudative stage, or acute phase: This stage is characterised by monic processes, which may not require extensive diagnostic and
increased permeability and a small serous fluid collection. At this therapeutic interventions.
stage, the pleural cavity fills with an abnormal amount of pleural fluid
• An ultrasound scan is a sensitive test and can also be used to
containing some pus from the infectious condition, contains mostly
localise loculated effusions and to guide targeted drainage.
neutrophils, and is often sterile.
• Computed tomography (CT) may identify the presence of consoli-
2. Fibrinopurulent stage: This second phase is marked by a thickening dated lung or fibrinous septations. In situations of complex fluid
of the fluid, the accumulation of fibrin—a fibrous, protein-based collections, chest CT imaging is the study of choice because it can
coagulant—in the cavity, and the formation of fibrin membrane detect and define pleural fluid and image the airways, guide inter-
deposition, which forms partitions or loculations within the pleural space.
ventional procedures, and discriminate between pleural fluid and
3. Organising stage, or chronic phase: If left untreated, the chronic chest consolidation.
phase begins, during which a pleural peel is created by the resorption
of fluid, forming a thick fibrous material that can entrap the lung • Viewing the pleural space by using a thoracoscope to examine its
parenchyma. characteristics may also help the diagnosis in complex cases.
Left untreated, the ET burrows through the parietal pleura, usually Other Investigations
into the chest wall, to form a subcutaneous abscess that eventually • Thoracocentesis is the standard diagnostic test. Aspirated pus or
may rupture through the skin and discharge spontaneously, forming an fluid should always be cultured; in a febrile patient, blood cultures
empyema necessitans (Figure 46.2).
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should be done also. Where the cause of the pleural effusion is
Clinical Features not clear or if the fluid is bloodstained, cytological investigation
For both pleural effusion and empyema, the most common preceding fac- should also be done.
tor is pneumonia. The usual presenting symptoms are a general discom- • Blood culture is obtained to assist in the identification of the
fort or uneasiness, with fever, cough, and dyspnoea with nasal flaring. offending organism. In paediatric patients, where sputum production
Depending on the underlying condition, there may also be is uncommon, identifying the cause of the pulmonary symptoms
haemoptysis, chest pain, night sweats, dehydration, and/or weight loss. early in the course of a pulmonary infection is difficult. However,
The inflammation of the pleural space may cause abdominal pain and with parapneumonic effusions, the patient may become bactaeremic
vomiting. Symptoms may be blunted, and fever may not be present in as the organism invades the pleural space, and a blood culture may
patients who are immunocompromised. reveal the organism.
In more progressive cases, the patient might develop very foul • Total serum protein.
breath or cough up bloody or offensive-looking sputum with a strong
fetid odour. There may be a history of TB contact or treatment for other • Total white cell blood count.
manifestations of Kaposi sarcoma. • Culture and serologic studies of the aspirated pleural fluid, which
Clinically, there is not much to differentiate a pleural effusion and may reveal bacterial, mycobacterial, and fungal isolates.
empyema. The usual findings are dullness to percussion, decreased
breath sounds, decreased vocal fremitus, and tracheal shift. These • Cell count and differential of aspirated pleural fluid are taken.
signs may vary, however, depending on the causative organism and Although the pleural fluid obtained at thoracentesis is typically
the duration of the illness. purulent, with an elevated white blood count (WBC) count and
Auscultation may reveal crackles, decreased breath sounds, and a predominance of leucocytes, an effusion evaluated early in the
possibly a pleural rub if the process is recognised before a large infectious process may well be more transudative, with a less cel-
amount of fluid accumulates. Dullness to percussion and decreased lular WBC and a differential that has fewer leucocytes predomi-
breath sounds are likely findings, but they are difficult to elicit in the nant. Regardless of the cell count and differential, the treatment
younger child, who, because of discomfort, may be less cooperative should be based on clinical course, pending the culture results.
with the examination. Cytokine analyses of pleural fluid have been performed in experi-