Complications of Pneumonia: Pleural Effusions
Oren Kupfer, MD, and Paul C. Stillwell, MD, FAAP
Introduction/Etiology/Epidemiology
•Pleural effusion is an abnormal amount of fluid in the pleural space.
•Effusions are often categorized as exudates or transudates, depending on their protein content and chemistry (Table 62-1).
•There are multiple causes of pleural effusion, but in children, the most common is related to an underlying lung infection (Box 62-1).
•The effusions associated with pneumonitis are parapneumonic effusions; the potential infecting organisms are listed in Box 62-2.
| Table 62-1. Criteria for Exudates and Transudates in Pleural Effusions | ||
| Exudate | Transudate | |
| Protein level (g/dL) | >3.0 | <3.0 |
| Ratio of pleural fluid protein level to serum protein level | >0.5 | <0.5 |
| LDH level (U/L) | >250 | <250 |
| Ratio of pleural fluid LDH level to serum LDH level | >0.6 | <0.6 |
LDH, lactate dehydrogenase. To convert grams per deciliter to grams per liter, multiply by 10. To convert units per liter to microkatals per liter, multiply by 0.0167.
•The most common pathogens that cause parapneumonic effusions are Streptococcus species and Staphylococcus species (both methicillin-sensitive and methicillin-resistant Staphylococcus aureus).
•In almost half of effusions, no pathogen is found, and patients are treated empirically for streptococcal infection. Coverage for Staphylococcus should be considered, depending on the local prevalence of these organisms.
•Parapneumonic effusions are initially thin and fairly clear with a yellow color, and they are freely mobile in the pleural space; this is considered an exudative phase secondary to pleural inflammation and occurs in the initial 2–5 days of illness.
Box 62-1. Causes of Pleural Effusions in Children, Classified According to Exudate and Transudate
| Exudative Pleural Effusions | Transudative Pleural Effusions |
| Parapneumonic effusion | Congestive heart failure |
| Pulmonary embolism | Nephrotic syndrome |
| Neoplasm | Cirrhosis or liver failure |
| Collagen vascular disease | Acute glomerulonephritis |
| Trauma | Hypoproteinemia |
| Drug hypersensitivity | Myxedema |
| Lung transplant rejection | Sarcoidosis |
| Chylothorax | Peritoneal dialysis |
| Gastrointestinal diseases | |
| Lymphatic diseases | |
| Postcardiac surgery syndrome | |
| Acute chest syndrome (sickle cell disease) |
Box 62-2. Infections Associated with Parapneumonic Effusions in Children
| Bacterial Causes | Nonbacterial Infectious Causes |
| Aerobic | Viral |
| Streptococcus pneumoniae | Adenovirus |
| Staphylococcus aureus | Influenza |
| Streptococcus pyogenes | Parainfluenza viruses |
| Anaerobic | Parasitical |
| Bacteroides species | Paragonimus species |
| Peptostreptococcus species | Cysticercus species |
| Peptococcus species | Entamoeba histolytica |
| Fusobacterium species | |
| Atypical | Fungal |
| Mycoplasma pneumoniae | Coccidioides immitis |
| Actinomyces species | |
| Nocardia species | |
| Mycobacterium tuberculosis |
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