Developmental stages of parapneumonic effusion and empyema: Diagnosis and management

Stage	Stage 1 (uncomplicated/simple)	Stage 2 (complicated/fibropurulent*)	Stage 3 (complicated/organizing*)
Timing	Early (days)	Late (days to weeks)	Late (weeks to months)
Pleural fluid characteristics	Exudative characteristics^¶ Low to moderately elevated WBC LDH level <1000 international units/L Normal pH and glucose levels No bacterial organisms	Exudative characteristics^¶ High WBC LDH >1000 international units/L pH <7.20 Glucose <40 mg/dL (2.2 mmol/L) OR Bacterial organisms present	Fluid may be difficult to obtain Bacterial organisms may or may not be present
Imaging characteristics	Generally small to moderate in size Free-flowing	Generally large and free-flowing, loculated, and/or with associated pleural thickening with contrast enhancement	May be large, loculated, and/or with pleural thickening (may be extensive and demonstrate a pleural rind) Pleural calcification may be evident^Δ
Treatment	Typically resolves with antibiotic therapy alone Drain if symptomatic	Antibiotics PLUS drainage^◊ Fibrinolytics/DNase may be required^§	Antibiotics PLUS drainage Fibrinolytics/mucolytics or VATS may be required^§^¥

This table displays the developmental characteristics of parapneumonic effusion and empyema. Prompt diagnosis and treatment is essential to the successful management of parapneumonic effusions. Chest computed tomography plays a vital role in evaluating the response to therapies.

WBC: White Blood Cell; LDH: Lactate dehydrogenase; VATS: video-assisted thoracic surgery.
* A complicated parapneumonic effusion (no frank pus) or an empyema (frank pus) can present in either stage 2 or 3 depending on pleural fluid coagulation characteristics and duration of bacterial persistence in the pleural space. Not all patients who have a complicated parapneumonic effusion progress to empyema. Importantly, while the identification of micro-organisms is helpful, abnormal chemistries alone are generally sufficient for the diagnosis.
¶ Exudative uncomplicated parapneumonic effusions are generally neutrophilic and have an elevated protein level >0.5 that of serum and/or a LDH level >0.6 that in the serum.
Δ After thoracentesis, air may be seen in the pleural space. While this may suggest trapped lung (indicating organization), air introduced during thoracentesis and gas-producing organisms (rarely) can also cause this finding.
◊ Complex effusions with multiple loculations may need more than one drain.
§ Complicated parapneumonic effusions tend to be more responsive to fibrinolytics/DNase in stage 2 than in stage 3.
¥ Stage 3 complicated parapneumonic effusions are more likely to need VATS than stage 2 effusions.

Graphic 121162 Version 1.0

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Developmental stages of parapneumonic effusion and empyema: Diagnosis and management