Split Pleura Sign

Toms Franquet, MD, PhD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Not specific for empyema
- Can occur with other causes of loculated pleural fluid
CECT
- Enhancement of thickened inner visceral and outer parietal pleura
- Thickened visceral and parietal pleural layers separated by fluid
- Thickening of extrapleural fat

Helpful Clues for Common Diagnoses

Empyema
- Commonly associated with bacterial pneumonia
  - Gram positive bacteria (Staphylococcus aureus & Streptococcus pneumoniae): 50%
- Transformation of parapneumonic effusion (not infected) into complicated effusion (infected but not purulent) and into empyema (frank pus)
- CECT features
  - Pleural enhancement: Not seen in transudative effusions
  - High accuracy in differentiating empyema from lung abscess
Sterile Reactive Collection
- Smooth, thin pleural surfaces and homogeneous fluid density
Malignant Effusion
- Mesothelioma
  - Parietal and to lesser extent visceral pleura involvement
- Metastases: Most common from breast, ovary, lung, and malignant thymoma
- Pleural nodularity

Helpful Clues for Less Common Diagnoses

Hemothorax
- More uniform pleural thickening
Postsurgical
- Expected after lobectomy and pneumonectomy
Pleurodesis
- Often for malignant effusions
- High attenuation areas in posterior basal regions of pleural space
- Extension of talc deposits into fissures