Pleural Effusion

Key Features

Essentials of Diagnosis

• May be asymptomatic

• Chest pain occurs in the setting of pleuritis, trauma, or infection

• Dyspnea is common with large effusions

• Dullness to percussion and decreased breath sounds over the effusion

• Radiographic evidence of pleural effusion

• Diagnostic findings on thoracentesis

General Considerations

• Pleural fluid is produced at 0.01 mL/kg body weight/hour; a normal volume in the pleural space is 5–15 mL

• Transudative effusions (see Laboratory Tests) occur in the absence of pleural disease; heart failure accounts for the majority of cases

• Exudative effusions are most commonly due to pneumonia (parapneumonic effusions) and malignancy (malignant effusions)

• Analysis of pleural fluid allows for identification of five pathophysiologic processes leading to accumulation of pleural fluid

  • Increased production due to increased hydrostatic or decreased oncotic pressures (transudates)

  • Increased production due to abnormal capillary permeability (exudates)

  • Decreased lymphatic clearance of fluid (exudates)

  • Infection in the pleural space (empyema)

  • Bleeding into the pleural space (hemothorax)

• A definitive diagnosis is made through cytology or identification of causative organism in 25% of cases

• In 50–60% of cases, classification of the effusion leads to a presumptive diagnosis

• Diagnostic thoracentesis should be performed whenever there is a new pleural effusion and no clinically apparent cause

Clinical Findings

Symptoms and Signs

• Dyspnea, cough, or chest pain with respirations

• Symptoms are more common in patients with underlying cardiopulmonary disease

• Large effusions are more likely to be symptomatic

• Bronchial breath sounds and egophony above the effusion are caused by compressive atelectasis

• Massive effusions may cause contralateral shift of the trachea and bulging of intercostal spaces

• A pleural friction rub indicates infarction or pleuritis

Differential Diagnosis

• Atelectasis

• Chronic pleural thickening

• Lobar consolidation

• Subdiaphragmatic process

• Table 9–23

Diagnosis

Laboratory Tests

• Pleural fluid should be sent for

  • Protein

  • Glucose

  • Lactate dehydrogenase (LD)

  • Cell count

  • Gram stain

  • Culture

• Exudates have one or more of the following

  • Pleural fluid protein/serum protein > 0.5

  • Pleural fluid LD/serum LD > 0.6

  • Pleural fluid LD more than two-thirds of the upper limit of normal serum LD

• Bacterial pneumonia, cancer, and tuberculosis (in endemic regions) are the most common causes of ...