Disorders of the Pleura¶
Chapter 305 | Part 7: Disorders of the Respiratory System
KEY CLINICAL POINTS¶
- Pleural effusion is defined as an excess of fluid in the pleural space, with exudative effusions ( ≥ 1 of 3 criteria: PF/serum protein >0.5, PF/serum LDH >0.6, PF LDH >2/3 upper normal limit) requiring further investigation.
- Pleural effusions are classified as transudative (systemic factors) or exudative (local factors), with transudative effusions most commonly due to CHF, cirrhosis, or nephrotic syndrome.
- Diagnostic workup includes imaging (chest X-ray, CT, ultrasound), thoracentesis, and pleural fluid analysis (LDH, protein, glucose, cell count, cytology).
- Malignant pleural effusions are associated with poor prognosis (<6-month survival) and require cytologic evaluation, pleurodesis, or thoracoscopy for confirmation.
- Pneumothorax is gas in the pleural space, with spontaneous (primary/secondary) and traumatic types, requiring immediate intervention for tension pneumothorax.
1. DEFINITION & OVERVIEW¶
The pleural space lies between the lung and chest wall, containing a thin layer of fluid for lubrication. Pleural effusion occurs when fluid accumulates in excess. Pneumothorax is gas in the pleural space. Disorders include effusions (transudative/exudative) and pneumothorax (spontaneous/traumatic).
Table 305-1: Differential Diagnoses of Pleural Effusions¶
| Category | Differential Diagnoses |
|---|---|
| Transudative | Congestive heart failure, Cirrhosis, Nephrotic syndrome, Peritoneal dialysis, Superior vena cava obstruction, Myxedema, Urinothorax |
| Exudative | Neoplastic (metastatic, mesothelioma), Infectious (bacterial, TB, fungal, viral, parasitic), Pulmonary embolism, Gastrointestinal disease, Collagen vascular diseases, Post-CABG, Asbestos exposure, Sarcoidosis, Uremia, Meigs’ syndrome, Drug-induced pleural disease, Trapped lung, Radiation therapy, Hemothorax, Chylothorax |
Table 305-2: Disease-Specific Pleural Fluid Tests¶
| Suspected Disease | Tests |
|---|---|
| Pancreatic disease/esophageal rupture | Pleural fluid amylase |
| Drug-induced pleural disease (Nitrofurantoin, Dantrolene, etc.) | Pleural fluid eosinophils |
| Congestive heart failure | Pleural fluid NT-proBNP >1500 pg/mL |
| Suspected Disease | Tests |
|---|---|
| Chylothorax | Pleural fluid cholesterol/triglycerides >1.2 mmol/L |
| Hemothorax | Pleural fluid hematocrit >50% of peripheral blood |
| Tuberculosis | Pleural fluid ADA >40 IU/L or IFN-g >140 pg/mL |
1.1 Pleural Effusion¶
Exudative effusions ( ≥ 1 of 3 criteria: PF/serum protein >0.5, PF/serum LDH >0.6, PF LDH >2/3 upper normal limit) require further investigation. Transudative effusions are due to systemic factors (CHF, cirrhosis).
1.2 Pneumothorax¶
Spontaneous pneumothorax occurs without trauma (primary: apical blebs; secondary: lung disease). Traumatic pneumothorax results from chest injury. Tension pneumothorax is life-threatening with positive pleural pressure.
2. EPIDEMIOLOGY¶
1.5 million Americans develop pleural effusion annually. Most common presentations: dyspnea, chest pain. Exudative effusions (bacterial pneumonia, malignancy, PE) vs. transudative (CHF, cirrhosis). Pneumothorax: 100,000 cases/year in the US, 10% of patients with community-acquired pneumonia develop parapneumonic effusion.
2.1 Risk Factors¶
CHF, cirrhosis, nephrotic syndrome, malignancy, trauma, iatrogenic injury (e.g., thoracentesis, CABG), asbestos exposure, immunosuppression.
2.2 Demographics¶
Males > females; older adults for CHF, younger for TB/parapneumonic effusions. Chylothorax: trauma/surgery; hemothorax: trauma.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Fluid balance disrupted by hydrostatic-oncotic pressures. Exudative effusions: local factors (inflammation, malignancy, infection). Transudative: systemic (CHF, cirrhosis). Parapneumonic effusions: reactive or infected (10% develop empyema). Chylothorax: thoracic duct disruption. Malignant effusions: tumor-induced inflammation/obstruction.
3.1 Mechanisms¶
Hydrostatic pressure > oncotic pressure → fluid leakage. Inflammatory mediators, tumor cells, or infections alter pleural permeability.
3.2 Pathogenesis¶
Pleural fluid formation overwhelms lymphatic drainage. Infections (TB, bacteria) or malignancy cause exudation. Trauma/obstruction leads to transudation.
4. CLINICAL FEATURES¶
Symptoms: dyspnea (most common), chest pain, fever, cough. Signs: decreased breath sounds, dull chest wall tenderness. Complications: empyema, tension pneumothorax, recurrent effusions, malnutrition (chylothorax).
4.1 Exudative Effusions¶
Dyspnea disproportionate to effusion size. Pleural fluid: exudate (LDH >2/3 upper limit), often with infection/malignancy.
4.2 Transudative Effusions¶
Dyspnea due to volume overload. Pleural fluid: transudate (LDH <2/3 upper limit), often associated with CHF/cirrhosis.
5. DIFFERENTIAL DIAGNOSIS¶
Table 305-1 lists differential diagnoses. Key differentiators: pleural fluid LDH/protein gradient, glucose levels, cell count, and specific tests (e.g., amylase for pancreatic rupture).
5.1 Exudative vs. Transudative¶
Exudative: PF/serum protein >0.5, PF/serum LDH >0.6, PF LDH >2/3 upper limit. Transudative: none of these criteria.
5.2 Specific Causes¶
TB (ADA/IFN- γ ), malignancy (cytology), infection (Gram stain/culture), chylothorax (triglycerides), hemothorax (hematocrit).
6. INVESTIGATIONS & DIAGNOSIS¶
Chest imaging (CT/ultrasound), thoracentesis, pleural fluid analysis (LDH, protein, glucose, cell count, cytology). Algorithm: Figure 305-1. Criteria for exudative effusions ( ≥ 1 of 3).
6.1 Diagnostic Algorithm¶
- Determine transudate/exudate via thoracentesis. 2. For exudates: perform pleural fluid analysis (LDH, protein, glucose). 3. Specific tests based on clinical suspicion (e.g., amylase for pancreatic rupture).
6.2 Imaging¶
Chest X-ray (free fluid on decubitus), CT (loculations/septations), ultrasound (guidance for thoracentesis).
7. MANAGEMENT & TREATMENT¶
Transudative effusions: treat underlying cause (CHF, cirrhosis). Exudative effusions: thoracentesis, pleurodesis, or drainage. Malignant effusions: chemotherapy, pleurodesis, or indwelling catheter. Chylothorax: octreotide, low-fat diet, thoracic duct ligation. Pneumothorax: needle aspiration, chest tube, or surgery for tension.
7.1 Exudative Effusions¶
Thoracentesis for diagnosis. Pleurodesis (talc, doxycycline) for recurrent effusions. Chemical pleurodesis (talc, bleomycin) or surgical (thoracoscopy).
7.2 Malignant Effusions¶
Cytology confirmation. Symptomatic management: thoracentesis, indwelling catheter, or pleurodesis. Avoid chemotherapy if prognosis is poor (<6 months).
7.3 Pneumothorax¶
Immediate intervention for tension pneumothorax. Primary spontaneous: needle aspiration/tube drainage. Secondary: chest tube with drainage. Surgical decortication for empyema.
8. PROGNOSIS & COMPLICATIONS¶
Malignant effusions: poor prognosis (<6 months). Recurrent effusions: 50% of primary spontaneous pneumothorax. Complications: empyema, tension pneumothorax, chylothorax, malnutrition, immunosuppression.
8.1 Mortality¶
Tension pneumothorax: 50% mortality without intervention. Malignant effusions: <6-month survival. Chylothorax: malnutrition if untreated.
8.2 Long-term¶
Recurrent pleural effusions (20% of exudative cases). Chronic pleural thickening (mesothelioma, TB).
9. SPECIAL CONSIDERATIONS¶
Pregnancy: avoid thoracentesis in third trimester. Pediatrics: pleural effusions in children often due to infection/malignancy. Elderly: increased risk of complications (e.g., tension pneumothorax).
9.1 Iatrogenic¶
Post-CABG effusions (left-sided, bloody, eosinophilic). Iatrogenic injuries (thoracentesis, central lines).
9.2 Drug-Induced¶
Nitrofurantoin, dantrolene, methysergide: pleural effusions with eosinophilic fluid.
10. KEY POINTS & CLINICAL PEARLS¶
- Use exudate/transudate criteria (LDH/protein gradient) to guide workup. 2. Thoracentesis is critical for diagnosis and management. 3. Malignant effusions require cytologic confirmation. 4. Chylothorax: octreotide + low-fat diet. 5. Tension pneumothorax is a medical emergency. 6. Recurrent effusions may require pleurodesis or surgical intervention.