Bilateral Pleural Effusion

Toms Franquet, MD, PhD

DIFFERENTIAL DIAGNOSIS

Common

Congestive Heart Failure
Postcardiac Injury Syndrome
Infection
Renal Disease
Metastatic Malignant Pleural Disease
Lymphoma
Trauma/Iatrogenic
Lupus Pleuritis
Abdominal Surgery

Less Common

Asbestos-related Pleural Disease
Pregnancy-related

Rare but Important

Diffuse Pulmonary Lymphangiomatosis
Venoocclusive Disease
Drug-induced Pleuritis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Congestive heart failure (CHF) leading cause of bilateral pleural effusion
Small pleural effusions are not readily identified on conventional chest radiographs
- Meniscus sign on PA radiograph (> 200 mL)
- Pleural effusions can be entirely overlooked on supine radiographs
- Lateral decubitus chest radiograph: Useful for detecting small pleural effusions if clinically indicated
CT scans
- Should be performed with contrast enhancement
- No reliable distinction between exudates and transudates
- Can usually differentiate between benign and malignant pleural thickening
CT criteria for differentiating pleural fluid from ascites
- Interface sign: Fluid outside diaphragm is pleural; inside diaphragm, ascites
- Diaphragm sign: Indistinct interface between pleural effusion and liver owing to diaphragm
- Displaced-crus sign: Crus is anteriorly and laterally displaced from spine by pleural effusion
- Bare-area sign: Pleural fluid may extend behind liver at level of bare area

Helpful Clues for Common Diagnoses

Congestive Heart Failure
- Pulmonary venous hypertension essential for pleural fluid development
- Cardiomegaly, pulmonary vascular congestion, interstitial and alveolar edema
- Pleural effusion mainly derives from excess interstitial pulmonary fluid
- Bilateral effusions, relatively equal size
Postcardiac Injury Syndrome
- Combination of pericarditis, pleuritis, and pneumonitis after variety of myocardium and pericardium injuries
  - Post-myocardial infarction syndrome (Dressler syndrome)
  - Post-pericardiotomy syndrome: Pleuropulmonary reaction following extensive pericardiotomy
- Pleural effusion (80%): Bilateral or unilateral with nearly equal frequency
Infection
- Loculation suggests empyema
- Large effusions suggest anaerobic, gram-negative organisms, or S. aureus
Renal Disease
- Nephrotic syndrome
  - Due to hypoalbuminemia, hypervolemia, and increased hydrostatic pressures
  - Commonly subpulmonary and recurrent
Metastatic Malignant Pleural Disease
- Lung, breast, ovary, and stomach
- Unexplained pleural effusion in patient with malignancy
- CT: Irregular pleural thickening and small nodules (implants)
  - Metastases may have variable enhancement
Lymphoma
- Bilateral pleural effusion in 50%
- Chylothorax occasionally encountered
Trauma/Iatrogenic
- Hemothorax
  - Blunt or penetrating chest trauma
- Esophageal perforation
  - Causes: Idiopathic, iatrogenic, traumatic, and neoplastic
  - Clinically may simulate myocardial infarction or acute aortic dissection
  - Extraluminal air and bilateral pleural effusions
Lupus Pleuritis
- > 50% of patients with SLE will have pleural disease at some time in course of their disease
- Pleural disease usually painful
- Exudative pleural effusion usually small, either bilateral or unilateral
Abdominal Surgery
- Small early effusions common within 3 days after surgery (70%); bilateral (63%)
- Clinically not significant
- Predisposing factors: Upper abdominal surgery and postoperative atelectasis

Helpful Clues for Less Common Diagnoses

Asbestos-related Pleural Disease
- In approximately 3% of asbestos-exposed individuals
- Unilateral or bilateral and generally of small volume (< 500 mL)
- Over 50% asymptomatic
- As early as 1 year after exposure (mean latency = 30 years)
- May predispose to rounded atelectasis
Pregnancy-related
- Antenatally and in immediate postnatal period
- Normal finding on chest radiograph within 24-48 hours of delivery
  - Small and bilateral
  - Due to hypervolemia and high intrathoracic pressures from Valsalva maneuvers

Helpful Clues for Rare Diagnoses

Diffuse Pulmonary Lymphangiomatosis
- Rare disease of lymphatic system affecting individuals under 20 years; progressive disease with poor prognosis
- Term used when abnormalities are restricted to chest
  - CT: Thickening of interlobular septa, infiltration of mediastinal fat, areas of ground-glass opacity, and uni- or bilateral chylous effusions
Venoocclusive Disease
- Rare cause of pulmonary hypertension affecting postcapillary (venous) pulmonary circulation
- CT features: Smooth interlobular septal thickening, ground-glass opacity, and enlarged central pulmonary arteries with normal-caliber veins
- Moderate to small bilateral pleural effusions
Drug-induced Pleuritis
- Number of medications may cause exudative pleural effusions: Amiodarone, nitrofurantoin, phenytoin, methotrexate, cyclophosphamide, and carbamazepine
- Full list at http://www.pneumotox.com