Etiology
- Infectious causes: (viral causes are often associated with transudative pleural effusions, and the others often have exudative pleural effusions)
- Viral (e.g., coxsackie, cytomegalovirus, Epstein-Barr virus, influenza): often associated with a transudative pleural effusion
- Bacterial (e.g., pneumonia [50% develop pleuritis], tuberculosis, Legionnaires disease, rickettsia)
- Parasitic (e.g., amebiasis)
- Fungal infections
- Liver or splenic abscesses
- Systemic causes: (often with transudative pleural effusions)
- Autoimmune disorders: rheumatoid arthritis (5% have pleuritis) or systemic lupus erythematosus (50% have pleuritis), others
- Inflammatory bowel disease
- Lung cancer, mesothelioma (from asbestos exposure), other malignancies involving the pleura
- Lymphoma
- Cystic fibrosis
- Cardiac problems (ischemia, pericarditis)
- Pancreatitis
- Traumatic or mechanical causes: (trauma often associated with hemothorax)
- Pneumothorax (90% develop pleuritis)
- Pulmonary embolism (5%–20% associated with pleuritis)
- Chest injuries (blunt or penetrating):
- Rib fracture
- Aortic dissection
- Disruption or obstruction of the thoracic duct, leading to accumulation of lymph in the pleural space (chylothorax)
- Medications:
- Amiodarone, bleomycin, bromocriptine, cyclophosphamide, methotrexate, procarbazine, hydralazine, procainamide, quinidine, etc.
Pathogenesis
- Anatomical pathology considerations:
- Pleural space: a potential space lined by a single layer of mesothelial cells supported by connective tissue
- Inflammation can cause inflammatory mediators to infiltrate the pleural space, causing the production of pleural fluid, which can be transudative or exudative; if frank pus is within the space, then it is called an “empyema,” which is different from an abscess because the neutrophils accumulate in a pre-formed space.
- Blood, air, or chyle can also enter the pleural space.
- Pain receptors
- Present on the parietal pleura
- Peripheral and lateral hemidiaphragm pleural membranes are innervated by intercostal nerves that also have cutaneous distributions.
- Peripheral and lateral hemidiaphragm pleural membranes are innervated by intercostal nerves that also have cutaneous distributions.
- Central diaphragm pleura is innervated by the phrenic nerve and can refer pain to the ipsilateral neck and shoulder.
- Pain is transmitted by fast-conducting A-delta fibers → sharp and well-localized pain
Clinical Presentation
- Sharp, sudden chest pain (i.e. pleuritic pain) upon inhalation and exhalation
- Worsens with increased intrathoracic pressure (e.g., deep respiration, coughing, sneezing, body trunk movement)
- Other common descriptors: dull, burning, catching, stabbing
- Can be alleviated when the pleural cavity fills with fluid, as in pleural effusion
- Dry cough
- Sneezing
- Dyspnea and rapid, shallow breathing
- Fever and/or chills if infectious
- Other signs and symptoms which present will depend on the underlying cause
Diagnosis
- Blood tests
- Test for presence of infection via elevated WBC on CBC with differential
- Antibodies can be tested to determine/rule out autoimmune conditions:
- Rheumatoid arthritis
- Systemic lupus erythematosus
- D-dimer elevation can suggest pulmonary embolism.
- Cardiac troponin is suggestive of myocardial infarction.
- Physical examination
- Pleural friction rub upon auscultation
- May also reveal other abnormal sounds if concomitant lung disease is present, such as crackles and decreased breath sounds in pneumonia
- Imaging
- Chest X-ray: may show air or fluid in the pleural space, and suggest a cause (e.g., fractured rib, malignancy)
- Consolidation can represent pneumonia.
- Pneumothorax
- A widened mediastinum is indicative of aortic dissection.
- Cardiomegaly can represent pericarditis.
- Lymphadenopathy or cavitation may suggest tuberculosis.
- CT scan: may show signs of pneumonia or the presence of a causative abscess, tumor, or blood clot within the lung with angiography
- Ultrasound: can be used to confirm pleural effusion at bedside
- Chest X-ray: may show air or fluid in the pleural space, and suggest a cause (e.g., fractured rib, malignancy)
- Electrocardiogram: used to help diagnose cardiac causes including myocardial infarction, and pericarditis
- Diagnostic procedures
- Sputum testing: test for infectious causes, especially tuberculosis
- Thoracentesis: Fluid is aspirated for laboratory analysis.
- Exudative pleural fluid shows elevated pleural fluid protein, elevated lactate dehydrogenase, or leukocytosis.
- Use Light’s criteria (see table below) to determine etiology.
- Thoracoscopy: direct visualization of the lungs and pleural cavity to visualize abnormalities and obtain a tissue sample for pathologic examination and possible microbiologic culture
| Transudate | Exudate | |
|---|---|---|
| Protein (pleural/serum) | ≤ 0.5 | > 0.5 |
| LDH (pleural/serum) | ≤ 0.6 | > 0.6 |
| Pleural LDH ≤ two-thirds upper limit of normal serum LDH | Pleural LDH > two-thirds upper limit of normal serum LDH | |
| Common causes |
|
|
Patient undergoing thoracentesis. Note that the person sits upright and leans on a table. Excess fluid from the pleural space is drained into a bag.
Image: “A person undergoing thoracentesis.” by National Heart, Lung and Blood Institute. License: Public Domain
Chest X-ray showing advanced bilateral pulmonary tuberculosis. Notice the presence of bilateral pulmonary infiltrates (white triangles) and cavitary formation (black arrows) in the right apical region.
Image: “An anteroposterior X-ray of a patient diagnosed with advanced bilateral pulmonary tuberculosis” by Centers for Disease Control and Prevention’s Public Health Image Library (PHIL). License: Public Domain
CT pulmonary angiography showing a “saddle embolus” at the bifurcation of the main pulmonary artery and thrombus burden in the lobar arteries on both sides. Can cause pleuritic symptomatology.
Image: “CT pulmonary angiography images confirming the presence of a saddle embolus” by Aung Myat and Arif Ahsan. License: CC BY 2.0
Natural History
- If inflammation resolves promptly, the pleural surfaces return to normal with no sequelae.
- If inflammation prolonged, then fibrosis with adhesions and anatomical distortions occur.
