eMedicine Specialties > Emergency Medicine > Pulmonary

Pleural Effusion

Author: C Crawford Mechem, MD, MS, FACEP, Associate Professor, Department of Emergency Medicine, University of Pennsylvania School of Medicine; Emergency Medical Services Medical Director, Philadelphia Fire Department
Contributor Information and Disclosures

Updated: Nov 13, 2009

Introduction

Background

A pleural effusion is an abnormal collection of fluid in the pleural space resulting from excess fluid production or decreased absorption.¹ It is the most common manifestation of pleural disease. The pleural space is bordered by the parietal and visceral pleurae. The parietal pleura covers the inner surface of the thoracic cavity, including the mediastinum, diaphragm, and ribs. The visceral pleura envelops all lung surfaces, including the interlobar fissures. The right and left pleural spaces are separated by the mediastinum.

The pleural space plays an important role in respiration by coupling the movement of the chest wall with that of the lungs in two ways. First, a relative vacuum in the space keeps the visceral and parietal pleurae in close proximity. Second, the small volume of pleural fluid, which has been calculated at 0.13 mL/kg of body weight under normal circumstances, serves as a lubricant to facilitate movement of the pleural surfaces against each other in the course of respirations.² This small volume of fluid is maintained through the balance of hydrostatic and oncotic pressure and lymphatic drainage, a disturbance of which may lead to pathology.³

Pathophysiology

Pleural effusion is an indicator of an underlying disease process that may be pulmonary or nonpulmonary in origin, acute or chronic.

• Normal pleural fluid has the following characteristics:
  • Clear ultrafiltrate of plasma that originates from the parietal pleura
  • pH 7.60-7.64
  • Protein content less than 2% (1-2 g/dL)
  • Fewer than 1000 WBCs per cubic millimeter
  • Glucose content similar to that of plasma
  • Lactate dehydrogenase (LDH) less than 50% of plasma
  • Sodium, potassium, and calcium concentration similar to that of the interstitial fluid
• The following mechanisms play a role in the formation of pleural effusion:
  • Altered permeability of the pleural membranes (eg, inflammation, malignancy, pulmonary embolus)
  • Reduction in intravascular oncotic pressure (eg, hypoalbuminemia, cirrhosis)
  • Increased capillary permeability or vascular disruption (eg, trauma, malignancy, inflammation, infection, pulmonary infarction, drug hypersensitivity, uremia, pancreatitis)
  • Increased capillary hydrostatic pressure in the systemic and/or pulmonary circulation (eg, congestive heart failure, superior vena cava syndrome)
  • Reduction of pressure in the pleural space, preventing full lung expansion (eg, extensive atelectasis, mesothelioma)
  • Decreased lymphatic drainage or complete blockage, including thoracic duct obstruction or rupture (eg, malignancy, trauma)
  • Increased peritoneal fluid, with migration across the diaphragm via the lymphatics or structural defect (eg, cirrhosis, peritoneal dialysis)
  • Movement of fluid from pulmonary edema across the visceral pleura
  • Persistent increase in pleural fluid oncotic pressure from an existing pleural effusion, causing further fluid accumulation

The net result of effusion formation is a flattening or inversion of the diaphragm, mechanical dissociation of the visceral and parietal pleura, and a restrictive ventilatory defect.⁴

Frequency

United States

Because pleural effusion is a manifestation of underlying disease, its precise incidence is difficult to determine. However, the incidence in the United States is estimated to be at least 1.5 million cases annually.⁵ Congestive heart failure, bacterial pneumonia, malignancy, and pulmonary embolus are responsible for most of these cases.

International

The annual incidence of pleural effusion is estimated to be 320 cases per 100,000 people in industrialized countries. A study from part of what is now the Czech Republic yielded an annual incidence of 0.32%. The most common causes, in decreasing frequency, were congestive heart failure, malignancy, parapneumonic effusions, and pulmonary emboli.⁶ When extrapolating these figures to apply to other countries, the distribution and incidence of pleural effusion causes are dependent on the population studied. For instance, in areas where tuberculosis (TB) is prevalent, a higher percentage of pleural effusions from TB may be observed.

Mortality/Morbidity

Morbidity and mortality of pleural effusions are directly related to cause, stage of disease at the time of presentation, and biochemical findings in the pleural fluid.

• Morbidity and mortality rates of patients with pneumonia and pleural effusions are higher than those of patients with pneumonia alone.
• Development of a malignant pleural effusion is associated with a poor prognosis. With the exception of breast cancer and ovarian cancer, life expectancy is often no more than 6 months after effusion onset.⁷ Patients with pleural effusions associated with carcinoma of the lung and GI tract tend to have the shortest mean survival time. Cellular and biochemical findings in the fluid may also be indicators of prognosis. For example, a lower pleural fluid pH is often associated with a higher tumor burden and worse prognosis.⁸

Race

Because pleural effusion is a manifestation of underlying disease, racial differences will most likely reflect racial variation in incidence of the causative disorder.

Sex

In general, the incidence is equal between the sexes. However, certain causes have a sex predilection.

• About two thirds of malignant pleural effusions occur in women. Malignant pleural effusions are significantly associated with breast and gynecologic malignancies.
• Pleural effusion associated with systemic lupus erythematosus is more common in women than in men.
• In the United States, the incidence of pleural effusion in the setting of malignant mesothelioma is higher in males, probably because of their higher occupational exposure to asbestos.
• Pleural effusions associated with chronic pancreatitis are more common in males, the majority of whom have alcoholism as the etiology.
• Rheumatoid effusions occur more commonly in males than in females.

Age

Pleural effusions usually occur in adults. However, they appear to be increasing in children, often in the setting of underlying pneumonia.⁹ Fetal pleural effusions have also been reported and, under certain circumstances, may be treated prior to delivery.¹⁰

Clinical

History

A detailed medical history should be obtained from all patients presenting with a pleural effusion, as this may help to establish the etiology. For example, a history of chronic hepatitis or alcoholism with cirrhosis suggests hepatic hydrothorax or alcohol-induced pancreatitis with effusion. Recent trauma or surgery to the thoracic spine raises the possibility of a cerebrospinal fluid (CSF) leak. The patient should be asked about a history of cancer, even remote, as malignant pleural effusions can develop many years after initial diagnosis. An occupational history should also be obtained, including potential asbestos exposure, which could predispose the patient to mesothelioma or asbestos pleural effusion. The patient should also be asked about medications they are taking.¹¹

The clinical manifestations of pleural effusion are variable and often are related to the underlying disease process. The most commonly associated symptoms are progressive dyspnea, cough, and pleuritic chest pain.

• Dyspnea
  • Dyspnea is the most common symptom at presentation and generally indicates the presence of a large effusion.
  • It is reported to occur in 50% of patients with malignant pleural effusions.
  • Other factors (eg, underlying lung disease, cardiac dysfunction, anemia) may also contribute to the development of dyspnea.
• Chest pain
  • Chest pain in this setting results from pleural irritation, which can aid in determining the etiology of the effusion, since most transudative effusions do not cause direct pleural irritation. Its presence raises the likelihood of an exudative etiology such as pleural infection, mesothelioma, or pulmonary infarction.¹²
  • Pain may be mild or severe. It is typically described as sharp or stabbing and is exacerbated with deep inspiration.
  • Pain may be localized to the chest wall or referred to the ipsilateral shoulder or upper abdomen, usually because of diaphragmatic involvement.
  • Pain often diminishes in intensity as the pleural effusion increases in size.
• Other symptoms occurring with pleural effusions are associated with the underlying disease process.
  • Increasing lower extremity edema, orthopnea, and paroxysmal nocturnal dyspnea may all occur with congestive heart failure.
  • Night sweats, fever, hemoptysis, and weight loss should suggest tuberculosis (TB).
  • Hemoptysis also raises the possibility of malignancy, other endotracheal or endobronchial pathology, or pulmonary infarction.
  • An acute febrile episode, purulent sputum production, and pleuritic chest pain may occur in patients with an effusion associated with pneumonia.

Physical

Physical findings are variable and depend on the volume of the pleural effusion. Generally, there are no physical findings for effusions smaller than 300 mL. With effusions larger than 300 mL, findings may include the following:

• Dullness to percussion
• Decreased tactile fremitus
• Asymmetric chest expansion, with diminished or delayed expansion on the side of the effusion: Dullness to percussion, decreased tactile fremitus, and asymmetric chest expansion are the most reliable physical findings of pleural effusion.^13,14
• Diminished or inaudible breath sounds
• Egophony ("e" to "a" changes) at the most superior aspect of the pleural effusion
• Pleural friction rub
• Other findings that provide clues to the etiology of the effusion include the following:
  • Peripheral edema, distended neck veins, and S ₃ gallop, suggestive of congestive heart failure
  • Edema may also be a manifestation of nephrotic syndrome; pericardial disease; or, combined with yellow nails, the yellow nail syndrome.
  • Cutaneous changes with ascites, suggestive of liver disease
  • Evidence of malignancy such as lymphadenopathy or palpable mass¹¹

Causes

Because pleural effusion formation is a manifestation of underlying disease as opposed to being a disease process in itself, many underlying etiologies may exist.^15,11 Pleural effusions are generally classified as transudates or exudates, based on the mechanism of fluid formation and pleural fluid chemistry. Transudates result from an imbalance in oncotic and hydrostatic pressures, whereas exudates are the result of inflammation of the pleura or decreased lymphatic drainage. In some cases, the pleural fluid may have some characteristics of both transudatives and exudatives. The etiologic spectrum of pleural effusion is extensive. However, most pleural effusions are caused by congestive heart failure, pneumonia, malignancy, or pulmonary embolism.

Transudates

• Systemic factors that govern formation of transudates include increased systemic and/or pulmonary capillary hydrostatic pressure (elevated pulmonary capillary wedge pressure of 10 cm H₂ O or higher), decreased colloid osmotic pressure in the systemic circulation, or both. Pleural membranes are intact and are not involved in pathogenesis of the fluid formation. The permeability of pleural capillaries to proteins is normal.
• Conditions associated with transudate formation include the following:
  • Congestive heart failure
  • Cirrhosis
  • Nephrotic syndrome
  • Urinothorax (usually due to obstructive uropathy)
  • Myxedema
  • Cerebrospinal fluid leaks to the pleura (generally in the setting of ventriculopleural shunting, or trauma or surgery to the thoracic spine)
  • Peritoneal dialysis
  • Duropleural fistula (rare but may be a complication of spinal cord surgery)
  • Extravascular migration of central venous catheter¹⁶
  • Glycinothorax (a rare complication of bladder irrigation with 1.5% glycine solution following urologic surgery)

Exudates

• Local factors governing formation of exudates include altered permeability of pleural membranes, increased capillary wall permeability or vascular disruption, and decreased or complete obstruction of lymphatic drainage of pleural space. Pleural membranes are involved in pathogenesis of the fluid formation. Permeability of pleural capillaries to proteins is high, resulting in an elevated protein content.
• Conditions associated with exudates formation include the following:
  • Malignancy (most commonly lung or breast cancer, lymphoma, and leukemia; less commonly ovarian carcinoma, stomach cancer, sarcomas, melanoma)¹⁷
  • Pneumonia (often associated with treatment failure)¹⁸
  • Tuberculosis
  • Pulmonary embolism
  • Fungal infection
  • Pancreatic pseudocyst
  • Intra-abdominal abscess
  • Status-post coronary artery bypass graft surgery
  • Postcardiac injury syndrome
  • Pericardial disease
  • Meigs syndrome (benign pelvic neoplasm with associated ascites and pleural effusion)
  • Ovarian hyperstimulation syndrome
  • Rheumatoid pleuritis
  • Systemic lupus erythematosus¹⁹
  • Drug-induced pleural disease (see Pneumotox On Line for an extensive list of drugs that can cause pleural effusion)
  • Asbestos-related pleural disease
  • Yellow nail syndrome (yellow nails, lymphedema, and pleural effusions)
  • Uremia
  • Trapped lung (localized pleural scarring with the formation of a fibrin peel prevents incomplete lung expansion, at times leading to pleural effusion)
  • Chylothorax (acute illness with elevated triglycerides in pleural fluid)
  • Pseudochylothorax (chronic condition with elevated cholesterol in pleural fluid)
  • Extravascular migration of central venous catheter
  • Fistula (pancreaticopleural, ventriculoperitoneal, ventriculopleural, biliopleural, gastropleural)

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