Pleural Disorders
pleura is a large, thin sheet of tissue that wraps around the outside of your lungs and lines the inside of your chest cavity. Between the layers of the pleura is a very thin space. Normally it's filled with a small amount of fluid. The fluid helps the two layers of the pleura glide smoothly past each other as your lungs breathe air in and out. Pleural fluid volume is maintained by a balance between fluid production and removal, and changes in the rates of either can result in the presence of excess fluid, traditionally known as a pleural effusion.

Disorders of the pleura include
•    Pleurisy - inflammation of the pleura that causes sharp pain with breathing
•    Pleural effusion - excess fluid in the pleural space
•    Pneumothorax - buildup of air or gas in the pleural space
•    Hemothorax - buildup of blood in the pleural space

Many diseases affect the pleural space in both adults and children, including common diseases such as pneumonia, breast cancer, and heart failure. Pleural disease is, therefore, often a secondary effect of another disease process. Pleural effusion is the most common manifestation of pleural disease and a common presentation of other conditions such as heart failure or kidney failure. It is estimated that a million Americans develop a pleural effusion each year. “Pleurisy” is any inflammatory condition of the pleura. Because the pleura is richly supplied with nerves, pleurisy can be quite painful. Usually, when the pleural space is involved in pneumonia or lung cancer, the patient is sicker and has a worse prognosis than in the absence of pleural involvement.

Many different conditions can cause pleural problems. Viral infection is the most common cause of pleurisy. The most common cause of pleural effusion is congestive heart failure. Lung diseases, like COPD, tuberculosis, and acute lung injury, cause pneumothorax. Injury to the chest is the most common cause of hemothorax. Treatment focuses on removing fluid, air, or blood from the pleural space, relieving symptoms, and treating the underlying condition.

A common cause of pleural disease is cancer. It is estimated that malignant pleural effusion affects 150,000 people per year in the United States. Most patients with pleural effusion come to the doctor complaining of shortness of breath, which is caused by fluid accumulating in the chest and compressing the Lung. Once a malignant pleural effusion is diagnosed, the prognosis is very poor, with patients living only another four months on average.

 

 

In this CT scan, mesothelioma is shown growing extensively in the pleural space (arrows) and is
completely surrounding the lung on one side of the chest. The thickened pleura can be appreciated
in comparison to the same area on the opposite side, which is normal. Note how the chest on the
side of the mesothelioma is smaller than the opposite side; mesothelioma characteristically shrinks
the chest and constricts the lung, making it difficult to take a breath. One can also appreciate how
difficult it would be to treat a tumor that spreads in this way

 



Prevalence
Pleural disease, specifically pleural effusions, is one of the more common clinical problems encountered by the internist. Estimates of the incidence of pleural effusions vary, with some estimating an annual incidence of up to 1 million in the United States. The more common causes of transudative effusions are congestive heart failure and hypoalbuminemic states (e.g., cirrhosis), and those of exudative effusions are malignancy, infection (e.g., pneumonia), and pulmonary embolism.
Pathophysiology
The accumulation of pleural fluid can usually be explained by increased pleural fluid formation or decreased pleural fluid absorption, or both. Increased pleural fluid formation can result from elevation of hydrostatic pressure (e.g., congestive heart failure), decreased colloid osmotic pressure (e.g., cirrhosis, nephrotic syndrome), increased capillary permeability (e.g., infection, neoplasm), passage of fluid through openings in the diaphragm (e.g., cirrhosis with ascites), or reduction of pleural space pressures (e.g., atelectasis). Decreased pleural fluid absorption can result from lymphatic obstruction or from elevation of systemic venous pressures resulting in impaired lymphatic drainage (e.g., superior vena cava [SVC] syndrome).
The presence of fluid in the normally negative-pressure environment of the pleural space has a number of consequences for respiratory physiology. Pleural effusions produce a restrictive ventilatory defect and also decrease the total lung capacity, functional residual capacity, and forced vital capacity.3 They can cause ventilation-perfusion mismatches and, when large enough, compromise cardiac output.
Signs and symptoms
Many patients are asymptomatic on the discovery of a pleural effusion. When present, symptoms are usually due to the underlying disease process. Pleuritic chest pain indicates inflammation of the parietal pleura (because the visceral pleura is not innervated and thus not sensitive to pain). Other symptoms include dry, nonproductive cough and dyspnea. Physical examination findings that can reveal the presence of an effusion are reduced tactile fremitus, dull or flat note on percussion, and diminished or absent breath sounds on auscultation. It is also important to note the presence of other clues that can point to the cause of the effusion (e.g., signs of heart failure, breast masses).
Diagnosis
Imaging Studies
Chest Radiography
The posteroanterior and lateral chest radiographs are still the most important initial tools in diagnosing a pleural effusion (Figure 1). Free pleural fluid gravitates to the more dependent portions of the space; thus, most fluid collects around the inferior surface of the lung posteriorly, spilling out laterally and anteriorly as the amounts increase. About 50 mL of fluid is needed to be visible on the lateral radiograph as a meniscus posteriorly, and when more than 500 mL is present, the meniscus usually obscures the entire hemidiaphragm. The lateral decubitus films help in differentiating free fluid from loculated fluid (that which is confined by fibrous pleural adhesions).
Ultrasound
Ultrasound is useful both as a diagnostic tool and as an aid in performing thoracentesis. Its major advantage over conventional radiography is its ability to differentiate between solid and liquid components and thus assist in identifying pleural fluid loculations. It is also valuable in detecting subpulmonic or subphrenic pathology.
Computed Tomography
Cross-sectional computed tomography (CT) (Figure 2) helps distinguish anatomic compartments more clearly (e.g., the pleural space from lung parenchyma). This modality is useful as well in distinguishing empyema (split pleura sign) from lung abscess, in detecting pleural masses, and in outlining loculated fluid collections.

Other Diagnostic Modalities
Pleural Biopsy
The use of an Abrams needle to obtain specimens from the parietal pleura has become less common with the increasing availability of improved serum markers and thoracoscopy. At present, a needle biopsy of the pleura is used mainly to diagnose tuberculous pleuritis when other markers (e.g., adenosine deaminase) are negative.
Thoracoscopy
Invasive techniques for the diagnosis of pleural effusions have gained more popularity with the advent of video-assisted technology. Thoracoscopy offers the advantages of visual evaluation of the pleura, direct tissue sampling, and therapeutic intervention (e.g., dissecting loculations and pleurodesis). Medical thoracoscopy (performed by pulmonologists under conscious sedation) and video-assisted thoracoscopic surgery (VATS), which is performed by surgeons under general anesthesia, are indicated for diagnosing pleural effusions that have remained undiagnosed despite previous, less-invasive tests (e.g., thoracentesis).

Treatment and outcomes
Therapeutic Thoracentesis
Drainage of a pleural effusion is indicated in complicated parapneumonic effusions or empyema, for symptomatic relief of dyspnea, and to evaluate underlying lung parenchyma. The current guidelines proposed by the ACCP for the treatment of parapneumonic effusions categorize the risk of poor outcome as well as the need to drain the effusion based on the pleural space anatomy, pleural fluid bacteriology (culture and Gram stain), and pleural fluid chemistry (pH).
Therapeutic thoracentesis may be repeated if indicated; however, more definitive therapy (e.g., pleural sclerosis; see following) is usually needed to treat recurrent symptomatic pleural effusions. At any one time, no more than 1 L to 1.5 L of fluid should be removed (unless pleural space pressure is monitored) to avoid re-expansion pulmonary edema and post-thoracentesis shock. Supplemental oxygen is probably of benefit as well, because post-thoracentesis decreases in arterial oxygenation have also been reported, the magnitude and duration of which roughly correlate with the amount of fluid removed.
Pleural Sclerosis and Fibrinolytics
The use of a sclerosing agent to produce a chemical serositis and subsequent fibrosis of the pleura is indicated in recurrent symptomatic malignant effusions. Agents such as talc, doxycycline, bleomycin, and quinacrine have been used. All fluid must be drained initially and that full expansion of the underlying lung (usually via a tube thoracostomy) is essential before proceeding with sclerosis. Failure of treatment is usually due to the inability to approximate the pleural surfaces during administration of the agent. With proper technique, however, doxycycline sclerosis has been reported to be 80% to 90% effective.
Randomized, controlled trials have shown that fibrinolytics (urokinase or streptokinase instilled via a tube thoracostomy) improved fluid drainage and chest radiograph findings significantly, and it was an effective treatment for managing parapneumonic effusions.
Surgery
The inadequacy of conventional drainage strategies has led the ACCP consensus panel to recommend video-assisted thoracoscopic surgery (VATS) and thoracotomy as acceptable approaches to managing patients with complicated pleural effusions. Parietal pleurectomy and decortication of the visceral pleura are definitive procedures with excellent response rates. Morbidity and mortality rates remain high, however, and the patient's general medical condition, expected long-term prognosis, and baseline lung function should be considered before proceeding with surgery.