Mechanisms of Injury
- Normally, the pleural space only contains a small amount of fluid that is not radiographically apparent.
- Transudative pleural effusions result from alteration of hydrostatic and oncotic factors that increase the formation or decrease the absorption of pleural fluid (e.g., increased mean capillary pressure [heart failure] or decreased oncotic pressure [cirrhosis or nephrotic syndrome]).
- Exudative pleural effusions occur when damage or disruption of the normal pleural membranes or vasculature (e.g., tumor involvement of the pleural space, infection, inflammatory conditions, or trauma) leads to increased capillary permeability or decreased lymphatic drainage.
- Parapneumonic effusions are exudates that develop secondary to pulmonary infections. Patients with pneumonia and a pleural effusion should undergo rapid diagnostic testing because an infected pleural space (empyema) needs to be treated without delay.
- Malignant pleural effusions arise from tumor involvement of the pleura or mediastinum. Patients with malignancy are also at increased risk for pleural effusions from postobstructive pneumonia, pulmonary emboli, chylothorax, and drug or radiation reactions.
- While pleural effusion occurs in a vast array of disease states, 90% of pleural effusions are the result of only five diseases.
- Congestive heart failure (36%)
- Pneumonia (22%)
- Malignancy (14%)
- Pulmonary embolism (11%)
- Viral disease (7%)
- The underlying cause of the effusion usually dictates the symptoms, although patients may be asymptomatic.
- Pleural inflammation, abnormal pulmonary mechanics, and worsened alveolar gas exchange produce symptoms and signs of disease.
- Inflammation of the parietal pleura leads to pain in local (intercostal) involved areas or referred (phrenic) distributions (shoulder).
- Dyspnea is frequent and may be present and out of proportion to the size of the effusion.
- Cough can occur.
- Chest examination is notable for dullness to percussion, decreased or absent tactile fremitus, and decreased breath sounds.
- Tracheal shift to the contralateral side or an ipsilateral pleural rub may be present.
History and Physical Examination
- The clinical setting is crucial to establishing a proper diagnosis. A definitive diagnosis based solely upon pleural fluid analysis is possible in the minority of pleural effusions.
- History or physical examination findings suggestive of congestive heart failure, malignancy, pneumonia, pulmonary mbolism, myocardial infarction, surgery, cirrhosis, or rheumatologic arthritis provide important clues to the underlying diagnosis.
Laboratory and Imaging Studies
- Pleural effusions are typically detected by chest radiography as blunting of the costophrenic angle or opacification of the base of the hemithorax without loss of volume of the hemithorax (which would suggest atelectasis), and may be accompanied by air bronchograms (which would suggest an alveolar filling process such as pneumonia).
- Prior to invasive diagnostic or therapeutic procedures, the patient should undergo imaging to confirm the presence and size of the effusion. Preferred modalities include:
- Decubitus chest radiography showing layering fluid will confirm the presence of pleural effusion and demonstrates that at least a portion of the fluid is not loculated.
- Thoracic ultrasonography is one of the best modalities to assess for pleural fluid loculations. Ultrasonography can also rovide real-time guidance for pleural procedures and can reduce both the complication and failure rate
- of thoracentesis.
- Computed tomography of the chest with contrast helps differentiate pleural fluid from lung masses and atelectatic lung, and helps define the extent of pleural thickening, pleural nodularity, and other associated findings.
- Pleural fluid analysis:
- Thoracentesis can be performed safely at the bedside, in the absence of disorders of hemostasis, on effusions that extend >10 mm from the inner chest wall on a lateral decubitus film. Loculated effusions can be localized with ultrasonography or CT scan. Proper technique and sonographic guidance minimize the risk of pneumothorax and other complications. Repeat thoracentesis increases the diagnostic yield.
- Serum lactate dehydrogenase (LDH), protein, pH, glucose and albumin should be measured within hours of the thoracentesis to allow appropriate comparison.
- Pleural fluid appearance Red-tinged pleural effusions indicate the presence of blood.
- In exudative pleural effusions, serosanguineous fluid is usually not helpful in narrowing the diagnosis. If the blood is due to thoracentesis, the degree of discoloration should clear during the aspiration.
- Bloody pleural fluid usually indicates the presence of malignancy, pulmonary embolism (PE), or trauma.
- The presence of gross blood should lead to the measurement of a pleural fluid hematocrit. Hemothorax is defined as a pleural fluid to blood hematocrit ratio of >0.5, and chest tube drainage
- Transudates resolve with treatment of the underlying heart, kidney, or liver disease. Uncommonly, more aggressive pproaches including pleurodesis and shunts are required.
- Parapneumonic effusions and empyema should be managed with tube drainage when indicated based on the size, gross appearance, or biochemical analysis of the pleural fluid or the presence of loculations Multiple tubes are sometimes required to adequately drain the pleural space.
- Failure to adequately and quickly drain a complicated parapneumonic effusion can lead to organization of the pleural fluid and formation of a thick pleural which may necessitate surgical removal known as decortication.
- Malignant pleural effusions
- Observation without invasive interventions may be appropriate for some patients with malignant pleural effusions.
- Therapeutic thoracentesis may improve patient comfort and relieve dyspnea. The rapid removal of more than 1 L of pleural fluid may rarely result in re-expansion pulmonary edema, especially if the lung is unable to re-expand. The subjective response to drainage and the rate of fluid reaccumulation should be monitored.
- Repeated thoracenteses are reasonable if they achieve symptomatic relief and if fluid reaccumulation is slow. Unfortunately, 95% of malignant effusions will recur with a median time to recurrence of less than a week. When frequent or repeated thoracentesis is required for effusions that reaccumulate, early consideration should be given to tube drainage with pleurodesis or placement of a chronic indwelling pleural catheter.
- Chemical pleurodesis is an effective therapy for recurrent effusions. This treatment is recommended in patients whose symptoms are relieved with initial drainage but who have rapid reaccumulation of fluid.
- Talc pleurodesis is effective and inexpensive. Fever and hypoxia are common following instillation of talc into the pleural space, and respiratory failure has been described on occasion. Overall efficacy is similar for talc slurry delivered via chest tube versus dry talc insufflated during thoracoscopy. Insufflated dry talc has added benefit for patients with lung or breast cancer.
- Doxycycline or minocycline can also be instilled into the pleural space via a chest tube. Pain is more prevalent and severe following doxycycline and minocycline than following talc.
- Bleomycin appears to be less effective and more expensive than other drugs.
- Systemic analgesics and the administration of lidocaine in the sclerosing agent solution help to decrease the appreciable discomfort associated with the procedure.
- If the chest tube drainage remains high (>100 mL/d) more than 2 days after the initial pleurodesis, a second dose of the sclerosing agent can be administered.
- Chronic indwelling pleural catheters can provide good control of effusion-related symptoms via intermittent drainage. The Pleurx catheter is better at controlling symptoms than doxycycline administered via a chest tube. Furthermore, repeated drainage via a Pleurx catheter leads to pleurodesis in roughly 50% of patients, allowing the catheter to be removed.
- Pleurectomy or pleural abrasion requires thoracic surgery and should be reserved for patients with a good prognosis who have had ineffective pleurodesis or inadequate response to chronic pleural drainage.
- Chemotherapy and mediastinal radiotherapy may control effusions in responsive tumors, such as lymphoma or small-cell bronchogenic carcinoma, although it has poor efficacy in metastatic carcinoma.