Malignant fluid collections within the pleura and/or pericardium are common oncologic dilemmas. These effusions are frequently symptomatic and, in the case of the pleural space, may be the presenting sign of cancer. In other patients, they represent markers of recurrent, disseminated, or advanced disease. Pleural or pericardial effusions require rapid diagnosis and, if symptomatic, expeditious management. External drainage usually leads to a discrete diagnosis and temporarily relieves symptoms, yet definitive therapy is often more complex and may involve interventional radiology, cardiology, and thoracic surgery, as well as medical and radiation oncology. Permanent drainage and/or obliteration of the pleural or pericardial space are the keys to definitive treatment of the effusion and will provide long-standing palliation. Clinicians must acknowledge the grave prognosis facing most patients with these conditions—as their malignancies are, by definition, advanced—and must strive for the least morbid route toward diagnosis and durable palliation.
Malignant Pleural Effusions Pathophysiology
The pleural space has a dynamic physiology. In its normal state, the pleura may contain between 10 and 40 mL of hypoproteinemic plasma filtrate. Most pleural fluid originates in the capillary bed of the parietal pleura. Investigators estimate between 5 and 10 L of fluid is produced each day. All but about 30 mL of this fluid is reabsorbed by subpleural pulmonary venous capillaries and, to a lesser extent, by pleural lymphatics. mycanadianpharmacy.com
Malignant pleural effusions may arise from a variety of cancer-related events. Pulmonary parenchymal tumors (primary or metastatic) may erode the visceral pleura, spilling cells and disrupting the normal resorptive flow of fluid from the parietal to the visceral surface. Alternatively, the parietal and visceral pleura themselves are common sites of metastatic seedings. The presence of tumor here results in increased capillary permeability due to inflammation or overt endothelial disruption. Tumor deposits in the visceral pleura obstruct the lymphatic drainage necessary to maintain normal pleural fluid volume homeostasis. In addition, the existence of comorbid patient factors not directly related to pleural cancer can exacerbate a pleural effusive process. Such contributing factors, outlined in Table 1, were enumerated by Ruckde-schel in an overview of malignant effusions.
Table 1—Nonpleural Pathologic Conditions Contributing to MPEs
|Conditions Mediastinal nodal involvement by tumor|
|Coexistent obstructing pneumonia|
|Prior mediastinal/thoracic radiotherapy|
|Coexistent pericardial restriction/constriction/effusion|
|Congestive heart failure|
|Coexistent rheumatologic disorders (serositis)|