Pleural Effusions

Pleural Effusion with Large Cardiac Silhouette

Congestive heart failure is one of the most common causes of pleural effusion, and it usually presents with a specific combination of cardiac and vascular findings. These cardiovascular changes include cardiomegaly, prominence of upper-lobe vessels, constriction of lower-lobe vessels, and prominent hilar vessels. In addition, there may be signs of interstitial edema, including fine reticular opacities, interlobular septal thickening (Kerley lines), perihilar haze, and peribronchial thickening. There may even be evidence of alveolar edema, with acinar nodules, confluent, ill-defined opacities with a perihilar distribution, and air bronchograms. The combination of cardiomegaly, pulmonary vascular changes, interstitial or alveolar edema, and pleural effusion is almost certainly diagnostic of congestive heart failure.

The pleural effusions resulting from congestive heart failure may be bilateral or unilateral. Unilateral effusions are usually on the right. Unilateral left pleural effusion in congestive failure is considered a great rarity and has even been cited as a reason to consider other diagnoses. It actually occurs in 10% to 15% of patients who develop pleural effusions secondary to congestive heart failure. Recurrent effusions caused by congestive heart failure tend to duplicate the appearance of the effusion seen in the previous episode of failure.

The combination of enlargement of the heart, pleural effusion in the absence of pulmonary vascular congestion, and signs of pulmonary interstitial or alveolar edema may be consistent with congestive heart failure. The presence of pleural effusion and cardiac enlargement alone is less specific; therefore, these require more careful review of serial examinations and correlation with clinical data to narrow the differential diagnosis ( Chart 4.2 ). Because interstitial and alveolar edema may resolve rapidly in response to diuretics, these signs of congestive heart failure may disappear, leaving residual pleural effusion and cardiomegaly. Serial chest radiographs frequently confirm this possibility.

Chronic renal failure is another cause of pulmonary edema with associated pleural effusions that is usually confirmed by correlation with the clinical history. When renal failure is the cause of pleural effusions, the associated congestive heart failure is secondary to fluid overload.

Pulmonary embolism as a cause of pleural effusions is a more difficult diagnosis to confirm. ⁸² Right-sided heart enlargement and pleural effusions may be suggestive of embolism. A patient with congestive heart failure may have right-sided heart enlargement and pleural effusion and is also at increased risk for developing a pulmonary embolism. When the effusion is atypical (e.g., predominantly left sided) or if it increases after the pulmonary edema has begun to clear, the possibility of embolism should be considered. Any combination of additional clinical information indicating the development of chest pain, hemoptysis, sudden shortness of breath, pleural friction rub, decreased arterial P o ₂ , or thrombophlebitis should be considered evidence for pulmonary embolism and thus would indicate more definitive evaluation. ³⁹⁶

The combination of cardiac silhouette enlargement caused by pericardial effusion with associated pleural effusions may be seen in patients with metastatic or inflammatory disease. A history of a current or recurrent malignant neoplasm should suggest metastatic pleural and pericardial effusions. A febrile illness with clinical findings of pericarditis or myocarditis are helpful in suggesting inflammatory diseases, in particular viral and tuberculous infections or even poststreptococcal infection (e.g., rheumatic fever).

Pleural and pericardial effusions are the most common radiologic manifestations of systemic lupus erythematosus ( Fig 4.6, A and B ). ⁶³² This diagnosis is rarely suggested by the radiologist. In the absence of other radiologic or clinical features of the common causes of pleural effusion with cardiac enlargement, this diagnosis may be considered. The pericardial effusion may be confirmed with ultrasound as an alternative to CT. Correlation with clinical and laboratory data is required to confirm the diagnosis.

Pleural Effusion with Multiple Masses

Metastatic tumors and mesothelioma may both cause pleural masses and effusion. The case in Fig. 4.7, A , shows a large, left pleural effusion with multiple pleural masses. A CT scan from the same case (see Fig 4.7, B ) reveals a large inferior chest wall mass that was obscured by the pleural effusion. This combination is not likely to result from empyema, tuberculosis, actinomycosis, or multiple myeloma. In this case, an iatrogenic pneumothorax accounts for the air-fluid level. The pleural masses were obscured by the large effusion prior to the thoracentesis. The combination of pleural effusion with pleural masses is most often confirmed with CT and is strongly suggestive of metastases. When there has been a history of asbestos exposure, mesothelioma becomes a likely explanation for unilateral pleural masses with pleural effusion.