IN DETECTING AND EVALUATING pleural effusion, technology has not replaced clinical skills. Yet, despite centuries of lore, data are limited on the role of the physical examination and on its accuracy compared with other noninvasive tests such as conventional chest radiography or ultrasonography.
The following is an overview of the value of the clinical history and physical examination in detecting pleural effusion and a brief review of the available information regarding its accuracy compared with other diagnostic methods.
POTENTIAL CAUSES ARE MANY
The pleurae consist of two membranes that protect the lungs, allow them to move, contribute to their shape, and prevent the alveoli at the pleural surface from becoming overdistended. Between the visceral pleura (covering the lung) and the parietal pleura (covering the diaphragm and the chest wall) is the pleural space.
In healthy adults, the pleural space contains an estimated 5 to 10 mL of pleural fluid (0.1 mg/kg body weight).1 Pleural effusion is an accumulation of an abnormal amount of fluid in the pleural space.
Although the potential causes are many, the most common are congestive heart failure, pneumonia (40% of patients hospitalized with pneumonia have pleural effusion),2,3 cancer, and pulmonary embolism.4
Because many diseases affecting different organs can cause a pleural effusion, we cannot overemphasize the importance of a thorough history and physical examination to uncover clues that will help identify its cause and narrow the diagnostic workup. For example, significant weight loss and cachexia could be due to cancer, and joint, skin, or eye symptoms could be due to a connective tissue disorder.
A thorough review of the patient’s medications is mandatory, since several medications (eg, amiodarone [Cordarone], methotrexate [Rheumatrex, Trexall], and nitrofurantoin [Macrobid]) can be associated with exudative effusions. In addition, the patient’s occupational history must be ascertained, since exposure to asbestos can raise the suspicion of a malignant disease of the pleura such as mesothelioma.
SYMPTOMS ARE NEITHER SENSITIVE NOR SPECIFIC
The symptoms of pleural effusion are neither sensitive nor specific, and many patients have manifestations of the underlying process but not of the effusion itself. The most common symptoms directly related to effusion are cough, dyspnea, and pleuritic chest pain.5
Cough. Many patients with a pleural effusion have a dry, nonproductive cough, a consequence of inflammation of the pleurae or compression of the bronchial walls. Although this symptom is rarely helpful in diagnosing a pleural effusion, if accompanied by purulent sputum it suggests pneumonia, and if complicated by hemoptysis it suggests cancer or pulmonary embolism.
Dyspnea is a consequence of a combination of a restrictive lung defect, a ventilation-perfusion mismatch, and a decrease in cardiac output. Although large pleural effusions reduce lung volume and are generally associated with dyspnea, the symptoms may be out of proportion to the size of the effusion, and patients with small to moderate effusions may also have shortness of breath if their baseline lung function is poor.2
Chest pain accompanying a pleural effusion suggests inflammation of the parietal pleura,6 but could be due to cancer in the chest wall and ribs—or to a benign disease of the thoracic wall such as rib fracture or costo-chondritis.
Pain of pleural origin can remain localized to the adjacent area of the chest, but sometimes it is referred to other areas. If the diaphragmatic pleura is involved, the pain is in many cases referred to the ipsilateral shoulder.5 Pain may also be referred to the abdomen.
Pleuritic chest pain is described as being worse with deep inspiration or when lying down. It is common in patients with pulmonary embolism, parapneumonic effusion, or viral pleurisy, but it can also occur in patients with pneumothorax or pericarditis. A dull, aching chest pain may be due to an underlying pleural malignancy.7
PHYSICAL EXAMINATION: LONG TRADITION, FEW DATA
Our knowledge of the role of physical examination in detecting pleural effusion is still based mostly on expert opinion and on small case series.8,9
TABLE 1 lists the most common physical signs of pleural effusion10–15; TABLE 2 lists some less common (anecdotal) signs.11,14–16 The sensitivities and specificities of the different signs in detecting pleural effusion have not been extensively studied. The limited data suggest that clinical acumen is less accurate than ultrasonography of the chest, but certain reports found it about as accurate as standard chest radiography.
Diacon et al17 assessed the accuracy of clinical examination and ultrasonography for selecting pleural puncture sites in 67 patients. Compared with ultrasonography as the gold standard, clinical examination had a sensitivity of 76%, a specificity of 60%, a positive predictive value of 85%, and a negative predictive value of 45%.