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Make the Diagnosis: Pleural Effusion

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Prior Probability

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The prevalence of pleural effusion depends on the underlying conditions or the clinical setting. For example, in patients with pneumonia, 20%-57% have parapneumonic effusions while decompensated congestive heart failure (CHF) creates pleural effusions in the majority of patients (87%).1 Among medical intensive care unit patients, about 8.4% have effusions, whereas pleural effusions exist in 17% of dyspneic emergency department patients.2

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Population in Whom Pleural Effusion Should Be Considered

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The leading underlying diagnoses associated with pleural effusions are CHF, pneumonia, malignancy, pulmonary embolus, viral disease, coronary artery bypass surgery, and cirrhosis with ascites.3 The clinical examination is used not so much to determine whether the patient has a pleural effusion but to identify patients that require diagnostic imaging to rule out a pleural effusion.

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Assessing the Likelihood of Pleural Effusion

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The physician should perform palpation, percussion, and auscultation of the chest when pleural effusion is considered. Dullness to conventional percussion and reduced tactile fremitus are the best findings for identifying patients with pleural effusion (Table 71-1). Experts recommend having the patient say “boy” or “toy” to create a low-pitched vibration that can be felt by palpation to assess for tactile vocal fremitus.

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Table Graphic Jump Location
Table 71-1Useful Findings for Diagnosing Pleural Effusion
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The absence of reduced tactile vocal fremitus (likelihood ratio [LR] 0.21 (0.12-0.37)) may be the most useful findings for ruling out pleural effusion but has only been reported in 1 high-quality studies.4

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Reference Standard Tests

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While demonstration of pleural fluid on thoracentesis is the true reference standard, radiographic imaging is typically accepted as confirmatory. Pleural fluid becomes visible on the upright lateral radiograph at a volume of approximately 50 mL as a meniscus in the posterior costophrenic sulcus. The meniscus becomes visible on the posterior-anterior projection at a volume of about 200 mL.5 Thoracentesis is performed to determine the laboratory characteristics of the effusion, rather than to determine whether a pleural effusion is present.

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When patients have CHF, about 60% will have bilateral effusions that can be asymmetric. When there is asymmetry, a unilateral right-sided effusion or a right-side effusion larger than the left has a summary prevalence of 47% (95% confidence interval [CI], 30%-65%), while a left-side predominance occurs in only 19% (95% CI, 12%-26%) of patients with CHF-associated effusions.

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References

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Kataoka  H. Pericardial and pleural effusions in decompensated chronic heart failure. Am Heart J. ...

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