MKSAP: 57-year-old man with a right-sided pleural effusion

Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 57-year-old man is evaluated in follow-up for a right-sided pleural effusion. He initially presented with increasing dyspnea and a constant dull ache on his right side. He also has lost 9.1 kg (20.0 lb) over the last 6 months. Medical history is otherwise unremarkable, and he takes no medications. He has never smoked and is employed as an auto mechanic.

Initial chest radiograph showed a moderate-sized, free-flowing pleural effusion on the right; the left lung field was unremarkable. Thoracentesis showed 3500/µL (3.5 × 109/L) nucleated cells with 45% lymphocytes and an exudative profile with negative Gram stain, culture, and cytology. Chest CT following thoracentesis showed no parenchymal lesions but several areas of pleural thickening. A repeat thoracentesis performed 2 weeks later showed similar results, also with negative cultures and cytology.

On physical examination, temperature is 36.7 °C (98.1 °F), blood pressure is 128/72 mm Hg, pulse rate is 81/min, and respiration rate is 18/min; BMI is 23. There is no jugular venous distention. Heart sounds are normal with no murmurs. Dullness to percussion and decreased breath sounds are noted over the lower third of the right hemithorax. The left lung is clear to auscultation. No lower extremity edema is noted.

Repeat chest radiograph shows reaccumulation of the right pleural effusion.

Which of the following is the most appropriate diagnostic test to perform next?

A: Bronchoscopy
B: Large-volume pleural fluid cytology
C: PET/CT scanning
D: Thoracoscopy

MKSAP Answer and Critique

The correct answer is D: Thoracoscopy.

The most appropriate diagnostic test to perform next is thoracoscopy. This patient has an unexplained unilateral exudative effusion. Owing to his occupation as an auto mechanic, he has a history of potential asbestos exposure (car brakes previously contained asbestos). This potential exposure increases his risk for mesothelioma, which is suggested by his clinical presentation (exudative pleural effusion, chronic chest pain, weight loss) and imaging findings (pleural thickening). Thoracoscopy allows for the direct visualization of the pleural surface and enables biopsy of pleural sites likely to have a high diagnostic yield. It has a diagnostic sensitivity for malignant disease of greater than 90%. Thoracoscopy is indicated in this patient in whom imaging and thoracentesis have not achieved a diagnosis, which occurs relatively frequently with mesothelioma.

Because endobronchial lesions are rarely seen in mesothelioma, bronchoscopy would not be an appropriate next diagnostic study.

Repeat pleural fluid cytology is not appropriate because this patient has already had two negative studies. The overall mean sensitivity of pleural fluid cytology for identifying malignant disease is approximately 60%. Approximately 65% of positive results are obtained on the initial thoracentesis. The diagnostic yield from sending more than two samples is very low. One study demonstrated an additional yield of 27% on the second sample and only 5% on the third.

PET/CT scanning is a useful tool for staging disease, particularly for identifying extrathoracic disease. However, it is not a preferred initial diagnostic study because both malignant and nonmalignant pleural thickening can be avid for fluorodeoxyglucose and yield a positive finding on this study.

Key Point

  • If repeat pleural fluid cytology is negative and the suspicion for malignancy is high in an exudative effusion, thoracoscopy is the next step in the evaluation; it has a diagnostic sensitivity for malignant disease of greater than 90%.

This content is excerpted from MKSAP 17 with permission from the American College of Physicians (ACP). Use is restricted in the same manner as that defined in the MKSAP 16 Digital license agreement. This material should never be used as a substitute for clinical judgment and does not represent an official position of ACP. All content is licensed to on an “AS IS” basis without any warranty of any nature. The publisher, ACP, shall not be liable for any damage or loss of any kind arising out of or resulting from use of content, regardless of whether such liability is based in tort, contract or otherwise.

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